History of Cement Manufacturing Technology

1
Takashi Shimoda

Abstract
The Japanese cement industry today produces the best quality portland cement with the lowest energy consumption and highest
labor productivity in the world. In addition, since the 1990s, the industry has been demonstrating a new role for the cement industry
by using industrial and municipal waste as Alternative Fuel and Raw Materials (AFR). The Japanese cement industry has thus cometo pursue two industrial missions: the manufacture of quality cement and contribution to a sustainable society.
The cement industry in Japan started in the 1870s when the Japanese government constructed the country’s first cement plant, inTokyo, which relied on European technology and equipment. For the next 90 years, up until the 1960s, Japan imported newtechnology and equipment from Europe and the U.S.A. Rotary kilns, tube mills, vertical mills, kiln waste-gas boilers/generators,
air-quenching coolers, and blending silos were among those imports. Also, major imports of technology included the addition of
gypsum in cement, cement quality standards, and several types of special cement such as high-early-strength, low-heat,
blast-furnace-slag, fly-ash, and silica cements.
During that time, in 1959, Onoda Cement Co. Ltd. (now Taiheiyo Cement Co.) developed a new cement manufacturing process
called the “New Calcined Lime Burning Process (NCB).” With this process, limestone is separately calcined in specially designed
shaft kilns, then mixed with other raw materials and sent to a rotary kiln for clinker formation. This produced the astonishing result ofa four-fold expansion in unit volume output from the same kiln. The NCB process is considered the first major “Japan original”
cement manufacturing technology.
In the 1960s, the Suspension Preheater (SP) kiln process was introduced from Germany. This process rapidly came to prevail inJapan because of its high energy efficiency, excellent upscalability, and prolonged operation period.
Soon after the introduction of the SP process, Japanese cement manufacturers and plant builders, observing the NCB process,began competing with each other to develop a New Suspension Preheater (NSP) process, assuming that unit volume output would
greatly increase if a calciner were installed at the bottom of the preheater. These efforts produced fruit in early 1970s. A couple ofcompanies successfully developed NSP processes of their own. Each type of NSP equally achieved higher energy efficiency, better
upscalability, and a longer operation period than the SP process. Consequently, the NSP process made the Japanese cement
industry the most energy efficient in the world.
The success of NSP stimulated Japanese engineers to innovative further with cement manufacturing technology. The O-SEPA
separator, the OK vertical grinding mill, and the vertical pre-grinding mill are among their inventions since the 1980s.
Japanese cement chemists, too, have made a great contribution to the cement industry’s progress and development. In 1968,
Japan hosted the 5th International Symposium on the Chemistry of Cement. Through this epoch-making conference, Japanese
cement chemists played a major role in elucidating the scientific basis for the formation of clinker minerals and the hydration of
cement, applying the very latest modern technology such as Electron Probe Micro Analysis (EPMA). In the 1970s, Dr. Yoshio Ono of
Onoda Cement created a microscopic method to estimate clinker quality onsite. This method, called the Ono Method, is now
recognized worldwide.
The Japanese cement industry began using AFR as early as the 1960s for the purpose of reducing manufacturing costs. Since
the late 20th century, however, the industrial and municipal waste problem has become a center of focus along with growing
concerns about the global sustainability of natural resources. The Japanese cement industry realigned its position on the use of AFRfrom mere reduction of manufacturing costs to the even more positive one of contributing to sustainability through greater use ofalternative fuels and more recycling of raw materials. In pursuing this new mission, the industry has been developing innovative
processes and equipment in order to make greater use of a wider range of AFR. To date, several processes and kinds of equipment
have been successfully developed, such as the Chloride Bypass Process, the Ash Washing Process, the Biochemical Conversion
Process for household waste (AK System) and Ecocement. These recycling practices are now widely recognized internationally.
Cement consumption in Japan fully matured in the middle of 1990s; however, the Japanese cement industry and its engineers
have great hopes for a future in which the industry is positioned at the core of the sustainable society.

ProfileTakashi Shimoda
Chief Survey Officer, Center of the History of JapaneseIndustrial Technology
1963:

1996:
2002:
2005:
2006:
2009:

Graduated from the University of Tokyo Faculty of Engineering,
Department of Industrial Chemistry
Started working for Onoda Cement Co., Ltd. assigned to the Central
Research Laboratory
Later assigned to other departments, including a cement production plant,
the head office production department and a concrete subsidiary in the
U.S.
Company name changed through mergers from Onoda Cement Co., Ltd.
to Chichibu Onoda Co., Ltd. (1994), then to Taiheiyo Cement Co., Ltd.
(1998)
Appointed as the general manager of the Chichibu Onoda Central
Research Laboratory
Appointed as managing director of Taiheiyo Cement, overseeing theLaboratory, Construction Materials Business Department and Ceramics
Business Department
Appointed as an outside company auditor for Central Glass Co., Ltd.
Retired from Taiheiyo Cement as director and managing executive officer
Retired from Central Glass as outside company auditor

Contents

1 Introduction...................................................................... 2
2 The History of Cement/Concrete: The Origin of the Modern
Cement Industry .............................................................. 6
3 Cement Manufacturing Technology in Japan in the Meiji
and Taisho Periods ........................................................ 13
4 From the Early Showa Period and the Pacific War to the
Post-War Reconstruction Period (1926-1960) ................ 23
5 The Development of Japanese Cement Manufacturing
Technology (1960- ) 1) 2) 3) 4)............................................ 45
6 Environmental Conservation Technology and Measuresagainst Global Warming ................................................. 65
7 Advances in Cement Chemistry ..................................... 70
8 Trends in Cement Standards and the History of the
Cement Types and Blended Cements ............................ 85
9 Evolving to a Contributing Industry for the Sustainable
Resource-Recycling Society .......................................... 95
10 Summary: Systematization of Cement Manufacturing
Technology .................................................................. 105
11 Conclusion and Acknowledgements ............................. 108
Appended figure: Systematization Diagram of Cement
Manufacturing Technology in Japan.................................. 109
Appended tables: Cement Manufacturing Technology
Historical Resources Confirmed Location.......................... 110
Chronology of Cement Manufacturing Technology ............ 111

1

Introduction

The cement industry in Japan today is world-class inall aspects, from the high quality of the cement products
to the industry’s energy conservation technology, laborproductivity and technologies for utilizing industrial
waste and byproducts as alternative fuel and raw
materials (AFR). Since the 1990s, the Japanese cement
industry has added another layer of purpose over andabove its existing role as “an industry providing basic
construction materials”, with the mission to become “acore industry in a resource-recycling (sustainable)
society”. This systematization survey report on cement
technology discusses the development of cement
manufacturing technology from its introduction to Japanin the early Meiji Period (1870s) through to the presentday, with particular focus on “energy-saving technology”,“quality control technology” and “resource recycling
technology”.
Most cement companies around the world concentrateon “cost-effective production of high-quality cement
through the skilled use of cement manufacturing
equipment purchased from plant manufacturers”. By
contrast, Japan’s main cement companies have not limited
the aim of their technology development to simply“improving operation of cement manufacturing
equipment”. They have become deeply involved in“technologies related to cement utilization”, such asconcrete and soil improvement, and even as far as“developing cement manufacturing equipment”. Thisapproach to technology development has ultimately led toworld-standard cement manufacturing technology. This
point is also noted in this paper.
In terms of technological content, the aim has been toprovide an initial reference guide for researchers,
engineers, technicians and students who learn more aboutcement manufacturing technology, the types and qualities
of cement and the history of its development.

1.1 Cement and Concrete 1)“Cement” is a fine gray powder that has a characteristic
property of hardening when mixed with water(hydraulic-setting). Cement is one of the materials used tomake “concrete”. Almost all cement produced is used formaking concrete. In other words, cement only serves auseful role in the form of concrete.
The main raw materials in “cement” are limestone andclay. To produce 1 ton of cement requires around 1.2 tonsof limestone and around 0.3 tons of clay. The materials
are dried and ground, then burned in a rotary kiln at
1450-1500ºC to produce clinker. The main constituent

mineral contained in clinker is calcium silicate, alongwith calcium aluminate and calcium aluminoferrite.
These minerals have characteristic properties of forming
hydrates and hardening when reacted with water(hydraulic-setting). The fine powder product produced bygrinding clinker mixed with around 3% gypsum is cement(Portland cement).
“Concrete” is made up of cement, waters, fineaggregate (sand), coarse aggregate (gravel) andadmixtures (see Note 1) (Figure 1.1). In terms of the
proportion of these constituents within concrete, thehighest proportion is taken up by coarse aggregate,
followed by fine aggregate, water, cement and admixture.
Concrete has become an indispensable construction
material used in the construction of buildings, bridges,
roads, waterways, tunnels, dams, harbors, airports andvarious other structures essential to life in society.

Coarse aggregate

Fine aggregate
Water
Cement(1) Cross-section of hardened concrete
CementCement paste

MortarConcrete

CementCement Water

Water

Water

Fine aggregate (sand)Aggregate
Fine aggregate (sand)Coarse aggregate (gravel)

Note: Proportions are approximate by relative weight(2) Concrete mix design(Note) In addition to the above, in many cases admixtures are
mixed in to improve the quality or workability of the concrete(see Note 1).

Fig. 1.1 Composition of Concrete 1)

Beside concrete, applications for cement include use as
cement paste, mortar and soil stabilizer. Cement paste is a
mixture of cement and water, while mortar is a mixture of
cement paste and sand (fine aggregate) (Figure 1.1 (2)).
Cement paste is used in materials such as grout (see Note2). Mortar is widely used as an outer wall coating on
wooden buildings and as a joint-filling compound forbricks and concrete blocks. Soil stabilizers are used inapplications such as improving soft ground; various
technologies are being developed for the use of cement asa soil stabilizer.

History of Cement Manufacturing Technology21.2 The Japanese Cement Industry

1)

The cement industry in Japan began in 1875 with thefirst domestic production of cement. It has undergone
constant technological development, expanding andenlarging as the Japanese economy boomed, to become
world-class in cement quality and all aspects ofmanufacturing technology, as mentioned in the
introduction.
In terms of scale of production, as at April 2012 there
are 17 companies and 30 plants in the industry, with aclinker production capacity of 54.76 million tons. In
terms of scale of enterprise, there are seven large
companies with capital stock worth over ¥10 billion andten medium-sized companies with capital stock worth
under ¥10 billion. Eleven of the 17 companies are
specialized companies dealing mainly in cement
manufacturing, while the remaining six companies areengaged in multiple types of business, such as in thechemicals industry.
1.2.1
Domestic Cement Plants 1)
Figure 1.2 shows a typical cement plant. As mentioned
above, Japan has 30 domestic cement plants. Many ofthese are located in areas rich in limestone, one of theprincipal raw materials, such as the Kitakyushu area (fourplants) and Yamaguchi Prefecture (four plants), or in the
Kanto area (six plants), which is Japan’s highest area of
cement consumption. Typical of process industries,
cement plants have an average annual production capacityof around 1.8 million tons, although there are also somelarger plants capable of producing over 6 million tons per
year. With plants becoming increasingly mechanized andcomputerized, the average number of full-time employees
at a plant is down to around 100 people. The largest
cement plant in Japan occupies 680,000m2.

Fig. 1.2 Bird’s-Eye View of a Cement Plant 2)

1.2.2
The Cement Manufacturing Process 1)
Figure 1.3 shows an overview of the cement
manufacturing process. The raw materials for cement are
limestone and clay (see Table 7.1 for details). The “raw3materials process” involves proportioning, drying,crushing and grinding the raw materials. During the“burning process”, the raw materials are burned at
1450-1500ºC. The facilities used for this are the largest
and grandest at the plant, with the preheater tower
stretching up 80 m in height and the rotary kiln measuring
5-6 m in diameter and 100 m in length (Figure 1.4). The
fuel used for burning cement (mostly coal) is fired fromthe burner into the calcining furnace and the rotary kiln
during the “burning process” shown in Figure 1.3. Clinker
produced from the rotary kiln is transported into the“finishing process”, where it is mixed with gypsum andground. The finished cement product is then stored insilos for the “shipping process”. Most of the cement isshipped from cement plants as powder (bulk cement).
“Bagged cement” packed in paper sacks accounts foraround 3% of shipments. Bulk cement is transported bytanker ships, railroad freight cars and trucks.
1.2.3
Cement Production Volume 1) 3)
The domestic cement production volume reached apeak in 1979 at 87.94 million tons. Although this wasfollowed by a downward trend in keeping with sluggish
economic growth, some recovery was seen from 1987. In
1996 there was a late-minute rush in demand before theraising of the consumption tax rate, coupled with highrebuild demand following the Great Hanshin Earthquake.
With the Asian export market also firm, production
volumes reached all-time record high of 99.27 million
tons. This was again followed by a downward trend, withproduction remaining steady at 70 million tons from 2001.
This plateau ended in 2008 with a further downward trend.
Production volumes for 2014 were 61.91 million tons,
including clinker for export.
Domestic Demand for Cement 1) 3) 4) (seeFigure 5.1)
Domestic demand for cement continued to growconsistently throughout the postwar reconstruction andrapid economic growth. With public investment into
fundamental infrastructure such as railways, roads,
harbors and dams, the production activity of materials
industries such as electricity, steel and coal began toincrease. Subsequent capital investment focused on
manufacturing industries such as petrochemistry,electrical appliances, machinery and automobiles. As aresult, the domestic demand for cement kept in step withthe pace of industrialization in Japan, which was catching
up to the developed countries in the West.
The growing demand for cement came to a halt withthe first oil crisis (October 1973). With repeated rises andfalls ensuing, a record peak came in 1990, towards theend of the bubble economy. Demand rose to 86.29
million tons that year, followed by a continuing
downward trend due to a prolonged recession anddropping more recently to around 40 million tons. In 2014,
domestic sales totaled 45.9 million tons.
1.2.4

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchRaw materials
process

Finishing process

Burning process

Fly ashSlag powder

Flow of gas

Electrostatic
precipitator

Flow of raw
materials

Limestone

Clinker
silo

Mixer

Gypsumyard

PortlandcementClinker

CycloneBoilerClay

NSP tower

Silica orother rawmaterial
yard

BlendedcementCementsilo

Smoke stackPre-crusher

Calciner

Blending Raw
material
silo storage silo

Coal
Finishing mill

Shipping(Flow of steam)Raw material mill

Kiln
TurbineGenerator

Bulk loading truck

Cement tanker
Bulk loading
freight car

Fig. 1.3 Cement Manufacturing Process 1)

1.2.5
Cement Exports and Imports 1) 3)Japan has continued to hold its position as a major
world exporter of cement. The reason for this lies with its
cost competitiveness due to its high number of coastal
cement plants and its capacity for bulk transportation by
ship. Exports have remained steady at around 10 million
tons in recent years (since 2010). The 9.11 million tons
produced in 2014 was approximately 15% of the domestic
production volume. Meanwhile, cement imports into
Japan have remained at a level around 600,000 to 900,000
tons. Cement is a completely liberalized commodity andJapan’s cement production and distribution costs areinternationally competitive.
Fig. 1.4 Preheater Tower and Rotary Kiln 2)

Examination of domestic cement sales (excluding
imports) by demand sector in 2014 reveals thatready-mixed concrete accounted for 72% and precast
concrete accounted for 12%, with these two areas
together accounting for 84%. Further examination of the
final consumption of cement by market sector reveals anear-even split between the public and private sectors of
51.0%:49.0%.
The domestic price of cement is around ¥10,000 per
ton (2012, ordinary Portland cement, Tokyo region),
which works out at ¥10 per kg, a surprisingly low pricefor a chemical product, making it a high performer among
commodity prices.

1.2.6

Overseas Expansion of the Japanese
Cement Industry 1)
Following the Second World War, overseas expansionof the Japanese cement industry mainly involved theestablishment of transfer stations for the purpose of
ensuring reliable export supplies. In the 1990s, overseas
expansion began in earnest with the construction of
cement plants and other major investments. The main
target area for this overseas investment was the booming
Pacific Rim. As at 2012, Japan’s overseas cement
production bases included two plants in Korea (14.76
million ton capacity), seven plants in China (8.87 million
tons), six plants in two countries in Southeast Asia (11million tons), four plants in California and Arizona, USA(4.84 million tons) and one in the Pacific (200,000 tons),
making a total of 20 plants in six countries with an annual
production capacity of around 40 million tons.

1.3 The Mission to Become a Core Industry in a
Resource-Recycling Society1) 4)History of Cement Manufacturing Technology

4With the growth of the economy, Japan has come tothrow away a lot of waste and byproducts. However,difficulties in recent years with locating new landfill sites
have raised the question of how to promote recycling andreduce the amount of landfill for society as a whole. In
this social climate, the cement industry has gone over andabove its existing role as “an industry providing basic
construction materials” and taken on the significant rolein becoming “a core industry in a resource-recycling
society” by utilizing large volumes of waste andbyproducts as fuel and sources of raw materials for
cement manufacturing, a mission that grows insignificance over time.
In detail, the cement industry has developed a broad
range of waste and byproduct recycling technologies
based on existing cement manufacturing facilities andburning technologies and now reclaims and reuses around28.5 million tons (in 2012) of more than 20 types of waste
and byproducts from other industries. Converted into
volume, this is the equivalent of approximately 21 million
m3.
While cement production has continued in a downward
trend since peaking at 99.3 million tons in 1996, theamount of waste and byproduct used in the manufacturingof 1 ton of cement is actually increasing, thanks to theefforts of the cement industry (1990: 251kg/t-FHPHQWĺ
2012: 481kg/t-cement, see Figure 9.2).

1.4 Scope of Technologies for the Purpose ofthis Systematization Survey Report on
Cement Technology

Figure 1.3. This covers the processes used by mostcement manufacturing plants.
The unchanging development goals for cement
manufacturing technology have always been energy
conservation, improved labor productivity, mass
production, sustainable supply and consistent quality. In
recent years, another goal has been added, as mentioned
above: “technology development that fulfils the missionof a core industry in a resource-recycling society”. In
other words, the development of resource-recycling
technologies at cement plants is growing in relative
importance.
Note 1: Admixtures and Additives
Admixtures and additives are ingredients added to concrete inorder to improve its workability or its quality. These are termed
according to the mixing ratio. Additives can include
blast-furnace slag, coal ash (fly ash) and limestone powder;admixtures can include air-entraining (AE) agents,
water-reducing agents, accelerating agents, hardening
accelerators, retarders and corrosion inhibitors. Various organicand inorganic chemicals have been developed as concrete
admixtures (see 2.4, 8.4).
Note 2: Grout
A general term for cement milk or cement mortar used as filler
for gaps between tunnel walls and rocks and for jointing in
concrete structures. Also used for increasing the adhesive
capacity of steel wires in pre-stressed concrete.

References (all in Japanese)
1) Japan Cement Association, Introduction to Cement &Concrete, 2013.
2) Supplied by Taiheiyo Cement Corporation.
3) Japan Cement Association website, September 2015.
4) Japan Cement Association, Cement Handbook, 2014.

This report focuses on the technologies indicated in

5

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

2

The History of Cement/Concrete: The Origin of
the Modern Cement Industry

This chapter discusses: (1) ancient “cement”; (2) theinvention of modern “Portland cement” in the United
Kingdom during the Industrial Revolution; (3) the originsof the Japanese cement industry in the early Meiji Period(1870s); and (4) the emergence of modern concrete
technology.

2.1 The History of Pre-Modern Cement andConcrete

1) 2) 3) 4)

With cement broadly defined as “inorganic bonding
material”, its origins can be traced back to the Neolithic
Period around 9,000 years ago. This is based on the
discovery of hydraulic material similar to modern
concrete in the floor and walls of a dwelling excavated at
Yiftah’El in the Galilee region of Israel. This concrete isreported as being made up of limestone-based cement andcrushed limestone aggregate mixed with a small amountof water. In China, hardened substances primarily madeup of calcium carbonate and primarily made up of caliche
containing silica, presumed to have been hardened byreaction with water, were discovered in the floor of adwelling site near Xi’an dating back around 5,000 years.
While these “cements” are said to be “hydraulic” (seeNote 1), it is not known how they were used; thetechnology was not passed down to future generations
and was lost.
Meanwhile, for the construction of the pyramids ofAncient Egypt, believed to be around 2,600 BC, thestones were joined with mixtures of limestone, plaster,sand, ash and mud, which were mixed with water and left
to air-harden. This bonding material did not harden inwater and is considered to be a different type from thehydraulic bonding materials found at Yiftah’El and Xi’an;however, it fits within the definition of “cement” as an“inorganic bonding material”.
Mortar mixed from slaked lime (Ca(OH)2) andvolcanic ash, from a site in Greece dating back to around
1,000 BC, has been confirmed to have been used as a
joint-filling compound.
Thus it appears that humankind, throughout the courseof time, came to understand by experience thatnaturally-occurring gypsum or limestone would harden
once heated and combined with water. By around 200 BC
in ancient Rome, active efforts were being made to burnnatural gypsum and limestone, with plaster of Paris(hemihydrate gypsum, CaSO4½H2O) and quicklime(CaO) being produced using “kilns”. Hemihydrate
gypsum hardens as it absorbs water and turns into

dihydrate gypsum. Quicklime reacts with water to form
calcium hydroxide (Ca(OH)2), which reacts with thecarbon dioxide in the air to form calcium carbonate(CaCO3). It hardens through this transformation(carbonization) (air-hardening, see Note 1).
Further forward in Roman times, it was known that a
mixture of quicklime and volcanic ash would (1) harden
with water and (2) not break down in water (hydraulicsetting, pozzolanic reaction, see 8.3.2). This mixture wascombined with stone and used liberally on everythingfrom roads, castle walls and watercourses through tohouses and temples.
Although these ancient cements can be defined as“cement” in that they are types of “inorganic bonding
material”, they are essentially very different from the“cement” we know today. They were produced with theidea that skillful use of mixed materials would produce astrong bonding material, rather than the idea of
proportioning, burning and chemically reacting raw
materials, distinctive of modern cement. The quality ofthis “ancient cement” would not be sufficient for the“concrete structures” of today.
Little progress was seen in the history of cement foraround 2,000 years, through the Middle Ages to the early
18th century. Consequently, the medieval structures still
standing in Europe today are about the same as thosefrom ancient Roman times in terms of materials andconstruction method, with no fundamental changes
discernable.

2.2 The Invention of Modern Cement 1) 2) 3) 5)
The Industrial Revolution began in the United
Kingdom around the mid-18th century. As part of thatwave, there was a succession of research discoveries andinventions that led to the invention of modern cement.
In 1756, John Smeaton (UK) was contracted with therebuilding of England’s Eddystone Lighthouse (Figure2.1). The joint-filling compound between the stones at thebase of the lighthouse, constantly washed with seawater,
had to be far more water-resistant than theconventionally-used mortar made from slaked lime. After
researching the burning of various different kinds oflimestone, he found that mortar using a slaked limestone
with the impurities of clay produces better results thanpure slaked limestone mortar in terms of hardening inwater and offering superior resistance. (see Note 2). In his
published findings, he referred to it as “hydraulic mortar”.

History of Cement Manufacturing Technology

6

Until then, the idea noted by Marcus Porcius Cato(234-149 BC) of Rome that “to produce good mortar,
only high-purity limestone should be used, containing noclay or other impurities” had been taken literally. With his
experiment research, Smeaton disproved the “accepted
practice”.
While Smeaton wrote that he “did not doubt but tomake a cement that would equal the best merchantable
Portland Stone in solidity and durability”, he did not file apatent for the material or the name.
In 1796, 40 years after Smeaton, James Parker (UK)burned clay-containing limestone in a limekiln at around
1100ºC 3) and ground it to produce a hydraulic cement.
Later known as “Roman cement”, this cement was widelyused on projects, including the Thames Tunnel.
Improvements were made to it in the 1810s by James
Frost (UK) and Louis Joseph Vicat (France).
Independently, they proved that a ground and blended
mixture of limestone and clay produced a similar result toclay-containing limestone (marl). This led to the modern
cement manufacturing method.

inventor of Portland cement. See 7.4.1 for more details on
this.
The initial burning temperature for Portland cement
according to the Aspdin patent is assumed to be around
1200ºC 3). The quicklime and clay would have reacted
together to produce small amounts of belite (2CaO·SiO2
solid solution), interstitial material and other cement
minerals, as well as large amounts of quicklime. It would
have been little different in quality from Roman cement.
However, Aspdin’s invention triggered rapid research
progress on Portland cement.

Fig. 2.2 A Shaft Kiln built by Aspdin 1)

Fig. 2.1 The Eddystone Lighthouse built by John Smeaton
1)

An English mason, Joseph Aspdin, invented a methodof producing cement by mixing quicklime made fromcrushed and burnt limestone with clay in a certain
proportion. Water was added to the mixture before finely
grinding it, drying it and re-burning it in a shaft kiln (seeFigure 2.2). In October 1824, Aspdin patented his
invention under the title of “An Improvement in the Modeof Producing an Artificial Stone” and named the product“Portland cement” (see Note 3). Thus, Aspdin became
known as the “inventor of modern cement”, although
Smeaton, Vicat and other forerunners made significant
achievements (see 7.4).
Aspdin’s patent lacked two important points in termsof the modern definition of Portland cement: there is norange given for the ratios of limestone and clay and there
is no description given of burning the mixed raw
materials until semi-molten. Consequently, objections
were later submitted on the naming of Aspdin as the7

Isaac Charles Johnson (1811-1912), a technician at
Roman cement manufacturer, JB White (UK), wasgranted permission from his company to start
manufacturing the new Portland cement developed by
Aspdin. In 1884, based on independent experiments andresearch, he found that the basic conditions for producing
a uniform product are: (1) the ratio of limestone and clay
to produce high quality cement; (2) burning the raw
materials until semi-molten; and (3) the homogeneity
achieved by the proper mixing of raw materials. Thesefindings established the basic principles for modern
Portland cement manufacturing.
Johnson’s conditions for manufacturing Portland
cement made it possible to achieve significant
improvements in quality by “burning the mix of limestone
and clay at high temperatures of 1250ºC or above untilsemi-molten”. This led to the adding of alite (3CaO·SiO2
solid solution) to the Aspdin-era cement minerals of belite
and interstitial material 3). (Note: Alite, belite andinterstitial material are discussed in more detail in
Chapter 7.)
Portland cement was thus developed in the United
Kingdom, with four manufacturing plants starting
operation in 1850. The superiority of the product wasdemonstrated at the Great Exposition in 1851 in London,
after which it came to be produced at an industrial scalein countries all around the world in place of Roman
cement. Portland cement started being manufactured in
the United Kingdom in 1825, in France in 1848, in

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchGermany in 1850, in the United States in 1871 and inJapan in 1875.

2.3 The Originsof the Japanese Cement Industryth1) 2) 3) 6) 7) 8) 9) 10) 11) 12)(late 19 century)

2.3.1

The Beginning of Government-Managed
Cement Plants
Japan imported Portland cement and put it to use inconstruction work in 1861. It is first believed to havebeen used to join the bricks in the construction of theNagasaki Iron Works, built by the Japanese shogunate
under the guidance of Dutch naval officer Henrik Hardes.
After that, Japan used small volumes of imported cementin projects such as the Yokosuka Iron Works, started in
1866 by the shogunate and taken over by the Meiji
Government (completed 1872, renamed Yokosuka
Shipyards), the Nojimazaki Lighthouse (completed 1896)
DQGWKH-ǀJDVKLPD/LJKWKRXVH(completed 1870). The
price of imported cement at the time was ¥50-60 per ton(¥8.50 per 180kg barrel; ¥7.50 per 135kg barrel). Basedon the price of rice at the time compared to today,
imported cement at the time is estimated to have costaround ¥500,000 per ton in today’s currency 11). (Theprice of ordinary Portland cement in 2013 was around¥10,000 per ton.)
In 1871, during the construction of the No. 2 Dock at
Yokosuka Shipyards, the Ministry of Industry’s head of
shipbuilding Michiyoshi Hiraoka (Figure 2.3), who was
overseeing the construction of the dock, noted that
cement was by far the most expensive material used inharbor construction and other construction work. Sensing
a pressing need for domestic production, he proposed to
the Vice-Minister of ,QGXVWU\3ULQFH+LUREXPL,WǀWR
start a government-run cement manufacturing enterprise.

Fig. 2.3 Michiyoshi Hiraoka 1)

In February 1872, a fire broke out in Ginza, burning
WKURXJKWKHHQWLUH.\ǀEDVKLGLVWULFWDQGGHVWUR\LQJWKH
Ministry of Industry’s buildings in Tsukiji, the Tsukiji
Honganji Temple and a number of hotels in Tsukiji. The
government decided to rebuild the Ginza district withbrick in order to protect it from fire. Plans for theconstruction of the brick Ginza district were undertakenby overseas contractor Thomas James Waters (UK),overseen by the Department of Construction under the
Ministry of the Finance’s Bureau of Civil Engineering.

Intending Japan to supply its own bricks and cement,
Waters oversaw the construction of a Cement Works on
the site of the Sendai Estate in Kiyosumi in the suburban
Tokyo district of Fukagawa (Figure 2.4). Construction
began in July 1872, with cement production commencing
by the end of 1873. The manufacturing method is notknown in detail, but based on the IDFWWKDW6DEXUǀ
Utsunomiya “succeeded in modifying it to a wet method”,
as shall be mentioned later, it is presumed to have been adry or semi-dry process (see Figure 3.2 for details on dry
and semi-dry processes). In any case, the facilities wereless than perfect and the quality of the manufactured
cement was inferior to its imported counterpart.

Fig. 2.4 Government-Managed Cement Works(Fukagawa, Tokyo) 7)

Meanwhile, the Ministry of Industry also embarked on
research on cement manufacturing, having received the
proposal by Michiyoshi Hiraoka, mentioned previously.
+LUDRNDLQYLWHG6DEXUǀ8WVXQRPL\D )LJXUH
1834-1902), who had spent time in the West studying
modern industry from May 1872 to September 1873, tojoin his team at a chemicals laboratory in Akasaka, Tokyo
to conduct research on cement manufacturing.

Fig. 2.5 6DEXUǀ8WVXQRPL\D1)

The Cement Works in Fukagawa came under thejurisdiction of the Home Ministry in November 1873 andwas then transferred to the Ministry of Industry’s Bureauof Manufacturing in January the following year. For the
first time, the cement manufacturing operations of the
Ministry of the Treasury and the Ministry of Industry
were merged under the Ministry of Industry, under the
RYHUVLJKWRI6DEXUǀ8WVXQRPL\DHistory of Cement Manufacturing Technology

8Utsunomiya had conducted repeated experiments at the
Fukagawa plant, but had not obtained a satisfactory
quality of cement. He then decided to fundamentally alter
the method of manufacture to incorporate the new “wetprocess” (see Figure 2.6) used by the British and theFrench. He completely demolished the facilities at the
government-managed plant at Fukagawa and brought in
new facilities. The plant was completed in 1875 and on
May 19, a small quantity of cement was produced – thefirst Japanese cement that could rival the quality ofoverseas products. The day has later been celebrated as“Cement Commemoration Day”, with cement technology
conventions and other events being held.
(Note) :KLOH6DEXUǀ8WVXQRPL\DLVUHFRUGHGDVKDYLQJsuccessfully manufactured Portland cement using
a dry-process shaft kiln on May 19, 1875,
according to Takashi Ueno’s Supplement to theHistory of Cement Technology 12), it was reported
that cement had been manufactured and sold under
the oversight of Thomas Waters using a
dry-process shaft kiln that had started operating in
1873. A detailed discussion of the historicalsources regarding this is provided in Ueno’s work,
pp. 5-7.
Having succeeded in manufacturing cement,
Utsunomiya traveled back to the United States and theUnited Kingdom in 1875 and 1876 for further study. On
his return to Japan, he immediately set about improving
and augmenting his plant facilities, resulting in steadyincreases in production volumes from the late 1870s
onwards. Government-initiated economic and industrial
modernization was advancing rapidly at this time and aflurry of construction meant a growing demand for
cement for railroads, harbors, military facilities,
government buildings, universities and factories.
The production facilities at the government-managed
Fukagawa plant under Utsunomiya were as follows.
Two cement kilns (shaft kilns, 14.5m high, 1.2m upper
diameter, 3.6m central diameter), one drying area, one
powder area, two settling basins and one agitating basin.
Figure 2.6 shows the wet process method employed by
Utsunomiya using these facilities.
Slaked lime and local Fukagawa river mud were mixed
at a fixed ratio in a basin called an agitating basin, wherewater was added. After being agitated and coarse particles
and other debris had been removed, the mix was thentransferred to the settling basin to settle. Once settled, theupper water was removed, leaving a thick slurry to betaken out and dried. The agglomerated mix of slaked lime

and clay was then loaded with coal into a brick shaft kiln
called a bottle kiln and burned to produce clinker. The
clinker was taken from the shaft kiln, ground andweathered (see Note 4) for around three months in aweathering storehouse to produce the finished cement
product. However, while this method did not require theraw materials to be ground, it did require large amountsof water; processing was also labor-intensive and took along time, as the settling and drying processes had to be
included. To begin with, there was no crushing or
grinding machinery able crush and grind the hard
limestone and it is thought that a method of hydrating
pre-burnt limestone was used to extract the necessary fine
lime component.
2.3.2

Mastering of the Technology by Japanese
without Relying on Overseas Contractors
Many Japanese industries in the Meiji Period startedout by inviting engineers, known as overseas contractors,
to provide guidance and instruction on everything frombuilding facilities to operating technology. However, it isworth noting that the cement industry did not use
overseas contractors, but started out by mastering
Western technology through diligence and hard work.
Thomas Waters, who had been contracted for theconstruction of Ginza’s brick precinct and oversaw theconstruction of the first Cement Works in Fukagawa toprovide the necessary cement, was an architectural
engineer and had no experience with cement
manufacturing. Consequently, the cement produced in thefirst plant built under his oversight was poor in quality. It
ZDV6DEXUǀ8WVXQRPL\DKDYLQJSHUVRQDOO\VWXGLHGLQWKH
West, who put his experience and creative originality towork to completely rebuild the Fukagawa plant andfinally produce marketable cement.
For a more detailed account on Michiyoshi Hiraoka
DQG6DEXUǀ8WVXQRPL\DWKHIRXQGHUVRIWKH-DSDQHVH
FHPHQWLQGXVWU\DVZHOODV-XQSDFKL.DVDLDQG6ǀLFKLUǀ
Asano (see following sections), who built cement
PDQXIDFWXULQJLQWRDQLQGXVWU\UHIHUWR6XWH]ǀ
Sugishita’s Japanese Cement (Poplar, 1962) 13).
2.3.3
Development as a Private Industry
Japan’s first privately-managed cement plant wasconstructed in 1881, in what is now the city of
Sanyo-Onoda in Yamaguchi Prefecture. Operationscommenced in 1883. This was the founding of what later
became the Onoda Cement Company.

Raw material process

Water

Limestone

Limekiln

Weatheringarea
or hydration

Coal
Agitatingbasin

Settlingbasin

Dryingarea

Bottle kiln

Grinding

Weathering
storehouse

Riverbed mud

Fig. 2.6 Shaft Kiln / Wet Process Cement Manufacturing Process 7)

9National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

PackingAt the center of this promotion of enterprise was
Junpachi Kasai (Figure 2.7, 1835-1919), a former feudal
UHWDLQHURIWKH&KǀVKǌ'RPDLQ.DVDLLVVDLGWRKDYHVHHQ
cement being used in the construction of storehouses in
his home area in Yamaguchi in 1875 and developed akeen interest in how a powder mixed with water could
harden and firmly bind to stone. He is said to have later
learned about cement manufacturing technology at thesole government-managed plant by speaking with
Michiyoshi Hiraoka when Hiraoka returned to
Yamaguchi in 1879 and started thinking about
HVWDEOLVKLQJDFHPHQWEXVLQHVV³WRDLGWKH&KǀVKǌ
Domain retainers who had lost their income when the
feudal system was abolished”.

Fig. 2.9 The Onoda Cement Plant (around 1890) 7)

In 1884, the government-managed Cement Works in)XNDJDZDZDVVROGRIIWR6ǀLFKLUǀ$VDQR )LJXUH
1848-1931), an industrialist and merchant who had
supplied the factory with coal, and was further developed
to become Asano Cement.

Fig. 2.7 Junpachi Kasai 14)

The following year, Kasai and his friend Sahee
Arakawa decided to travel to Tokyo with local
Yamaguchi marble and mud and to start a cement
EXVLQHVVZLWKJXLGDQFHIURP6DEXUǀ8WVXQRPL\DDWWKH
Fukagawa Works Sub-Bureau (formerly the Cement
Works). The reasons Kasai chose the Onoda site were that
it was near to sources of the main fuel and raw materialsof coal, limestone and mud and that it faced the sea forease of product transportation, as well as the fact that thearea was newly-reclaimed land and the rent was cheap.
Figure 2.8 shows the bottle kiln at the Onoda Cement
plant constructed in 1883 (still standing, designated as an
Important Cultural Property). Figure 2.9 shows apanoramic view of the same plant, taken around 1890.

Fig. 2.8 Shaft Kiln (Bottle Kiln) Still Standing at the
Taiheiyo Cement Corporation Onoda Plant 7)

Fig. 2.10 6ǀLFKLUǀ$VDQR9)With the creation of these two companies, the Japanese
cement industry developed into the privately-managed
industry it is today. Onoda Cement and Asano Cement(which changed its name to Nihon Cement after theSecond World War) merged with a third company,
Chichibu Cement, in the 1990s to form the present-day
Taiheiyo Cement, which remains a core enterprise in the
cement industry today.
Although private cement production had begun under
the circumstances as outlined, government financial
difficulties and a general lack of awareness about cement
meant that demand did not grow as expected. Initial
production volumes were reportedly around 25 tons permonth (EDUUHOVĺVHHQRWHEHORZ IRUWKH
Fukagawa and Onoda plants combined. However, the*UHDW1ǀEL(DUWKTXDNHRIGHPRQVWUDWHGWKH
earthquake resistance of concrete structures, while
Japan’s victory in the First Sino-Japanese War(1894-1895) and the Russo-Japanese War (1904-1905)
saw an increase in demand for cement and a significant
increase in production volumes. By 1897, the number of
cement companies has grown to 15, while a new rotary

History of Cement Manufacturing Technology

10kiln (Figure 3.5) was imported from the United States in1903 to replace the conventional shaft kiln for burning the
raw materials, bringing about a dramatic rise in productquality and production volumes. The advances inJapanese cement manufacturing technology from the late
1880s onwards are discussed in more detail in Chapter 3.
(Note) Meiji-era cement transportation was done inbarrels (see 4.12.1). One barrel weighed 400lb,
approximately 181kg, when the Onoda and Asano plants
were being established (1883). Figure 2.11 shows (1) acement barrel and (2) the filling of barrels on site.

(1) Cement Barrel 1)

concrete era”.
To further increase the tensile strength of concrete, P.
H. Jackson (USA) began researching pre-stressed
concrete in 1886. This involved inserting steel into theconcrete and tensioning it at both ends, thus creatingconcrete that was strong yet elastic. This technique waslater improved upon by researchers from many different
countries, with Eugene Freycinet (France) theorizing on
the relationship between the concrete and the reinforcing
material and applying it to many concrete products andstructures, thus laying the groundwork in concrete
technology.
Reinforced concrete technology is thought to have been
introduced to Japan around 1895. The oldest civilengineering structure built using this method is a bridge(Figure 2.12, 7.3m long) over the Lake Biwa Canal in
Kyoto, built in 1903, and it is still standing. The oldest
building structure is believed to be a pump house at
Sasebo Heavy Industries in Nagasaki, built in 1904.

(2) Filling Cement Barrels 15)

Fig. 2.11 Meiji-Era Cement Barrel for Transportation

2.4 The Emergence of Concrete Technology 1)
While concrete technology lies beyond the scope of
this survey report, cement is used as a constituent material
in almost all concrete. In other words, cement only servesa useful role in the form of concrete. Consequently, thedevelopment of concrete technology beyond the inventionof modern cement is briefly discussed here.
Portland cement, invented by Aspdin and improved by
Johnson, is superior in quality to Roman cement and has
expanded in application from a jointing material (mortar)
between stones to being used in structures made entirely
from concrete. However, with concrete on its own being
found to be weak (brittle) in the tensile direction (lacking
tensile strength), research began in France in the 1850s tocompensate for this weakness.
In 1867, gardener Joseph Monier (France) successfully
created a thin yet strong flowerpot by inserting wire mesh
into mortar. The wire compensated for the weakness ofthe mortar, thus creating reinforced concrete, which
would have a major impact on later structures. Monier
later put this to use in pipes, water tanks and concreteslabs, going as far as to construct a 15.6m long, 4.2m
wide reinforced concrete bridge in 1875.
This prompted the use of reinforced concrete inbuildings, bridges, tunnels, dams and other structures in
Europe until around 1900, ushering in the “reinforced

11

Fig. 2.12 Japan’s Oldest Remaining Concrete Bridge over
the Lake Biwa Canal 1)

Pre-stressed concrete was introduced to Japan in 1939
and used for railroad sleepers around 1949 and for aplatform at Tokyo Station in 1951.
The invention of reinforced concrete and pre-stressed
concrete, combined with improved cement quality, could
be called the driving force behind making later concrete
structures “taller, longer, wider, deeper, stronger andlighter”.
Concrete admixtures have also contributed to
improving the workability and performance of concrete inrecent years. Admixtures were introduced to Japan in thelate 1940s following the invention and practicalimplementation of air-entraining (AE) agents in the
United States in the 1930s. These began to be used to
improve workability (handling prior to hardening),
bleeding (water rising to the surface after pouring) andfrost resistance. Later, with construction using concrete
pumps becoming more widespread, successive AE
water-reducing agents with both air-entraining andNational Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchwater-reducing effects emerged up until the 1990s, alongwith fluidizing agents and improved high-performance
AE water-reducing agents. These have enabled the recent
production of an ultra-high-strength concrete with acompressive strength of over 100 N/mm2, thus further
expanding the possibilities for concrete high-risebuildings.
Other admixtures have also emerged to give concrete a
range of different characteristics, including expansion
agents, underwater-hardening concrete and other specialty
admixtures. These have become an indispensable material
for the future development of concrete technology. (SeeNotes 2, 3 and 4 of Chapter 8.)
Note 1: Air-Hardening and Water-Hardening
Water-hardening or hydraulic refers to the property ofhardening when reacted with water, while air-hardening refers
to the property of hardening when reacted with air (mainly
carbon dioxide gas).
Note 2: Clay-Containing Limestone
While most of the limestone found in Japan is hard with highpurity of calcium carbonate (CaCO3), in Europe and the UnitedStates, there are other types of limestone, such as soft limestone(chalk) and marl, which contains quite a high clay fraction.
Marl is sometimes also called cement rock, as it can be heated
to produce a water-hardening material. Roman cement was
manufactured using large amounts of this marl. It can still be
used today as a raw material for cement by adjusting a few
ingredients.
Chalk is easy to crush and was a particularly useful raw
material to prepare in early cement manufacture, when proper
crushing machinery had not yet been developed.
Note 3: The Origin of the Name of Portland Cement
Aspdin named this cement Portland cement because the colorand hardness of the hardened cement resembled the Portlandstone quarried from the Isle of Portland and widely used as abuilding material in the United Kingdom at the time.
Note 4: Weathering
Weathering refers to the process of spreading cement out on afloor and allowing it to absorb the carbon dioxide in the air inorder to carbonize and inactivate the free lime (see Note 4, p.
23) in the cement powder.

References (all in Japanese)
1) Japan Cement Association, Introduction to Cement &Concrete, pp. 64-67, 2013.
2) Mitsuzo Fujii, “Development History of Portland
Cement (1)-(18)”, Cement & Concrete, No. 105-130,
1955-1957.
3) Hiroshi Uchikawa, “Social History of Cement
Material Technology (1)”, Material Technology, Vol.
12, No. 9, pp. 23-28, 1994.
4) Mitsutaka Hayakawa, “Ancient Cement andConcrete”, Concrete Journal, Vol. 40, No. 9, pp. 8-10,
2002.
5) Toyoharu Nawa, “Industrialization of Modern
Portland Cement”, Concrete Journal, Vol. 40, No. 9,
pp. 11-16, 2002.
6) Tomikazu Dainobu, Trends in Cement Manufacturing
Technology in the Meiji and Taisho Periods,
Yamaguchi University doctoral dissertation, 2007.
7) Tomikazu Dainobu, “Trends in Cement
Manufacturing Technology in the Meiji and Taisho
Periods”, CEM’s (Taiheiyo Cement Technical
Information), No. 37, pp. 2-5, 2008.
8) Onoda Cement Co., Ltd., 100-Year History of Onoda
Cement, 1981.
9) Nihon Cement Co., Ltd., 100-Year History of Nihon
Cement, 1983.
10) Taiheiyo Cement website, “Birth story”, September
2015.
11) Hiroaki Matsusato, “Industrialization of Modern
Portland Cement”, Concrete Journal, Vol. 40, No. 9,
pp. 73-77, 2002.
12) Takashi Ueno, Supplement to the History of Cement
Technology, Onoda Cement, 1980.
13) Sutezo Sugishita, Cement Industry in Japan, Poplar
Publishing, 1962.
14) Onoda Cement Manufacturing Co., Ltd., 50-Year
History of Establishment, 1931.
15) Supplied by Taiheiyo Cement Corporation.

History of Cement Manufacturing Technology

12

3

Cement Manufacturing Technology in Japan in
the Meiji and Taisho Periods

The previous chapter discussed the efforts by Hiraoka,
Utsunomiya and others that enabled the Japanese to
manufacture their own cement and the consequentestablishment of cement as an industry through the effortsof Kasai, Asano and others. In the late 1880s and early
1890s, the demand for cement grew as other industries
began to flourish. Cement companies were establishedaround the country, forming the foundations of Japan’s
cement industry.
This chapter discusses the development of cement
manufacturing technology from the late 1880s to the late
1920s. There were three major innovative technologies incement manufacturing during this time, all of which
involved bringing in technology or equipment from theWest.
(1) Transition from shaft kilns to rotary kilns in theburning process. The main kilns used in the Meiji
Period were shaft kilns (bottle kilns); the use ofrotary kilns spread rapidly in the Taisho Period.
(2) The addition of gypsum as a cement setting andhardening regulator in the finishing process. In the
Meiji Period, setting was regulated by weathering;
the addition of gypsum spread rapidly in the
Taisho Period.
(3) Cement standards were established (Japan’s firstindustrial standards).

3.1 Cement 1)Productionin the Meiji and Taisho
2) 3)
Periods

Cement production in Japan began in the early Meiji
Period, with production volumes later increasing as Japangrew in its national capabilities. Figure 3.1 shows thedomestic cement production volumes and export/importquantities during this time.

First World War

3.2 Manufacturing Technology in the Shaft1)Kiln
2) 4)
Era (late Meiji Period to around 1920)

1924

5) 6)

1921

1918

1915

1912

Russo-Japanese War

1909

1906

1903

1900

1897

1894

1891

1888

1885

1882

1879

1876

1873

1870

First Sino-JapaneseWar

Cement Production Volumes and Export/Import Quantities(tons/year)

Production
volumeImportquantity
ExportquantityYear

Fig. 3.1 Transitions in Domestic Cement Production
Volumes and Export/Import Quantities during the
Meiji and Taisho Periods 1) (logarithmic vertical
axis)

13

As illustrated above, imports far exceeded domestic
production up until around 1881; cement from thegovernment-managed Fukagawa cement plant could only
partially meet the domestic demand. Later, although
domestic production grew to around 20,000 tons byaround 1888, imports were about the same, covering onlyaround half of the domestic demand.
However, from 1889 onwards, an increase in thenumber of Japanese cement companies saw production
volumes rise to around 100,000 tons by 1893, five times
higher in five years compared to 1888; by the end of the
Meiji Period, production volumes had soared to around
600,000 tons, 30 times higher in 23 years compared to1888. As a result, import quantities dropped by several
thousand tons to as little as 1% of domestic production
volumes. However, this was also a time in which having
too many cement companies meant the increased supply
outweighed the demand. The First Sino-Japanese War
saw some export trends emerging in order to develop andretain new markets, but this only accounted for around
10% of domestic production.
The overcrowding of companies resulted in an industry
with unstable trade conditions for individual companies
and ever-changing company fortunes. As many as 51
cement companies were founded in the Meiji and Taisho
Periods, but only 18 of them survived until the end of the
Taisho Period.
The reason for the whirlwind rise and fall of thesecement companies is due to the following factors:(1) The raw materials could be procured easily inJapan, with deposits of limestone, the principal
raw material in cement, everywhere throughout thecountry and domestically-produced coal for fuel.
(2) Cement manufacturing facilities at the time wererelatively simple and could be constructed easily.
(3) Since the properties of cement meant it could not
be stored long-term, dumping was prevalent attimes of downturn or overproduction, making it
susceptible to extreme price drops.
As a result, there were many cases of companies goingbankrupt several years after constructing a plant.

Cement manufacturing began in Japan atgovernment-managed cement plants and throughout
almost the entire Meiji Period it was manufactured using
shaft kilns. This section discusses shaft kiln cement
manufacturing technology up until rotary kilns were
imported from overseas at the end of the Meiji Period.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March3.2.1

Shaft Kiln Raw Materials Processing: From
Wet Process to Dry Process with theDevelopment of Crushing and Grinding
Machinery
Since the chemical reaction through cement burning isa solid-phase reaction, the following points are very
important:(1) The mix proportion between the limestone andclay has to be properly controlled to keep thechemical composition of the cement as constant as
possible (chemical composition).
(2) The raw powder has to be as fine as possible(fineness).
(3) The limestone and clay particles have to be
distributed as evenly as possible (homogeneity).
With the early cement industry in the latter half of the
Meiji Period not yet having developed proper crushingmachinery or other mechanical devices, industry pioneers
came up with various ways of improving factors (1)-(3)above, even by the slightest amount.
6DEXUǀ8WVXQRPL\DWRRNRYHUWKH-DSDQ¶VILUVW
government-managed cement plant, constructed in 1873,
and completely rebuilt the existing facilities. Using a
manufacturing method known as the wet process, shownin Figure 2.6, Utsunomiya successfully manufactured
Japan’s first Portland cement of reliable quality in 1875
(see 2.3.1). The main reason for using the wet process atthat time was that no crushing or grinding machinery had
been developed that could prepare the limestone properly.
Accordingly, the lime material was granulated with much
effort by calcining the limestone to produce quicklime
and then hydrating the quicklime to produce slaked lime.
As the early Meiji cement plants started by copying thegovernment-managed cement plant in Fukagawa, Tokyo,
they all adopted the wet process. However, since the wet
process was not very economical or productive, they
eventually shifted to using the dry process. The dry
process was first used by Onoda Cement in 1888, having
imported a set of machinery from Germany, andgradually spread to other companies. Using a shaft kiln as
shown at the top of Figure 3.2, the dry process involves
drying the clay and feeding it together with the limestone

through three machines in sequence – a primary crusher, asecondary crusher and a mill (see Note 1) – to produce a
powder, adding water and mixing it in a blending
machine, and then transporting the blended material into a
cutter and cutting it into brick-sized pieces, which areburned in the shaft kiln after drying. Using a rotary kiln as
discussed in 3.3, the dry process requires no shaping of
the raw materials, which are burned in the kiln directly
after grinding and mixing, as shown at the bottom of
Figure 3.2.
As is evident when comparing the dry process inFigure 3.2 and the wet process in Figure 2.6, the dry
process includes the process of grinding the raw materials.
As mentioned previously, in the shaft kiln era, the wet
process was the alternative used as there was not yet any
machinery that could crush and grind the hard limestone.
The development of grinding machinery made it possible
to transition from the wet process to the dry process.
There were three types of dry process: the common“pure dry process” using limestone, the “semi-dry process”
using slaked lime instead of limestone and the “calcined
lime burning process” using quicklime powder instead oflimestone.
The calcined lime burning process was a method ofseparately calcining (decarbonizing) the limestone in alimekiln (shaft kiln) before mixing it with the clay. This
process was patented by Asano Cement in the late Meiji
Period and used with the company’s rotary kilns, not withshaft kilns. The calcined lime burning process is
significant because it was the pioneering technology
behind the NSP kiln, a Japanese technology thatflourished in the 1980s. See 4.2.5 and 5.2 for a moredetailed account of this.
New innovations in the dry process era included a tube
mill (Figure 3.3, also called a ball mill, see Note 2)
introduced by Asano Cement in 1899 and an
automatically coupled scale adopted by Onoda Cement
the same year for mixing raw materials. Later,
improvements were made in the fineness andhomogeneity of the raw mix with the adoption ofdifferent kinds of powder sifting machines.

Raw material preparation process

Water

Coal

Grinding

Limestone(slaked lime)

Blending

FormingDryingShaft kiln

Grinding

Weathering
storehouse

Packing

Weathering
storehouse

Packing

Bottle kiln, Dietzsch kiln, Hoffmann kiln
Clay

DryingGrinding

Coal

Grinding

Limestone(quicklime)

MixingClay

DryingRotary kiln

Grinding

Grinding* The pure dry process refers to the use of limestone as the raw material; the semi-dry process refers to the use of slaked lime as the raw material; and the calcined lime
burning process refers to the use of quicklime as the raw material.

Fig. 3.2 Dry-Process (Shaft Kiln/Rotary Kiln) Cement Manufacturing 2)

History of Cement Manufacturing Technology

14

barrels/cycle/kiln).
(Note) Records at the time are given in barrels, but the
net weight of the barrels varied with time (seeappended chronological table). Calculations here
are based on 380lb per barrel (172kg).

Fig. 3.3 Japan’s First Tube Mill 7)

3.2.2
The Shaft Kiln (Bottle Kiln) Burning Process(1) The Shaft Kiln Burning Method
The main kiln used for cement manufacturing in the
Meiji Period was the bottle kiln, such as the one shown in
Figure 2.8, which has been preserved at the Taiheiyo
Cement Onoda Plant. Built of brick and named for theresemblance to a liquor bottle, many of these were
15-20m in height. With the upper section comprising thesmokestack and the lower section comprising theso-called burning chamber, sticks of dead pine or otherkindling were placed on the fire grate with coal placed on
top as fuel, around two bricks deep, followed by raw
material blocks, five bricks deep. This was laid inalternating layers, and then the fire was lit in the fire grate.
After around five days of burning, the fuel would burnout and the burnt clinker could be removed from the grate
at the bottom. The clinker was sorted into “good quality”
and partially-burnt “poor quality”, with the good quality
product crushed to produce cement. Firing in this kiln wasa discontinuous (batch-wise) cycle, with the fire being lit
and burning out every cycle. Production capacity often
seems to have been 22-30 tons/cycle (130-180(2) The Number of Cement Kilns by Type in the Meiji
PeriodWhile bottle kilns (shaft kilns) were the main type ofkiln used for cement firing in Japan in the Meiji Period, as
mentioned previously, rotary kilns were introduced toJapan from the West in the late Meiji Period and rapidly
spread in use to become the main kiln used from the
Taisho Period onwards. Dietzsch kilns (shaft kilns) andHoffmann kilns were also used at some plants during the
Meiji Period.
Table 3.1 shows a summary of the cement kilns
constructed in Japan from the late Meiji Period to theearly Taisho Period at 17 plants operated by 12 cementcompanies with known histories.
As the table shows, the number of bottle kilns rose to
158 at 17 plants during the Taisho Period, accounting foraround 80% of all types of kiln. The cement industry
expanded rapidly as a result of the 1904-1905
Russo-Japanese War, with increasing demand for cement;
however, it was difficult to make shaft kilns larger due totheir shape. Companies responded by increasing thenumber of kilns, with one company, Aichi Cement,
installing as many as 49 kilns at its Higashi-Atsuta plant.
As shown in the table, the main kilns were bottle kilns,
with far fewer Dietzsch kilns and Hoffmann kilns.

Table 3.1 Number of Meiji-Era Cement Kilns Constructed (12 companies, 17 plants, as at 1913) 2)
Factory/plant name
Govt. Fukagawa Works Sub-Bureau
Asano Cement
Fukagawa Plant
Moji Plant
Onoda Cement
Onoda Plant
Dalian Plant
Mikawa Cement
Futatsuzaka Plant
Tahara Plant
Chuo Cement
Kawaguchi Plant
Kurosaki Plant
Aichi Cement
Shirotori Plant
Higashi-Atsuta
Plant
Hokkaido Cement
Hokkaido Plant
Sakura Cement
Osaka Plant(former) Nihon
Yatsushiro Plant
CementTosa Cement
Tosa Plant
Toa Cement
Amagasaki Plant
Iwaki Cement
Yotsukura Plant
Total

Bottle kilns(2l8)*
14
8
12
ņ
1
9
4
17
4
49

Dietzsch kilns
ņ
ņ
ņ
16
ņ
ņ
ņ
2
ņ
ņ
ņ

Hoffmann kilns
ņ
ņ
ņ
1
ņ
ņ
ņ
ņ
ņ
ņ
ņ

Rotary kilns
ņ
4

ņ
20
ņ

ņ
ņ
ņ

3
ņ
ņ

2
ņ
2

unknown
20
ņ
158

ņ
ņ
ņ
18

ņ
ņ
ņ
4

3
ņ
2
21

1
2
ņ
ņ
ņ
ņ
ņ
ņ

* After the government-managed Fukagawa Works Sub-Bureau increased from its initial two kilns to eight kilns, it was taken over by Asano
Cement, thus overlapping with the 14 kilns shown for that plant.

15

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March3.2.3

Shaft Kiln Era Finishing Process: Finishingby Weathering
Once burning was complete in a bottle kiln, the fire
grate underneath was removed and the clinker taken out.
Since bottle kiln burning was not uniform, the clinker had
to be taken out from the kiln and sorted. A steam-driven
fret mill (Figure 3.4, see Note 3) was used to grind theclinker. This could produce around 250kg (one barrel) of
product per hour initially, which could be increased to
500kg per hour with proficiency. The ground cement wassifted through a rotating hexagonal sieve, after which thefine powder was transported to the cement weathering
storehouse, while the remaining sieve residue wasreturned to the fret mill and ground again with newclinker.

(1) Grinding Clinker(2) Fret Mill Roller
Conserved on the
Taiheiyo Cement
Premises at Fukagawa,
Koto, Tokyo

Fig. 3.4 Fret Mill 7)

Since the fine powder thus obtained had to be properly
weathered before it could be used, meticulous attention
was paid to the weathering. The weathering method
involved setting up a weathering area, spreading out thecement at a depth of 0.1-1m and then occasionally turning
it to promote weathering. It was usually weathered foraround four weeks or longer, up to six months of more in
longer cases.
Cement powder had to be weathered like this for thefollowing reasons.
(1) The shaft kiln process often produced free lime
(see Note 4). There were concerns that the cement
would crack when hardened if used as is.
(2) Adjusting the setting time (see Note 5) within asuitable range when water is added.
Issue (2) above, as mentioned previously, was finallysolved in the 1890s with the addition of gypsum.
Weathering cement was the usual solution to the issue (1)until the late Taisho Period, when the amount of free limein the cement was reduced by the widespread use ofrotary kilns.
After weathering, the product had a stable lime content
and was packed into barrels in the weathering storehouse(Figure 2.11). Packing was also initially done manually.
Tube mills (Figure 3.3) began to be used in the late
Meiji Period (1900s) for grinding clinker, with use ofsteel balls, thus improving grinding efficiency and cement
quality.

3.3 The Arrival of the Rotary Kiln Era:
Innovative Technologies for
Mass-Producing High-Quality Cement2) 4) 5)

6)

Of the four processes used for manufacturing cement(raw preparation, burning, finishing and shipping), theburning process was the most significant in terms of costand product quality. In particular, the type of kiln had adirect impact on the quality and manufacturing cost of thecement. Accordingly, this has been constantly improved
upon since the dawn of the modern cement manufacturingindustry.
Cement burning is basically a solid-phase reaction,although in fact a partial liquid phase occurs at hightemperature, allowing the CaO / SiO2 reaction. In thesolid phase, mass transfer is more difficult to achieve thanin the liquid or gas phase, making it less susceptible tochemical reactions. With the shaft kiln, the raw materials
are formed into brick shapes, meaning there is almost no
mass transfer from external physical force during burning,making it difficult to have any chemical reaction between
solid particles. By contrast, with the rotary kiln,
developed in the United States in the late 19th century, theraw materials are loaded into the kiln in powder form andblended together by rotational force. This is a far morelogical method in terms of achieving a solid-phasereaction.
The use of rotary kilns for cement manufacturing is
superior to that of shaft kilns in many ways, including
kiln operation capability, fuel efficiency and quality
uniformity. Later developments in rotary kiln burningtechnology made it possible to mass-produce inexpensive
yet high-quality cement, thus ushering in the “concrete
civilization” of the 20th century.
With the introduction of rotary kilns enabling the mass
production of high-quality cement, the accompanying
developments in technologies and facilities for the raw
materials and finishing processes must not be overlooked.
The introduction of tube mills and other suchtechnologies as separators was particularly important.
3.3.1
The Introduction of Rotary Kilns 2) 4) 5) 6) 7) 8)
While rotary kilns were already being used for
calcining ore since 1881, it was in 1885 that FrederickRansome of the United Kingdom patented the use of therotary kiln for cement burning. After trialing anexperimental rotary kiln, he carried out an industrial trial
at a plant in Grays, Essex, England, with an experimental
kiln 18in (46cm) in diameter and 15ft (4.6m) in length.
He scaled this up to 48in (1.22m) in diameter and 30ft
(9.1m) in length, with successful results. However, thekiln never made it to implementation, as cement plants in
the United Kingdom at the time were manufacturing
using the wet process and he could not find a suitable
History of Cement Manufacturing Technology

16means of burning wet-process compounds in a rotary kiln,
combined with the fact that there were issues with theclinker fusing to the bricks due to the large amounts offuel required.
Further devices were contrived using this idea, withindustrial success achieved by Atlas Cement around 1890
at a plant in Rondout, New York, United States.
Production is reported to have commenced on a kiln 50in
(1.27m) in diameter and 50ft (15.2m) in length 8). The
first rotary kiln in Japan was imported from the UnitedStates in 1903 by Asano Cement and installed at the
Fukagawa plant. It was 6ft (1.83m) in diameter and 60ft
(18.29m) in length (Figure 3.5). This model was nearly
identical to the large-scale rotary kilns used today, with abrick-lined steel cylinder rotated at an incline of around
3%. The powdered raw materials were fed in from theupper end of the incline, with fuel burned in from thelower end (countercurrent heat exchange).

Fig. 3.5 Japan’s First Rotary Kiln (1903) 2)

Other companies in the industry gradually came torecognize that Japan’s first rotary kiln was superior to theexisting shaft kilns (including Dietzsch kilns andHoffmann kilns) in burning efficiency, capability andquality uniformity. Rotary kilns started being
incorporated into new facilities. It appears that they werealso being made progressively larger: a rotary kiln
constructed by Onoda Cement a decade later (1913) isrecorded as being 2.5m in diameter and 60m in length(Figure 3.6).

Fig. 3.6 An Example of a Rotary Kiln Constructed Ten
Years After Fig. 3.5 2)

17

Asano Cement was able to spearhead the introduction
RIURWDU\NLOQVWKDQNVWRHQJLQHHU)X\X]ǀ6DNDXFKLZKR
played a pioneering role in cement manufacturing
technology in Japan and at Asano Cement during the
Meiji Period, with achievements including leading the
introduction of “gypsum-adding” technology, as
mentioned later, and patenting the calcined lime burning
process.
3.3.2
Prevalence of Rotary Kiln
Figure 3.7 shows a summary of the trends in raw
materials processing and types of kiln up until 1917 for 8
companies and 14 plants with known histories as cement
plants.
Cement manufacturing in Japan started out with thewet process using bottle kilns, modeled on thegovernment-administered cement plants. From the late
1890s, this gradually transitioned to the dry process using
shaft kilns, and then to rotary kilns from around 1907.
The rotary kilns of this era were very thermally inefficientand were not definitely more cost-efficient than shaft
kilns either. It was not until the introduction of facilities
for waste heat utilization (waste heat power generation) in
1920 (see 4.2.2) that the rotary kiln era began in earnest.
By 1924, among the 20 companies (32 plants) thatwere members of the Japan Portland Cement Association,
29 plants had only rotary kilns, 2 plants had both bottle
kilns and rotary kilns and 1 plant (inactive) had only
bottle kilns. The bottle kiln era thus came to a close at theend of the Taisho Period (1926). The rotary kiln is
discussed in more detail from Chapter 4 onwards.

3.4 Adding Gypsum: The Other Major Invention
to be Introduced to Japan alongside“Portland Cement” and “Rotary Kilns”

2) 5)

Modern Portland cement contains around 3% gypsum.
This regulates the setting time of the cement to within atime range that makes it easier to use during construction.
The Portland cement invented by Aspdin (1824) only
comprised ground clinker, which meant it set very
quickly. The use of weathering to regulate the setting time
originated in the United Kingdom in the mid-19th century,
while a patent granted in 1870 in the United States for a“Mode of Hardening Artificial Stone and Other Articles,or Combination of Materials, by the Introduction of
Carbonic-Acid Gas”. Weathering in weathering areas waspracticed at plants in Japan from the Meiji Period to thelate Taisho Period, as mentioned in 3.2.3.
More detail on the European and American cement
industry’s “invention” of the mixing of gypsum toachieve cement setting consistency is given in 7.5.1.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

Year

T1

Reference

Company(Govt. managed) Fukagawa Works
Sub-Bureau

Cement manufacturing facilities
installed(Wet process) bottle kiln 6ROGWR6ǀLFKLUǀ$VDQR EHFDPH$VDQR&HPHQW(Wet process) bottle kiln

Asano Cement

Bottle kiln abolished(Dry process) rotary kiln

Fukagawa Plant(Dry process) bottle kiln

Bottle kiln abolished
Rotary kiln

Moji Plant(Wet process)bottle kiln

Onoda Cement
Onoda Plant

Hoffmann kiln
(M22-23)

Bottle kiln abolished(Dry process) Dietzsch kiln

Futatsuzaka Plant

Tahara Plant
Osaka Kawaguchi Cement Works(Wet process) bottlekiln

M22 Plant abolished(Wet process) bottle kiln

Rotary kiln installed / bottle kiln
abolished(Dry process) bottle kiln

(Wet process) bottle kiln

Plant abolished(Dry process) Dietzsch kiln
(Wet process) bottle kiln

Kurosaki Plant(Wet process) bottle kiln

Higashi-Atsuta
Plant

Hokkaido Cement

Rotary kiln installed(Dry process) rotary kiln

(Chuo Cement) Kawaguchi Plant

Aichi Cement Shirotori Plant

Dietzsch kiln abolished
Rotary kiln

Dalian Plant
MikawaCementRotary kiln installed(Dry process) bottle kiln

(Dry process) bottle kiln

Rotarykiln

Rotary kiln installed / bottle kiln
abolished

Rotarykiln

Rotary kiln installed / bottle kiln
abolished

Plant abolished(Dry process) bottle kiln

(Dry process) Hoffmann kiln

(Asano Cement) Hokkaido Plant

Sakura Cement

Hoffmann kiln abolished(Dry process) rotary kiln
Plant abolished(Dry process) bottle kiln

Osaka Plant
Tokuura Plant

Rotary kiln
Rotary kiln
M: Meiji Period; T: Taisho Period

Fig. 3.7 Trends in Raw Material Processing and the Types of Kiln in the Meiji and Taisho Periods 2)This technology was first introduced to Japan by Asano&HPHQWHQJLQHHU)X\X]ǀ6DNDXFKLZKRVWDUWHGXVLQJLWDW
the company’s Fukagawa plant when he returned fromstudying in Germany in 1888. However, it was initiallycriticized by some consumers in Japan as “adulterated”.
This criticism was not without cause, as the method ofusing gypsum to regulate setting was by no means perfectat that time. Later, studies on the composition of cement
revealed that setting occurs more quickly with a higher
alumina content and lower silicic acid content. Advanceswere made in increasing the silicic acid content andreducing the alumina content, thereby establishing themethod of using gypsum to regulate setting and making
setting more consistent.
These product improvements meant the abolition of theweathering method, previously used to prevent rapid
setting, early in the Taisho Period (1910s). The abolitionof weathering meant it was possible to manufacture
cement that set more consistently without sacrificing thestrength of the cement. The addition of gypsum to cement
was a major invention in cement manufacturing
technology, alongside the invention of the rotary kiln.
Chapter 7 discusses the cement retardation action of
gypsum in more detail.

3.5 Power Source: 2)From
Steam Engines to4) 5) 7)
Electric PowerThe early industry machinery of the Meiji Period was
powered by steam engines, with plants lit by lamplight. In
1899, Onoda Cement installed a 40kw DC generator at its
Onoda plant for partial electric lighting. Electric power
was first used to power the plant in 1911. The plant went

fully electric in 1913 with the installation of waste heat
power generation facilities 4).
Asano Cement is also reported to have started using
electric power around the same time 7). Thus, in theJapanese cement industry, the Meiji Period can be viewed
as the age of steam-power, and the Taisho Period onwards
as the age of electric power.

3.6 Cement Manufacturing Quality
Control and2) 6)
Cement Quality Standards

Since the beginning of Portland cement production in
Japan in May 1875, the quality of Japanese cement has
improved significantly throughout the Meiji and Taisho
Periods to the present day in the 21st century.
However, in the early years up until 1887, cementcompanies were starting completely from scratch, andthey ran their business and manufacturing operations on
an ongoing trial-and-error basis.
Production control started with the keeping ofnecessary records for material balancing, such as the raw
materials, fuel and products needed to keep the plant
operating. Later, as technology advanced, othermanagement items necessary for operation andmanagement were added, such as the operating hours of
main facilities.
The quality control was initially quite removed fromscientific controls. Tests began to be carried out on thestrength of cement, then chemical analyses were added aswell as physical tests, such as for fineness. The late 1890sand beyond saw the foundations laid for quality control,
which by the late Taisho Period (1920s) had beendeveloped to cover much of what it does today.

History of Cement Manufacturing Technology

18

3.6.1

Quality Control Up Until the Late 1880s and
Early 1890s
In the early era of cement, there was little awareness ofquality control. Up until around 1887 at least, test result
reports can be said to have been nonexistent.
From 1887 onwards, scientific controls graduallybegan to be implemented, with measurements taken of
raw material and cement fineness, cement chemical
analysis, mortar tension (strength) and hardening (setting).
However, companies were unable to conduct their own
chemical analyses, which had to be requested of the
Ministry of Agriculture and Commerce or otherorganizations. While companies were conducting theirown tests and qualitative evaluations, such as whether
hardening was rapid or gradual, the sand used for mortar
tests was not standardized, as it was chosen by eachcompany individually.
3.6.2
Towards Uniform Quality Testing Methods
Around the middle of the Meiji Period (1890s),
concrete construction was becoming quite popular, but nonational standards had been established for cement.
Accordingly, government civil engineers drew from theirknowledge of events in countries in which they hadstudied and emulated or revised cement standards fromthose countries, or else came up with their own testing
methods, leading to a diversity of methods. This was very
complicated, both from a technological perspective andan operational perspective, and was a major obstacle tocement company operation.
Under these circumstances, members of the cement
industry consulted together regarding uniform testing
methods. On July 15, 1893, eight prominent cementcompanies jointly signed and submitted a “Petition to
Unify Cement 7HVWLQJ0HWKRGV´WR6KǀMLUǀ*RWǀWKHQ
Minister of Agriculture and Commerce. Although this
proposal was not implemented, the industrial initiatives it
triggered had ongoing effects.
Around 1896, following consultation with members of
the cement industry and reference to the standards inGermany and other countries, a draft standard was drawn
up entitled “Appended Designation of Portland Cement
Testing Methods of the Empire of Japan”, on which the“Portland Cement Testing Methods of the Empire ofJapan”, proposed in July 1898 at a meeting of industry
members, was based.
The “Appended Designation of Portland Cement
Testing Methods of the Empire of Japan” firstly stipulated
the definition and composition of Portland cement, with
Articles 1-4 covering the test items of “setting”, “setting
capacity”, “strength testing” and “degree of powder”.
“Setting capacity” refers to expansion of cement paste
after hardening, while “degree of powder” refers to thefineness of the cement powder. The appended designation
stipulated factors such as the net weight of the barrels andthe attaching of trademarks. Similar test items were
defined in the “Portland Cement Testing Methods of the
Empire of Japan”.

19

Although this draft plan created by nine prominent
cement companies was never implemented,
manufacturers proceed with their day-to-day production
and quality control based on this industry proposal. The
testing system is thought to have gradually developed tocompletion from around 1897. At length, the government
also came to recognize the importance of quality
standards. Testing method research carried out by a teamof six engineers from industrial testing stations andcement companies resulted in the promulgation of the“Japan Portland Cement Testing Methods” by Ministry ofAgriculture and Commerce Notice No. 35 on February 10,
1905.
This was neither a law nor a regulation; it was simply agovernment purchase criterion that specified the quality
and testing methods for cement for government orders.
However, it was a standard set by government authority
and it gradually spread across to other consumers. Similar
in content to the “Portland Cement Testing Methods ofthe Empire of Japan” mentioned above, it comprised
Article 1 “Degree of Powder”, Article 2 “Setting”, Article
3 “Expansion Cracking”, Article 4 “Strength” and Article
5 “Limitations on Magnesia and Sulfuric Acid”. This
formed the basis of the present-day quality standards.
These testing methods were established around thesame time as the United Kingdom (1905) and the UnitedStates (1906) and triggered significant developments in
the Japanese cement industry, which had started later thanits counterparts in the West. Product quality rapidly
improved as manufacturing facilities improved, giving theJapanese cement industry a completely new look. As
cement quality improved, the cement standards became
successively more detailed, with relative weight and otheritems added and revisions made to standard values forfineness and strength.
The cement standards underwent later detailed
revisions and additions based on advances in technology
and needs of consumers, eventually taking shape tobecome the JIS standards of the present day. Chapter 8
discusses the history of cement standards in more detail.
3.6.3

Formation of Cement Technology
Organizations
In the first decade of the Japanese cement industry
coming into being, there was an overall low level ofscientific knowledge in the industry. There were very few
issues with the manufacturing or application of cementthat demanded scientific or technical research or
clarification. Cement manufacturers were carrying out
their own research, however, and the Japan Portland
Cement Industry Society was formed by ten companies in
the industry as early as 1900. The aim of forming theSociety was to set aside economic issues and to carry out
research in all academic and technical aspects of the
manufacturing and application of cement in order to steer
the development of cement and concrete in the right
direction.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

The first issues to deal with were selecting a standard
sand for cement testing and establishing the national
cement standards. Their efforts were rewarded with thepromulgation of the “Portland Cement Testing Methods”
by a Ministry of Agriculture and Commerce notice in
1905. Several years later, the Japan Portland Cement
Association was formed, which had strong business ties
with the Society. Although this organization was initiallyfounded as a friendly society for industry members, its
main involvement later shifted to inspecting cement
testing equipment, distributing the standard sand fortesting and promoting the utilization of cement. The twoorganizations continued until the age of wartime control,
making a significant contribution to the technologicaldevelopment of the cement industry.
During the war, both organizations were assimilated
into the Cement Control Association and were relaunchedright after the war in 1946 as the “Japan Cement
Technology Association”. This merged with the “Cement
Association” in 1966 to become what the “Japan Cement
Association” of today, with an associated “Research andDevelopment Laboratory”.
The main undertakings of the Laboratory today are as
follows.
1. Research and Technical Support
Holding cement technology conventions andlectures, administering research incentives andawards for papers, publishing collected papers on
cement and concrete, collaborative testing of
cement, etc.
2. Preparing Cement Standards
Preparing Cement Association standard testing
methods, managing and selling standard materials
and standard sand3. Commissioned Testing
Commissioned testing of cement and concrete

3.7 Cement Kiln Operational Performance in
the Meiji and Taisho Periods

1) 2)

Sections 3.1 to 3.6 above discussed the history of
cement manufacturing technology in the Meiji and Taisho
Periods. This period that dates back more than a century
and very few historical records survive that relate to
cement manufacturing during this time. Many of thedetails of the technology are unknown. However, since
Onoda Cement’s (now Taiheiyo Cement) Onoda plant hasremained on the same site at the same location since it
was established in 1881, quite a number of Meiji- andTaisho-era technical documents have survived. With thehelp of company retiree Dr. Tomikazu Dainobu, Taiheiyo
Cement began collating these records in 2004 andpublished a summary of the findings in the April, Julyand October 2008 and January 2009 issues of the

Taiheiyo Cement company bulletin CEM’s.
Although these are only records of one plant owned by
one company, they are considered to be very valuable
resources that reveal how the cement industry operated in
the Meiji and Taisho Periods. The main details are
outlined below.
(Note) Cement production at the Taiheiyo Cement Onoda
plant ended in 1985. Since then, it has been usedby associated companies for producing concrete
admixtures and additives and static crushingmaterials.
3.7.1
Bottle Kiln Operational Performance
Table 3.2 shows production performance between 1885
and 1894 in chronological order, including the transition
from wet process to dry process and scale-ups. “Numberof kiln outputs” represents the number of kiln operations
during that period, with the output from the kilns
categorized into good-quality “refined product” andinferior “under-burnt/over-burnt product”. The fuel ratio
is given as the quantity of coal required to burn one ton of
cement in kg units. Product weight was recorded by the
number of barrels at the time; this has been converted at
172kg per barrel and represented in tons (the same applies
below to rotary kilns).
As shown in Table 3.2, in a period of less than ten
years between 1886 and 1894, refined product volume byaround 13 times from around 626 tons to 8,415 tons. The
refined product volume per kiln also more than tripledfrom around 10 tons to around 34 tons. While a dramaticincrease in refined product volume was observed in 1890
in particular, this is believed to be due to the fact that the
number of bottle kilns increased from four to six that year,
as shown by the number of kilns in the table, the fact that
cement manufacturing shifted from the wet process to thedry process and the fact that some bottle kilns were madeto accommodate the growing demand for cement for theconstruction of railroads, harbors, cotton mills and otherdomestic facilities.
Although the inferior product rate varied a little year by
year, this steadily dropped from 25-30% in 1885 toaround 11% by 1893. Considering this reduction in
inferior product rate together with the increase in refined
product volume per kiln indicates that cement
manufacturing technology dramatically improved during
this time.
Fuel ratio trends for bottle kilns showed a wide rangeof variation between years, from 240kg to 519kg, withsome years having some records missing. This is thought
to be due to the bottle kiln burning method, namely, a
discontinuous or batch-type burning method, whereoperation has to stop at the end of each burning, thus
leading to significant variations in heat loss and output
clinker quality.

History of Cement Manufacturing Technology

20

Table 3.2 Bottle Kiln Production Performance 2)
Time
Year

No. ofkilns

No. of kiln
outputs

RefinedUnder- burnt /production
over-burnt
volume (a)volume (b)
(t)
(t)

Total
(c = a + b)(t)

Inferior
RefinedFuel
product rate
product per kiln consumption(b/c)(t/ operation)(kg/t)(%)

1885

2nd half4

Wet 39

366

130

496

26.2

9.4

404

1886

1st half4

Wet 37

352

135

487

27.8

9.5

519

nd

4

Wet 26

274

97

371

26.1

10.5

464

st

4

Wet 38

539

96

635

15.1

14.2

284

2 half
1887

1888

1 half
2nd half4

Wet 50

760

142

902

15.8

15.2

266

1st half4

Wet 60

941

271

1212

22.3

15.7

240
270

nd

4

Wet 56

870

259

1129

23.0

15.5

1 halfst4

Wet 47

743

248

991

25.0

15.8

364

2nd half4

Wet 51

838

227

1065

21.3

16.4

350

1st half

2 half
1889

1890

1891

1892

1893

1894

Wet process4

Wet 61

1161

233

1394

16.7

16.3

372

nd

6

Wet 34

649

134

783

17.1

19.1

(523)

6

Dry 63

1750

292

2042

14.3

27.8

(427)

st

6

Wet 2

32

9

41

21.9

16.0

-

2 half

1 half6

Dry 88

2632

497

3129

15.9

29.9

397

2nd half

6

Dry 74

2144

415

2559

16.2

29.0

395

1st half6

Dry 88

2776

452

3228

14.0

31.5

386

2nd half6

Dry 99

3195

391

3586

10.9

32.3

No record

1st half

7

Dry 102

9426

434

9860

11.2

33.6

No record

2nd half

7

Dry 103

3553

452

4005

11.3

34.5

No record

1st half

7

Dry 109

3856

705

4561

15.5

35.4

No record7

Dry 142

4559

860

5419

15.9

32.1

No recordnd

2 halfRaw material
production
methodBoth wet anddry process

Dry process

Notes) 1. The wet process was used until the first half of 1890; both wet and dry processes were used between the second half of 1890 and the first half of
1891; the dry process was used from the first half of 1891.
2. Entries in ( ) under fuel consumption are not full-year averages due to fewer records being available.

3.7.2
Rotary Kiln Operational Performance
Rotary kilns are characterized in that they cancontinuously produce consistent clinker because it ispossible to continuously feed in raw material and fuel andreduce or increase this input depending on the burning
conditions. There is no need for shaping the raw materials
or screening the clinker, thus simplifying the
manufacturing process and enabling mass production as aresult. Despite the drawback with the structure of the kiln
in generating a lot of radiant heat and being less thermallyefficient than shaft kilns due to the raw material shifting
to the bottom of the kiln while the hot gas rises to the top,
waste heat power generation that efficiently utilizes theheat energy of the waste gas has been implemented since
the start of the Taisho Period. Chapter 4 discusses theutilization of waste heat in rotary kilns in more detail.
(1) Rotary Kiln Operating Rate, etc.
The Onoda plant abolished shaft kilns in 1913, entering
an age of rotary kilns only. Table 3.3 shows the operating
performance of the No. 1 rotary kiln (diameter 3m, length50m) from that time until 1924. The table shows kiln
output, operating rate (ratio of rotary kiln operating time
per calendar time), coating (anzatz)-clearing wait time(see Note 6), coating-clearing wait time rate and fuel ratio
in chronological order.

21

Table 3.3 Rotary Kiln Production Performance 2)
Item

Kiln output

Operatingrate*

Coating-clearing wait
time

Fuel ratio

Wait time
Hours/ year
rate**(%)(kg/t)

t

t/day

(%)

1914

38131

129

81.3

1915

53082

177

82.4

1916

56459

179

86.1

1917

57845

188

85.6

473

6.4

289

1918

53148

176

82.9

308

4.3

297

1919

55842

180

86.0

407

5.5

281

1920

53947

174

85.2

208

2.8

285

1921

60266

191

87.1

356

4.7

291

1922

58698

185

88.7

220

2.9

292

1923

64159

195

89.7

221

2.7

1924

60266

184

87.5

Year
1913

No record

302
262
283

No record

262
282* Ratio of operating time per calendar time. Same as working ratio.
** Ratio of coating-clearing wait time per rotary kiln operating time.

The wait time rate under the “coating-clearing waittime” column is the ratio between the number of hours thekiln was temporarily stopped to manually clear theexcessive coating clinging to the inside of the kiln (onceper shift) and the number of operating hours of the kiln.
Although the operating rate rose from 81% when the kiln
was first installed to around 88-89% by 1924, it was
stopped more than three days per month. This was due tomany factors, including bricks dropping out of the innerwall of the kiln, breakdowns in machinery around the kiln
and shortages of raw materials. Specific to the operationof the rotary kiln was the regular extinguishing of the fire
for around 20 minutes per eight-hour shift (around one
hour per day) from 1917 to 1921 to manually scrape out

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchthe coating clinging to the interior of the kiln. The wait
time rate for the “coating-clearing wait time” was stillaround 3% (40 minutes per day) even in 1922. Rotarykilns rotated at the same fixed rate, but more proficient
control of the amounts of raw material and fuel input had
eliminated the need for coating-clearing by around 1926.
Thus, although cement burning in the Taisho Period(1912-1926) was more consistent than it had been in thepast, kilns still required repeated short breaks for clearing
coating or repairing mechanical breakdowns.
Rotary kiln operation (burning) logs also record thepressure used for blowing in the coal fuel from 1924
onwards. Since there are no records of temperature, it ispresumed that suitable temperature-measuring
instruments had not yet been developed and that the
inputs of raw material and fuel were controlled byobserving the burning conditions within the kiln and theclinker by eye.
(2) Rotary Kiln Output Trends
Since rotary kiln operation was consistent, there was noneed to sort the output after burning into superior andinferior products. The “kiln output” on its own wassynonymous with the “refined production volume” of thebottle kilns.
As shown in Table 3.3, the annual burning output roseto 38,000 tons in 1914, right after the rotary kiln started
operating, equivalent to around 130 tons per day. This isaround 3.7 times higher than the 35t/day achieved bybottle kilns. Burning outputs later gradually increased due
to increased operating proficiency, reaching around190t/day by 1923. At around 60,000 tons per year, thisdramatic increase was more than 1.5 times the annual kiln
output achieved in 1914.
The initial rotary kiln fuel ratio (kilograms of coal per
tons of cement) was slightly over 300kg/t-cement at thestart of rotary kiln operation in 1914, but remained
consistently below 300kg/t-cement after that. Comparedto the 240-519kg/t-cement achieved by bottle kilns,
regardless of the lower thermal efficiency of the rotarykiln compared to the shaft kiln due to its type, the fuelratio was actually lower and varied very little, meaningmuch more consistent operation compared to bottle kilns.
Note 1: MillA stone mill comprising a circular (diameter around 1.2m,
thickness 0.2-0.4m) runner stone with a raw material inlet at thecenter and a bed stone with radial grooves; the rotating of therunner stone would shear and grind the raw material, pushing
the powder out through the grooves to the edge.

Note 2: Ball Mill and Tube MillA ball mill is a general term for a rotating cylindrical crusher, inwhich the material to be crushed is inserted into the cylinder
together with balls as a crushing medium and is crushed by therotation of the cylinder. Ball mills in which the cylinder islonger than the diameter are called tube mills. Since most ballmills currently used at cement plants are tube mills, the termsball mill and tube mill are used interchangeably in this report.
Chapter 4.5.1 and Figure 4.12 provide more detail on theinvention of the tube mill, its introduction to Japan and thestructure of the mill.
Note 3: Fret Mill (Fig. 3.4)
Also called an edge runner. Two stone rollers around 1.2m indiameter rotate on a freely rotating stone table (later steel),crushing by compression and shear.
Note 4: Free Lime
Refers to unreacted lime (CaO) in clinker. An important part ofthe burning process is to cause the lime content of the raw
material to react with the clay content as much as possible toproduce hydraulic cement minerals. Clinker with very little freelime is termed “properly burnt clinker”. Excessive free lime cancause cracking in concrete.
Note 5: Setting and Hardening
The process from when water is added to cement until when the
cement hardens is called “setting”, while the process from when
it hardens and becomes stronger is called “hardening”.
Note 6: Coating (Anzatz in German)
This term refers to the fused raw material that has adhered tothe bricks on the inner wall of the kiln. At an appropriate
thickness, coating improves heat exchange by preventing raw
materials from sliding and also protects the surface of thebricks; however, when too much adheres, it can prevent theflow of raw material within the kiln, thereby reducing thecapacity of the kiln and lowering the production efficiency.

References (all in Japanese)1) Tomikazu Dainobu, Trends in Cement Manufacturing
Technology in the Meiji and Taisho Periods,
Yamaguchi University doctoral dissertation, 2007.
2) Tomikazu Dainobu, “Trends in Cement
Manufacturing Technology in the Meiji and Taisho
Periods”, CEM’s (Taiheiyo Cement Technical
Information ), No. 37-40, 2008-2009.
3) Sutezo Sugishita, Cement Industry in Japan, Poplar
Publishing, 1962.
4) Onoda Cement Co., Ltd., 100-Year History of Onoda
Cement, 1981.
5) Takashi Ueno, Supplement to the History of Cement
Technology, Onoda Cement, 1980.
6) Minoru Fujita, Cement, Yuhikaku Publishing, 1960.
7) Nihon Cement Co., Ltd., 100-Year History of Nihon
Cement, 1983.
8) Mitsuzo Fujii, “Development History of Portland
Cement (1)-(18)”, Cement & Concrete, No. 105-130,
1955-1957.

History of Cement Manufacturing Technology

22

4

From the Early Showa Period and the Pacific
War to the Post­War Reconstruction Period(1926­1960)

The previous chapter discussed cement manufacturing
technology in Japan from its origins with the bottle kiln
through to 1926. During this time, the following
significant advances were made.
(1) Mass production of cement was made possible
through rotary kiln
(2) Setting and hardening were made more consistentby adding gypsum(3) Quality improved with the establishment of quality
testing methods and quality standards.
Production volumes, which in 1882 had totaled around3,000 tRQVSHU\HDUEHWZHHQ6ǀLFKLUǀ$VDQR¶V)XNDJDZD
plant in Tokyo and Junpachi Kasai’s Onoda Cement plantin Yamaguchi, increased to 600,000 tons by around 1912
and 3 million tons by 1926, with plants being built all
around the country.
This chapter discusses the trends in domestic Japanese
cement manufacturing technology from the late 1920s
through the Pacific War to 1960 and the end of the
postwar reconstruction period. The following four points
can be identified as significant to the development of
manufacturing technology during this time.
(1) Advances in the technological development ofrotary kiln exhaust heat (waste heat) recovery andutilization methods. Several types of rotary kilns
emerged with different systems.
(2) Advances in improving technology for preceding
and following processes, as achieving mass
production using rotary kilns required sufficiently
capable raw materials and finishing processes.
Dust collectors were also fitted due to pollution
issues as plants expanded in scale.
(3) Diversification of the types of cement as theapplications for concrete grew.
(4) Although most cement manufacturing technologies
were still being introduced from the West until thistime, a “new calcined lime process”, using
calcined quicklime instead of limestone was aforerunner for later technological developmentsthat were uniquely Japanese.
(Note) In 1909, Onoda Cement constructed its Dalian Plant
and commenced operation in what was then the
Kwantung Leased Territory (now northeastern
China). Although Japanese cement companies later
expanded into Taiwan, the Korean Peninsula andManchuria (now northeastern China) between the
1910s and the Second World War, building newplants in various areas, the facilities andtechnologies adopted there are not covered in thisreport, which focuses on the idea of “in Japan first”.

4.1 The Cement Industry from 1926 to 1960 1) 2)

Figure 4.1 shows the transitions in cement production
volumes during this period. Production rose from around3 million tons in 1926 to around 6 million tons by 1937.
However, although the cement industry had favorable

23

growth in production volumes, as the figure shows,cement company fortunes were tempestuous from the
Meiji and Taisho Periods through to the Second World
War. The economic recession that began in 1920 after theFirst World War, the Showa financial crisis of 1927 andthe worldwide Great Depression that began in 1929 had
an ongoing impact; this coupled with unregulatedcompetition to increase production and dumping sales
meant hardship for smaller manufacturers, with many ofthem either being taken over by larger companies orclosing down altogether.
With the outbreak of the Second Sino-Japanese War in
1937, the Japanese economy shifted into a wartime
regime. Like other industries, the cement industry was
subjected to national control, with restrictions placed on
all aspects, including production, sales, prices andallocation of materials. As Japan entered the Pacific War,business operators entered a time of severe difficulty. The
war meant a forced decline in domestic cement operations,with severe restrictions imposed, including (1) reduced
allocation of raw materials and decreased production, (2)curtailment of business operations (compulsory mergers)and (3) enforced relocation of plants toJapanese-occupied territories in the south by militaryorder.
Japan’s defeat in the war struck a devastating blow to
the cement industry. Numerous overseas plant assets(many of them new facilities) were lost in a single stroke.
Although plants on home soil suffered relatively little
direct damage from bombs or other attacks, themachinery and facilities were run down from overuse
during the war and production volumes dropped
dramatically. Monthly production at the end of the war
fell to 30,000 tons (from a prewar average of 300,000
tons), with annual production volume for 1945 eventually
dropping to around 1 million tons, including the time
before the war ended and afterwards.
However, once the controls on coal fuel were lifted in
September 1949, production conditions rapidly improved
and monthly production rose to 300,000 tons once more.
In 1950, the controls on cement price and distribution
were lifted and free selling was reinstated. In 1951,
annual production reached 6.5 million tons and surpassed
the prewar peak.
With the controls lifted, the Japanese cement industry
made astounding progress. First of all, the domestic andinternational demand for cement grew rapidly. Rebuilding
waterways, roads, harbors and other infrastructure that
had been damaged in the war required large amounts of
cement first and foremost, as did the construction ofrailroads and dams to facilitate economic recovery andthe reconstruction of homes and factories. This
“reconstruction demand” was also further spurred on by
the favorable domestic economy that resulted from the
Korean War that started in 1950.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

10,000 tons

10,000 tons
1926
(fiscal year)

1930

1935

1940

1945

1950

1955

1960

January – December

Fig. 4.1 Transitions in Cement Production Volumes 1926-1960 1)

From 1951, annual production volumes increased in an
unprecedented steep curve. Domestic demand increased
at an average of around 17% from 1951, more thandouble the prewar growth rate of around 8%.
The first factor cited for this surge in demand is thesoaring reconstruction demand. However, the growthfrom 1956 onwards, a decade after the war, indicates thepresence of another underlying factor with moreaggressive demand: expanding the Japanese economy,
along with public investment into roads, harbors, dams
and other industrial facilities to support this.
Meanwhile, cement exports resumed in 1947 andsteadily increased each year to reach 2.2 million tons in
1956, making Japan the world’s largest exporter of
cement. The cement industry was well able to manage
this sudden growth in demand by increasing production.
Great success was achieved after the war with efforts toreinstate management systems, rebuild facilities andactively expand.

4.2 Development of Cement Burning
Technology (from the late 1920s to the1) 2)

1950s)In 1903, Asano Cement installed Japan’s first rotarykiln (diameter 1.8m, length 18.3m), imported from theUnited States, as discussed in 3.3 above.
After that, rotary kilns spread in popularity among
companies until they completely superseded theconventional shaft kilns by the late 1920s, as also
discussed in 3.3 above. Thus, the emergence of rotarykilns brought about a major transformation in the historyof cement manufacturing technology. This enabledcement plants to transition into “mass-production
facilities” with rotary kilns at the core.
In 1920, Onoda Cement installed the first private
power generation facilities at its Onoda plant, utilizing
waste heat from rotary kiln exhaust gas. Japan was facing
a shortage of electric power at the time and this method ofwaste heat power generation (see 4.2.2) did not go
unnoticed. Waste heat power generation became morewidespread until eventually most rotary kilns were fittedwith waste heat boilers.
Many rotary kilns used the dry process (the method ofloading dry, powdered raw materials into the kiln).
However, with the use of “high-early strength cement”(details in Chapter 8) becoming more common in Europe
from around the late 1920s, Asano Cement attempted to
manufacture it in 1929 by loading raw material slurry into
a rotary kiln. The company established a wet process

History of Cement Manufacturing Technology

24plant in Nishitama, Tokyo. In 1932, Onoda Cement
installed the first “slurry filter” on wet process kilns at its
new Fujiwara plant in Mie, making waste heat power
generation possible with the wet process. This filter
method later became a common choice for the wet
process.
In 1934, Mikawa Cement (later merged with Onoda
Cement) established Japan’s first “Lepol kiln” at its
Tahara plant. The innovation of the Lepol kiln was theuse of a preheater for exhaust gas heat recovery for the
first time in history. A preheater is a device that transfers
the heat from the kiln exhaust gas to the raw materials byconduction, thus decarbonizing or “calcining” thelimestone.
Table 4.1 shows the types of kilns used from the late
1920s to the present day. This section discusses the “dryprocess”, “wet process” and “semi-dry process” in termsof the trends and developments in each from the late
1920s to the 1950s and the different issues with each of
the processes. The Japanese cement industry overcame
these issues and went on to successfully develop the NSP
method at the peak of modern cement manufacturing
technology today, discussed in Chapter 5.
Table 4.1 Categorization of Cement Kilns by Type (late1920s-) (source: author)

Dry process kiln
* Short kiln
Waste heat boiler attached (DB)New calcined lime burning process (NCB)
Suspension preheater attached (SP, NSP)
* Long kiln
* Shaft kiln (S)Wet process kiln
* Short kiln
Filter attached (WF)
Filter attached, boiler attached (WFB)* Long kiln
Semi-dry process kiln
* Lepol kiln (L)Note: Parentheses show the abbreviations used in theJapanese cement industry for each type.

(Note) The “shaft kiln” in the table is not the Meiji-era
shaft kiln (bottle kiln), but a shaft-type kiln built
by some cement companies for a short time after
the end of the war using licensed technology from
Germany. Although cheaper to build and more
thermally efficient than other types of kilns, they
stopped being used after about a decade due toissues with operability and cement quality. They
have not been mentioned in detail in this chapter
due to being overseas technology and having hadvery little impact on other manufacturing
technologies. Also, although there have been some25

cases of “dry process long kilns” in the UnitedStates, they were not used in Japan and so havealso not been mentioned in detail. SP and NSP
kilns are discussed in detail in Chapter 5.
4.2.1

Improving Thermal Efficiency and Reducing
Fuel Consumption of Rotary Kilns
The introduction of rotary kilns was an epoch-making
event in the history of cement manufacturing technology
in the sense that it improved cement quality and mademass production possible. However, despite these majoradvantages, there were several drawbacks with rotarykilns, the most significant being their poor thermal
efficiency. There two factors allowing heat to escape:“heat retained in exhaust gas” and “heat retained in theclinker”.
(1) Heat Retained in Exhaust Gas
In a rotary kiln, the chemical reaction between the raw
materials is caused by countercurrent heat exchange
between the raw materials traveling to the bottom of thecylinder and the burnt gas traveling to the top. Most of theheat transfer between the burnt gas and the raw materials
is due to radiative heat transfer from the combustion
flame, with conductive heat transfer playing a very smallrole. While the gas temperature drops toward the gas exitof the kiln, the radiative heat transfer rate between the gas
and the material drops proportional to the fourth power of
the absolute temperature. This consequently makes theheat exchange rate low and the thermal loss high.
(2) Heat Retained in the Clinker
The hot clinker burnt in a rotary kiln is cooled by the
air on coming out of the kiln. The cooling air is drawn
into the kiln as secondary air (see Note 1). There is a low
rate of radiative heat transfer between the hot clinker andthe air being drawn into the kiln; sometimes the clinker
comes out of the kiln still very hot. Consequently, thisthermal loss is also very high.
Fuel costs account for a high proportion of the
manufacturing costs of cement. Therefore, improving thethermal efficiency of rotary kilns and reducing theamount of heat required are very important factors for
reducing costs. This section 4.2 discusses the measurestaken to recover heat retained in the kiln exhaust gas,
while the following section 4.3 discusses the measurestaken to recover heat retained in the clinker.
4.2.2

Power Generation from Exhaust Gas Heat
in Dry Process Rotary Kilns (Dry Process
Kiln with Waste Heat Boiler Attached / DB) 2)
3)

Dry process rotary kilns (short kilns) with waste heatboilers attached (DB) were the main kilns used from the

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchheat boilers and either purchasing power from external
electricity companies or supplying it with efficient
generators. Consequently, dry process kilns with attachedboilers were gradually phased out with the transition tosuspension preheater (SP) kilns from the 1970s onwards.
The next chapter (Chapter 5) discusses suspension
preheater kiln waste heat recovery in the section on
cement manufacturing technology during Japan’s postwar
economic growth period. Figure 4.2 shows a schematic
diagram of a dry process kiln with attached boiler, while
Table 4.2 provides an example heat balance.

late 1920s to the postwar reconstruction period. Sincemany dry process kilns were 70-80m long, the exhaustgas was around 800-900ºC, around 50% of the amount ofheat being blown into the kiln. To efficiently utilize thisexhaust gas heat, a method was developed of mounting aboiler at the kiln end (gas exit) to generate electricity.
American boiler manufacturers and other companies
marketed this technology in the 1910s. Despite the FirstWorld War delaying its introduction to Japan, the first
boiler was installed at Onoda Cement’s Onoda plant in
1920 and it was subsequently widely adopted by plants allover the country.
Using this method allowed 60-70% of the exhaust gas
heat to be recovered, making it possible to generate
120-150kWh of electricity per ton of clinker, enough toprovide around 90% of the electricity needed for one kiln
system, from the raw materials process to the finishingprocess. Accordingly, plants began shifting away fromsteam-powered machinery to electric-powered machinery.
Despite power shortages during the Pacific War and thetime that followed, cement production lacked only for
coal; the benefit of waste heat power generation was thecapability to continue producing steadily due to being
almost self-sufficient for electricity.
However, from the late 1950s at the end of the postwar
reconstruction period, ideas began to change regarding
rotary kiln heat recovery. Rather than indirectly utilizing
waste heat for power generation, it was morecost-effective to lower the exhaust gas temperature as
much as possible to increase thermal efficiency. Boilers
attached directly to rotary kilns were an impediment tolong-term operation, because the high-temperature dust
particles in the exhaust gas caused a lot of wear on the
boiler pipes. The best option was to ensure long-term
rotary kiln operation by discontinuing the use of waste

4.2.3

Wet Process: The Slurry Filter System andthe Long Kiln System 2) 3) 4) 5) 6)
In 1929, Asano Cement adopted a wet process for
manufacturing high-early strength cement at its Nishitama
plant in Tokyo. With the technology level at the time, it
was easier to mix and grind raw materials in the wet
process than in the dry process; the wet process also
produced a far better quality product. However, the dry
process required less heat for burning, while the wet
process consumed 15% more fuel. The wet process alsooffered little power generation using waste heat boilers
and lower clinker burning volume per rotary kiln unit
capacity. The wet process kiln was selected for
manufacturing high-early strength cement, on theassumption that it could be sold as “high-performance
cement” for a higher price than ordinary cement.
“Wet process kilns with attached slurry filters” and“wet process long kilns” attempted to leverage the wet
process advantage of “burning good-quality clinker” tosurmount the drawbacks of “high fuel consumption” and“poor production capacity”.

Raw material
powderPrimary air fan
Cooler exhaust gas fan

Waste heatboilerElectrostatic
precipitator

Rotary kiln

Fuel

Air-quenching cooler

Exhaust gas fan

Cooling fan

ClinkerFig. 4.2 Dry Process Kiln with Attached Boiler 3)
Table 4.2 Example Heat Balance for a Dry Process Kiln with Attached Boiler 3)
Heat balance (low calorific value)
Input heat Q1

3718m
25.5t/d3
35.5kg/m h
1,517 × 103kcal/tcl’29.4%
22,063m2
23.8kg/cm
70%
20%
17.5t/h120kWh/tcl’

Output heat Q2.LOQVL]Hĳîĳî
Effective capacity (shell capacity):
Clinker output:
Specific clinker output:
Firing heat (low calorific value):
Burning efficiency:
Boiler heat transfer surface area:
Steam pressure:
Boiler efficiency:
Turbine efficiency:
Evaporation:
Power generated:

Heat from fuel combustion Qa
Sensible heat from fuel Qb
Sensible heat from raw materials Qc
Sensible heat from primary air Qd
Total
Heat used for burning clinker Qe(Sensible heat from clinker entering the cooler)
Qf
Heat escaping in the clinker Qg
Heat escaping in the cooler exhaust Qh
Raw material moisture evaporation heat Qi
Heat escaping in the kiln exhaust gas Qj
Dust, emissions, other Qk
Total
୕ୣିୡ

Burning efficiency ୕ୟ × 100

x 103
kcal/tcl’
1517
4
3
ņ
1524
449

%
99.5
0.3
0.2
ņ
100.0
29.5

(289)

(19.0)

19
26
0
739
291
1524

1.2
1.7
0
48.5
19.1
100.0

ņ

29.4

History of Cement Manufacturing Technology

26

(1) Wet Process Kiln with Attached Slurry Filter(WFB)
In the wet process, evaporating moisture content
consumes around 2,100kJ (500kcal) of heat per 1kg ofclinker. To reduce this, a method was devised that used afilter to filter out the moisture content of raw material
slurry. Although wet process filters had long been used inmining, they were first adopted by the cement industry in
the United States in 1925.
Onoda Cement installed Japan’s first wet processrotary kiln with attached slurry filter and waste heat boiler(WFB) at its Fujiwara plant in Mie in 1932, achieving
success with the wet process comparable to the dry
process in terms of heat used and waste heat power
generation. After that, many wet process kilns were
installed with filters attached. Records indicate that when
Asano Cement changed the existing wet process kiln at its
Nishitama plant to one with a filter attached in 1933, thefilter reduced the moisture content of the raw materials by
up to 20%, thereby reducing fuel costs by 15%,
increasing production by 20% and generating 20% more
electricity.

(2) Wet Process Long Kiln (W)The simplest method of reducing exhaust gas
temperature and increasing thermal efficiency is to makethe rotary kiln longer. Many of the kilns in postwar Japan
were so-called short kilns, 60-80m in length. Following
the installation of a long kiln (135m) by Tokuyama Soda
at its Tokuyama plant in 1954, long kilns began to bebuilt in increasing numbers. When a long kiln is used, theraw material slurry is poured directly into the kiln. By theearly 1960s, the heat usage had improved to 5,440kJ(1,300kcal) per 1kg of clinker, while exhaust gas
temperature had dropped to 160ºC. There were also no
issues with boilers, since there was no waste heat power
generation. The use of slurry simplified the raw materials
process and also meant the raw material fed into the kiln
was highly consistent. Further, kiln operation without thetroublesome boiler made long-term operation possible,
making this kiln far more competitive than other types ofkiln and earning it the name of “economical long kiln”.
Figure 4.4 shows a schematic diagram of a wet process
long kiln, while Table 4.3 provides an example heatbalance. Figure 4.5 shows a photograph of this type ofkiln.

Fig. 4.3 Slurry Filter on a Wet Process Kiln with Attached
Boiler 7)

Chain section

Raw material slurry
Electrostatic
precipitator

Rotary kiln
Preheater

Air-quenching cooler
ClinkerFig. 4.4 Wet Process Long Kiln 3)
Table 4.3 Example Heat Balance for a Wet Process Long Kiln 3)

Input heat Q1

Heat balance (low calorific value)

Output heat Q2.LOQVL]Hĳîĳĳî
3
Effective capacity (shell capacity):
1730m
Clinker output:
30.0t/h3
Specific clinker output:
17.4kg/m h3
Firing heat (low calorific value):1,269 × 10 kcal/tcl’Burning efficiency:
33.4%
Preheater:
Smith type3
Chain heat transfer surface area:
1,660mHeat from fuel combustion Qa
Sensible heat from fuel Qb
Sensible heat from raw materials Qc
Sensible heat from primary air Qd
Total
Heat used for firing clinker Qe(Sensible heat from clinker entering the cooler)
Qf
Heat escaping in the clinker Qg
Heat escaping in the cooler exhaust Qh
Raw material moisture evaporation heat Qi
Heat escaping in the kiln exhaust gas Qj
Dust, emissions, other Qk
Total

x 103
kcal/tcl’
1269
2
15
4
1290
440

98.3
0.2
1.2
0.3
100.0
34.1

(291)

(22.5)

13
46
524
146
121
1290

1.0
3.6
40.6
11.3
9.4
100.0

ņ

33.4

୕ୣିୡ

Burning efficiency ୕ୟ × 100

27%

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchFig. 4.5 Photograph of a Wet Process Long Kiln (Kiln
Length 170m) 7)

4.2.4
Semi-Dry Process: Lepol Kiln (L) 2) 3)
The innovation of the Lepol kiln was the use of apreheater for exhaust gas heat recovery for the first timein history. A preheater is a device that transfers the heatfrom the kiln exhaust gas to the raw materials byconduction, thus decarbonizing or calcining the limestone.
The name comes from the names of the inventor Georg
Lellep (Germany) and the plant manufacturer Polysius(Germany).
Lepol kilns (Figure 4.6) have a movable grate(indicated as “preheater” in Figure 4.6) fitted at the end of
the kiln (the rotary kiln exhaust gas outlet = raw materials
intake). Moisture content of around 14% is added to theraw materials, which are then made into pellets using apelletizer and spread on the floor of the grate to a
thickness of around 20cm. Exhaust gas is drawn throughthe grate from above and heat exchange takes place as thegas passes through the layer of raw material. The raw
materials fed into the kiln are preheated to over 900ºC,
while the exhaust gas drops to around 200ºC, thereby
reducing fuel consumption. The rotary kiln can also bemade shorter, to around 10-13 times the diameter. The
first Lepol kiln to be erected in Japan was at the Mikawa
Cement Tahara plant in 1934. After the war, Lepol kilns
became quite widespread throughout Japan, with Iwaki
Cement (now Sumitomo Osaka Cement) using Lepol
kilns almost exclusively in its new plant in Hamamatsu,
Shizuoka, as well as at its plants in Yotsukura(Fukushima), Tochigi and Nanao (Ishikawa). The reason
for this was the low heat usage, as low as 4,200kJ/t-cl(1,000kcal/t-cl). However, Lepol kilns had the following
drawbacks.
(1) The raw material (clay) had to have very good
granular properties, which placed limitations on
the site location and raw material preparation.
(2) Since the preheater grates operated at hightemperatures of 900-1000ºC, the larger they were,the more susceptible they were to mechanicalbreakdown, making it difficult to scale up the sizeof the kiln (maximum capacity of around
1,200t/d).
Due to reason (2) above, Lepol kilns were phased outof the Japanese cement industry from the 1980s onwards
with the rise of large-scale SP and NSP kilns capable ofproducing over 3,000t/d.
Figure 4.6 shows a schematic diagram of a Lepol kiln,
while Table 4.4 provides an example heat balance.

Auxiliary stack

Primary
exhaust fan
Pellets

Preheater

Rotary kiln

Raw material
powderPelletizer

Air-quenching cooler

Clinker

Secondary exhaust fan

Fig. 4.6 Lepol Kiln 3)
Table 4.4 Example Heat Balance for a Lepol Kiln 3)3Heat balance (low calorific value)
Input heat Q1

3837m
50.2t/h360.2kg/m h3
884.5 × 10 kcal/tcl’
48.1%
3,804 × 29,252

Output heat Q2.LOQVL]Hĳî
Effective capacity (shell capacity):
Clinker output:
Specific clinker output:
Firing heat (low calorific value):
Burning efficiency:
Grate size:

Heat from fuel combustion Qa
Sensible heat from fuel Qb
Sensible heat from raw materials Qc
Sensible heat from air bursts Qd
Total
Heat used for burning clinker Qe(Sensible heat from clinker entering the cooler)
Qf
Heat escaping in the clinker Qg
Heat escaping in the cooler exhaust Qh
Raw material moisture evaporation heat Qi
Heat escaping in the kiln exhaust gas Qj
Dust, emissions, other Qk
Total
୕ୣିୡ

Burning efficiency ୕ୟ × 100

x 10
kcal/tcl’
875.6
3.6
15.3
ņ
884.5
426.3

%
99.0
0.4
0.6
ņ
100.0
0.6

(393.1)(38.8)

8.5
120.4
134.1
76.3
126.2
884.5

0.6
13.8
15.2
8.7
13.6
100.0

ņ

48.1

History of Cement Manufacturing Technology

28

New Calcined Lime Burning Process (NCB):
The First Domestically-Developed
Manufacturing Technology 4) 5) 8)
All of the cement manufacturing methods discussed
thus far have involved the “raw limestone burning process”
of crushing the limestone in its natural state, mixing itwith clay and then feeding it into the kiln. By contrast, the“calcined lime burning process” involves calcining thelimestone in advance in a limekiln to produce quicklime,
which is then mixed with clay and burned in the kiln. In
the conventional cement burning process, around 50% of
the heat is used in decarbonizing the limestone.
Converting the limestone to quicklime using a more
thermally efficient shaft kiln reduces the overall heatusage. Quicklime is also far softer than limestone, thereby
reducing the amount of power used for grinding.
Asano Cement patented the calcined lime burning
process in 1907 and implemented it at its Moji plant.
Records indicate that the process increased the production
output without needing to increase the capacity of therotary kiln and accordingly spread throughout thecompany’s other plants as well 4). However, there weresome issues recorded: (1) proportioning of raw materials
tended to disperse; (2) calcining the limestone waslabor-intensive; and (3) it required coke. Reports indicatethat Asano Cement consequently adopted the ordinary
limestone burning processes at all of its new plants built
from the late 1920s on and abandoned the calcined lime
burning process around the late 1940s.
In 1956, the president of Onoda Cement, Toyoroku$QGǀ ZLWKDQHQJLQHHULQJEDFNJURXQG QRWHGWKH
advantages of the calcined lime process, namely, its
superior thermal efficiency and increased output, andcommissioned his technology team to try to surmount the
problems with the process and see it through to practicalimplementation. In addition to the issues (1), (2) and (3)mentioned above, there was also the issue of (4) the
limekilns of the day were too small to be used for mass
production of cement.
The technology team searched the literature to
successively develop a test plant, a miniature plant andthen a small-scale plant and was able to solve the issues,
except for the use of coke, as outlined below.
(1) The team successfully developed the technology
for large-scale limekiln (shaft kiln, 350t/d) tosupport mass production of quicklime.
* Successfully achieved “consistent burning inevery corner of the shaft kiln”, difficult toachieve in conventional shaft kilns.
* From the quality perspective, “uniform
calcination” was made possible.
* “Automation” introduced to the limekiln
operation; processes developed to enableefficient operation by a small workforce.
(2) The team used an air-blending method (see 4.8) tomix the quicklime powder with the clay powder(Japan’s first “continuous blending”), ensuring

29

product quality matching that of any other type ofkiln.
(Note) In the ordinary kiln process, the limestone and theclay were ground together. In the new calcined
lime process, the quicklime and the clay wereground separately and then blended in the proper
proportions. It was essential to have equipment that
could blend quicklime powder and clay powder as
homogeneously as possible.
Natural coke and anthracite were examined in regards
to the cited issue of fuel; however, since no steady supplyof these could be expected, implementation went aheadusing coke as fuel. Figure 4.7 shows a photograph oflimekilns used in the new calcined lime process.

Fig. 4.7 Limekilns for the New Calcined Lime Process 7)

When Onoda Cement converted its existing dry processkilns with attached boilers (DB) to the new calcined lime
burning process (NCB), it turned out that the production
approximately quadrupled with the same kiln. From 1959
to 1961, Onoda Cement converted a total of ten rotarykilns at its plants in Fujiwara, Tsukumi, Onoda andOfunato to the NCB process and approximately doubled
its cement production in three short years, from 2.7
million tons in 1959 to 5.15 million tons in 1962 (Figure4.8). This was the result of converting to the NCB process.
The company’s shares also rose accordingly, leaping up
3%-points in 1960.
(10,000 tons)

4.2.5

Nihon

Onoda

Sumitomo
Onoda production volumes

1956

1957

1958

1959

1960

1961

1962

1963

1964

Fig. 4.8 Onoda Cement Production Volumes and Shares
Before and After Implementing the New Calcined Lime
Burning Process 5)

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

However, with trade liberalization in 1961 and the“energy revolution” providing cheap and easy access tofuel oil, companies quickly shifted from coal to fuel oil tofuel their rotary kilns (see 4.9). With this upheaval in thefuel situation, the NCB process using coke-fueled shaft
kilns was at a disadvantage to other types of kilns from afuel cost perspective due to the rising price of coke.
Instead of expensive coke, efforts were made to develop
technology using oil-fueled limekilns or using pellets
made from cheap oil coke (see Note 2) to fuel the
limekilns, with limited success. Ultimately, theemergence of the innovative technology of SP and NSP
kilns meant the abolition of NCB kilns and other types ofkilns by the late 1970s.
The calcined lime process, patented by Asano Cementand developed by Onoda Cement, was the first native
Japanese manufacturing technology in the history of theJapanese cement industry, the industry having relied on
introduced technology since the Meiji Period (1870s).
This is of noteworthy importance, as it paved the way forthe various other “native Japanese” cement manufacturing
technologies that began to blossom in the 1980s, the NSP
kiln in particular. Strong leadership demonstrated by
2QRGD&HPHQW&RSUHVLGHQW$QGǀKDVEHHQDWWULEXWHGWR
somehow making it possible to overcome many financial
and technical difficulties faced in the technologicaldevelopment process. This technological development
meant that mechanical, electrical and chemical engineers
could now be involved at the machinery/equipment
design stage rather than just being machinery/equipment
users, leading on to further developments in “native
Japanese” cement manufacturing technology.
In 1976, Onoda Cement made its engineering
department into a separate entity, Onoda Engineering(now Taiheiyo Engineering), with the aim of taking its
technology developed since the NCB process marketing itin Japan and overseas. Later, other companies alsoestablished similar subsidiary companies.

were made to effectively recover this residual clinker heatand improve the thermal efficiency of rotary kilns. The
planetary cooler and air quenching cooler (AQC) weredeveloped in the United States and introduced to Japan inlate 1920s, and both of these coolers made a significant
improvements in terms of the amount of heat recoveredfrom the clinker. These coolers were intended to makemaximum use of conductive heat transfer between theclinker and the air.
Below is a summary of the development of clinker
residual heat recovery technology, or clinker coolers.
4.3.1

The Era of Rotary Kilns and Standalone
Coolers
Early rotary kilns did not have coolers for recovering
and utilizing the waste heat from clinker cooling, but only
had nearby devices for cooling the high temperatureclinker coming out of the kiln.
4.3.2

The Era of Rotary Cylinder Coolers(Under-Coolers) Connected in Series
In this cooling system, the high temperature clinker
dropped out of the rotary kiln into a rotating, cylindricalcooler fitted underneath the kiln. Air from a blower
cooled the clinker through countercurrent heat exchange
and was drawn into the kiln as secondary air. Recovering
the residual heat in the clinker as secondary air improved
thermal efficiency. However, the single cylinder was not
sufficient for heat exchange and the clinker was still hot
at 300ºC after cooling.
Rotary kilns built from around 1916 through to 1926
used this type of cooler, but by the 1960s it had beenabandoned. Figure 4.9 shows a typical under-cooler.

4.3 Clinker Residual (Sensible) Heat Recovery:
Using Air Quenching Coolers2) 3)

Clinker coolers serve two main roles: “heat recovery”
from 1200-1300ºC red-hot clinker at the kiln outlet and“rapid cooling” of the red-hot clinker. Both functions
have a significant impact: “heat recovery” on the amountof fuel used and “rapid cooling” on the quality of thecement.
One reason for the poor thermal efficiency of rotarykilns is the heat loss from the clinker leaving the kiln at ahigh temperature, as discussed in 4.2.1. Various attempts

Fig. 4.9 Under-Cooler Fitted Under a Rotary Kiln (Top) 2)

4.3.3
Multi-Cylinder Coolers (Planetary Coolers) 9)
This cooling system used 10-15 cooling cylinders(1m-PĳP/ DWWDFKHGLQDSODQHWDU\PDQQHUDURXQG
the kiln outlet. The cooler rotated with the kiln; theclinker came into contact with the cool air in the coolingcylinders, with countercurrent heat exchange taking place.
Figure 4.10 shows a representative model planetary
History of Cement Manufacturing Technology

30cooler: the Unax cooler by FL Smith (Danish plant
manufacturer). The photograph shows the Unax cooler
attached to a large-scale SP kiln (6m diameter, 100m
length, 4,700t/d) built in 1972. A total of ten cylindricalcoolers are attached in a planetary manner.

Fig. 4.10 Unax Cooler (Chichibu Cement Kumagaya Plant)
10)

The first of this type of cooler in Japan was aremodeling by Asano Cement of a kiln at its Tokyo plant
into a Unax cooler kiln in 1927. Since this type achieved
better cooling results than the under-cooler type, most
new kilns built from then on (until the 1940s) usedplanetary coolers. Besides the Unax cooler, other types ofplanetary cooler included the Corpex type and the
Yogyosha type. All of these types of coolers were
designed to increase thermal efficiency by increasing thecontact area between the clinker and the air. This wasachieved by methods such as fitting chains or lifters
inside the cooler. These coolers offered the following
advantages:(1) High thermal efficiency could be achieved.
(2) The mechanisms were simpler and operation waseasier than the air quenching cooler (AQC) system
discussed in the following section.
(3) Since all of the cooled air was utilized as
secondary air for kiln burning, there was no needfor exhaust gas fans or dust collectors for coolers.
(4) Low power consumption.
However, the following drawbacks were also
identified:(1) Having a number of heavy cylinders were attachedto the hot part of the main kiln made it prone tothermal and mechanical strain, causing
breakdowns.
(2) Since all of the air was reused as secondary air, thesystem was susceptible to shortages of air foradequate cooling. If this happened, the clinker
tended to cool more gradually, which was not ideal
for cement quality. (Section (2) of 7.1.2 Clinker
Minerals discusses the relationship between
clinker cooling rate and cement quality.)

31(3) The output clinker temperature was 150-200ºC,
higher than the AQC system.
At the present time, almost all of these coolers havebeen phased out. The reason for this is that the NSP kilns,
which gained prevalence in the 1980s, were designedwith further improved thermal efficiency by utilizing theremaining gas as combustion air in the calcining furnace
after using it as secondary air in the kiln (see Chapter 5
for details).
4.3.4
Air Quenching Coolers (AQCs) 9)
This cooling system uses the idea of “crossflow heattransfer”, enabling more efficient heat transfer between
the red-hot clinker coming out of the rotary kiln and thecool air (atmosphere). The distinguishing characteristicsof this type of cooler are as follows.
(1) The clinker is cooled by air blown through a gratethat moves the clinker. Clinker of around 1300ºC
drops into the cooler from the rotary kiln and is
rapidly cooled as it comes into direct contact withthe air at atmospheric temperature. This results inhigh temperature secondary air, as well as
high-quality, rapidly-cooled clinker. The
temperature of the clinker coming out of the cooler
drops to around 100ºC.
(2) There is more air for cooling than needed forsecondary air. There have been various clever usesof the surplus heated air to help reduce the overall
heat used for cement production, such as fordrying raw materials (in the dry process). The
newest type of kiln, the NSP kiln discussed in
Chapter 5, has the capacity to utilize this surplus
heated air as secondary air for the calcining
furnace, thus helping to further improve thethermal efficiency of the NSP kiln.
Air quenching coolers (AQC) were first used in the
United States prior to the Second World War. Usage
spread throughout the West after the war. While an FL
Smith AQC at a Tokuyama Cement plant built in 1928 isregarded as the first use in Japan, usage did not become
widespread until 1951, after the Pacific War, when Nihon
Cement (formerly Asano Cement, now Taiheiyo Cement)
installed a Fuller-type AQC at its Nishitama plant. After
that, AQCs were used in new facilities, while also
gradually replacing the existing planetary coolers inexisting facilities. By the late 1980s, almost all cementkilns in Japan used AQCs 11).
There were several different types of AQCs, named
after the respective plant manufacturers that developed
them, including the Fuller type (USA), theAllis-Chalmers type (USA) and the FL Smith type, as
well as the Japanese Kawaju type (Kawasaki Heavy
Industries) and KY type (jointly developed by Yogyosha
and Kisha Seizo).

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

4.3.5Fuller Type Coolers 12) 13)
The Fuller type was the most suitable AQC forlarge-scale production. From the 1970s onwards, when
SP and NSP kilns were the predominant kilns being built,
all kilns were being fitted with this type of cooler. Somekilns built were capable of handling outputs of
8,000-9,000t/day. Figure 4.11 shows a schematic diagramof a Fuller type air quenching cooler.
Ongoing improvements have been made to Fuller type
coolers, although the basic design concept has notchanged significantly. One drawback with Fuller type
coolers is the phenomenon of red-hot clinker flowing
down on the floor of the grate, known as the “red river”
phenomenon. To prevent this, a number of structuralideas have been developed since the 1990s to ensure
long-term, continuous operation and improve heatrecovery efficiency by reducing the amount ofbreakdowns due to grate burnout.
One such idea that has even gained popularity in Japanis the “air beam” type clinker cooler, which has amechanism fitted to supply cooling air to the grate plate
units using a dedicated fan 12). The “air beam” system isused from where the clinker drops down to the secondary
air recovery area. This has improved the heat recovery
efficiency of the conventional system on a couple ofpercentage points.
There are several different types of air beam systems;by the year 2000, these had been adopted for use on
around 32% of kilns. The system is expected to continue
to spread in use as existing coolers are updated.

this period, focusing on the two main areas of heatrecovery, namely “rotary kiln exhaust gas heat utilization”
and “cooler exhaust gas heat utilization”, as well as otherefforts to reduce the amount of heat used.

4.5 Grinding and Separating (Classifying):

Capacity Increase in the Raw Materials
Process and Finishing Process

Section 4.2 above discussed how mass production
capability was achieved for kilns and coolers, that is, forthe burning process. However, in order for the central
process of burning to be capable of mass production, thepreceding and following raw materials process andfinishing process also need to increase in capacity
accordingly. The following sections outline thetechnological developments in crushing, grinding andseparating equipment used in the raw materials process
and finishing process from the late 1920s to 1960. Thesesections also provide a detailed discussion on the raw
materials process, including raw materials preparation,and the finishing process.
4.5.1
Crushing and Grinding 15)
The operation of crushing is very straightforward. The
use of quern-stones for crushing has been depicted in
frescoes from Ancient Egypt and Ancient Greece.
However, even with the industrial crushing or grinding
machines in the modern era of advanced technology, very
little of the input energy actually contributes to grinding(breaking down solid matter). With over 95% of theenergy supplied is lost, mainly in the form of heat thesemachines can be termed “energy wasting machines”. On
the opposite hand, the “grinding process” can also be
termed as an area in which there is a lot of scope forenergy conservation.

4.4 Trends in Thermal Efficiency Improvementfrom the Late 1920s to 1960

Table 4.5 shows the changes in overall amount of heatconsumption by types of manufacturing process during

Stationary grate plate
Secondary air

Blower

Chain curtain
Stack

Moving grate plate

Clinker crusher
Drive motor
Conveyor

Fig. 4.11 Fuller Type Air Quenching Cooler 14)
Table 4.5 Changes in Heat Consumption by Manufacturing Method 2)(unit 1,000 kcal/t-clinker)
Aug-Dec1940
Dry process

1,738
1,976
ņ
1,377
ņ

1954
1,716
1,941
ņ
1,424
ņ

1955
1,681
1,874
ņ
1,305
1,327

1956

1957

1958
1,581
1,823
1,400
1,012
957

Average
1,934
1,839
1,829
1,777
1,748
1,710
1,624
(Notes) 1. According to Cement Association survey.
2. For 1955 and 1956, the figures for wet process short kilns included those for long kilns as well.
3. Figures given in ( ) are in fuel oil units, l/t.

1,547

1,487

Lepol
Shaft

1,764
2,034
ņ
1,349
ņ

1953

1,616
1,819
1,442
1,095
1,107

Short
Long

1,772
2,041
ņ
1,381
ņ

1952

1,652
1,676
ņ
1,080
1,106

Wet process

1,891
2,089
ņ
1,300
ņ

1951

History of Cement Manufacturing Technology

32

The mill in the photograph is a raw materials mill (5.6m
diameter, 6,500kW). Finishing mills have essentially thesame exterior and interior. The photograph (1) anddiagram (2) in Figure 4.12 are from the late 1960s, whenmills were being made larger. The mills up until the late
1950s and early 1960s were mostly the same in style, but
far smaller in dimension. Figure 4.13 shows the upsizing
trend in finishing mills from the mid-1940s onwards after
the war, while Figure 4.14 shows photographs of (1)finishing mills installed in 1932 (2.47m diameter, 14m
long, 637kW) and (2) a raw materials mill installed in thelate 1950s (3m diameter, 10m long, 975kW).
(Note) “Cylpebs” were used as grinding media in thelater compartments of tube mills until around theend of the 1960s. Cylpebs were cylindrical piecesof steel 16-25mm in diameter and 16-35mm long.
They fell out of use as the use of small,abrasion-resistant balls became more widespread.
Since the use of cylpebs had little impact on later
technological developments, they are notdiscussed in detail in this report.

Airdischarge
Intake trunnion journal

Outlet trunnion journal

Partition blind plate

Ground powder(1) Exterior of a Tube Mill7)

(6,500kW)(2) Tube Mill Cross-Section

15)(3) Tube Mill Crushing
Diagram 1)

Mill power (kW)Fig. 4.12 Tube Mill

1950

1955

1960

1965

1970

1975

Year

Fig. 4.13 Finishing Mill Power Upscaling Trend 3)

33

Steel
balls

Partition
perforated plate
Raw material

Raw material

Hot air

Crushing machinery used in the cement industry
includes tube (ball) mills and vertical mills (roller mills).
Vertical mills are discussed in Chapter 5.
The tube mill was invented in 1892 by Meyer
Davidsen (Denmark). The first tube mill used in Japanwas imported from Germany by Asano Cement in 1899and used for grinding raw materials. It was powered bysteam (see Figure 3.3), as plants did not shift from steam
power to electric power until around 1912 (see 3.5, 4.2.2).
Although it is not known what the first tube mill was
like on the inside, the tube mills from the late 1920s
onwards were multiple-compartment mills with two to
five compartments on the inside, separated by perforated
partitions. The first compartments contained larger balls
for coarser crushing, while the later compartments
contained smaller balls for finer grinding. Many “opencircuit” tube mills, mentioned later, had three to fivecompartments, while many “closed circuit” mills had two
compartments.
Figure 4.12 shows (1) the exterior of a tube mill, (2) aninterior cross-section and (3) the balls and raw materials.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March(1) Finishing Mills Installed in 1932 (637kW)(2) Raw Materials Mill Installed in the Late 1950s (975kW)

Fig. 4.14 Example of Upsizing of Grinding Machinery (Mills) (Compared to Fig. 4.12 (1)) 7)

4.5.2

Dry Process Grinding (Raw Materials
Grinding) 15)
Raw materials grinding methods can be categorized bycement manufacturing method as “wet process grinding”
and “dry process grinding”, or by grinding process as“open circuit grinding” and “closed circuit grinding”, as
discussed later.
Grinding machinery for dry process grinding include“tube mills” and “vertical mills (roller mills)”. There are
two types of tube mills: (1) the “consecutive drying andgrinding type” and (2) the “simultaneous drying andgrinding type”. Type (1) tube mills have a drier fitted in
front of the grinding machinery. All vertical mills used inJapan have been the simultaneous drying and grinding
type since they were first imported. Up until the early
1960s, dry process raw material grinding was done on
tube mills with driers fitted in front. Chapter 5 discusses“simultaneous drying and grinding mills (air-swept mills)”
and “vertical mills”.
4.5.3

Wet Process Grinding (Raw Materials
Grinding)
By around 1975, the SP and NSP dry process methods
were being used for all cement manufacturing in Japan.
Before that, some companies were still using wet processkilns with “wet process grinding”. The raw materials
were fed into the tube mill together with water and theresulting slurry, which had around 35% moisture content,
was transported by pump.
Wet process grinding has the advantages of goodparticle dispersion and low power consumption. It also
has the benefit of the raw materials being more easily
homogenized in later processes. Due to these advantages,
the use of Japan’s first wet process kiln in 1929 made it
possible for Asano Cement to produce a very high-quality
high-early strength cement (see 4.2.3).
However, the rate of wear on the grinding media was
far greater compared to the dry process. Even with wet
process grinding, it was better in the following processes
for the slurry to have as little moisture content as possible.
In some cases, calcium lignosulfonate or other chemicals

were used as plasticizers to reduce the water content asmuch as possible while still being able to be transported
by pump.
4.5.4
Finish Grinding 3) 10)
In the Meiji Period (1868-1912), finish grinding wasdone using a fret mill (Figure. 3.4). Although tube mills
were first used by Asano Cement for raw materials
grinding in 1899, as mentioned previously, it is notclearly known when tube mills were first used for finish
grinding. However, from the circumstances outlined
below, it can be assumed that tube mills were adopted forfinish grinding soon after they were adopted for raw
materials and that they gradually grew more widespreadin use throughout the Taisho Period (1912-1926).
Chichibu Cement completed its Chichibu plant andcommenced operation in 1925. The finishing mill
installed at the new plant was a 7.32m long, 680kW,
two-compartment tube mill manufactured byAllis-Chalmers (USA), with a grinding capacity of 7.6t/d.
Records indicate that when the company later expanded
its facilities in 1927, the expansion included a 13m long,
three-compartment FL Smith mill with a grinding
capacity of 12.6t/d. It is therefore presumed that tube
mills were being used for all finish grinding by the late
1920s.
The finish grinding process at the time appears to havebeen mostly open circuit. It was not until the late 1950s
that closed circuit grinding was widely adopted into thefinishing process.

4.6 Separating / Open Circuit Grinding andClosed Circuit Grinding

12)“Separating” is the process of using certain
characteristic delineating values to separate solid particles
that are on a continuous scale of characteristic change. In
the cement industry, the delineating value is “particlesize”. The device used for separating is called a“separator (classifier)” and is discussed in 4.7 below.

History of Cement Manufacturing Technology

34

For dry process grinding, “dry process separating” iscarried out, using air as the separating medium. For wet
process grinding, there has often been no separatingprocess, partly because no coating forms on the surface ofthe balls inside the mill as they are constantly being
bathed in slurry, and partly because there are no suitable
wet process separators.
There are two grinding processes: “open circuit
grinding”, which involves only the grinding machinery,and “closed circuit grinding”, which involves a
combination of grinding machinery and a separator(Figure 4.15).

Coarse Separator
particles
Fine productRawmaterial

Grinding millOpen circuit grinding

ProductRawmaterial

Grinding mill

Closed circuit grinding

4.7.1
Gayco and Sturtevant Air Separators
Gayco air separators were first used in Japan in the
1910s, while Sturtevant air separators spread rapidly inuse from around 1955. The Gayco separator andsingle-axle Sturtevant separator were almost exactly thesame in their basic structure and operation, with the only
difference being the method of feeding in the raw
materials. The Gayco separator had a hollow verticalshaft to which the main blades, auxiliary blades anddistributor were attached; the raw materials dropped
through the shaft to the distributor. In the Sturtevant
separator, the raw materials were fed to the distributor
through a fixed chute on the outer rim of the central
vertical axis, which was not hollow. The single-axle
Sturtevant separator was an improved version of the
Gayco in terms of separating capability and maintenance.
Figure 4.16 shows a Gayco separator, while Figure
4.17 shows a Sturtevant separator.

Fig. 4.15 Open Circuit Grinding and Closed Circuit
Grinding 3)

Feed (F)Telescopic pipe

Open circuit grinding is the simplest method. The raw
materials are fed into one side of the mill and the finishedproduct comes out the other side. Consequently, although
the facilities are economical, it is difficult to adjust theparticle size of the product. By contrast, closed circuit
grinding separates the particles after grinding and thecoarser particles are sent back to the mill again. While
this has advantages, such as allowing a greater degree of
freedom in adjusting particle size and increasing grinding
capacity and efficiency by preventing over-grinding, thefacilities require a greater outlay and more space.

Main blade
Control valve
Auxiliary blades
Powder distributor

Guide vanes

PowderAir
Coarse powder (R)Fig. 416 Gayco Separator 16)

4.7 Separators (Air Separators, Classifiers) 16)
In closed circuit dry process grinding, grinding
efficiency and product quality rely heavily on theseparating capability of the separator.
The separator is a machine that separates solid particles
into different particle groups based on the fact that thebalance relationship between the external forces acting on
the particles, such as gravity and centrifugal force, andthe fluid resistance on the particles as they move throughliquid differs according to the size and density of theparticles.
Separators used in cement plants are categorized as “airseparators” because they use air as the separating medium.
Until the invention of the “eddy current separator” in
1979, the following three types of separators were used
for the raw materials process and the finishing process.
Each of these separators primarily used centrifugal force
for separating.
(1) Gayco air separators(2) Sturtevant air separators (single-axle, dual-axle)(3) Cyclone air separators
Chapter 5.5.4 discusses eddy current separators.

35

Fine powder (P)Feed (F)Main blade
Auxiliary blades

Controlvalve

Powderdistribution plate
Guide vanes(Open air)
air intake

Air outlet
To dust collector

Adjusting damper

PowderAir
Coarse powder (R)Fine powder (P)Fig. 4.17 Sturtevant Separator 16)

With the Gayco and single-axle Sturtevant separator,
the fineness of the powder could only be adjusted during
operation by increasing or decreasing the opening area on
the control valve. As a result, if it became impossible toadjust the fineness of the powder by adjusting the control
valve, due, for example, to significant variations in raw
material grindability, operations would have to stop andmeasures be taken, such as changing the number of

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchauxiliary blades. To achieve the necessary powder
fineness and separating efficiency, this would sometimes
have to be repeated ten or more times, which requiredconsiderable time and labor. Increasing the rotation of themain axle to increase the centrifugal force of the auxiliary
blades and make the powder finer would actually act tothe contrary by increasing the air flow of the main blade
attached to the main axle exponentially and thereby
increasing the updraft through the guide vanes, thus
reducing the effect of increasing the rotation of the mainaxle.
The dual-axle separator that emerged in 1972 rectified
the above flaw with the single-axle separator, allowing
the powder fineness to be adjusted by altering the rotationof the auxiliary blades without stopping operation. These
were developed in competition to the cyclone separators
discussed below, but were not widely used and a detailed
discussion is omitted here.
4.7.2
Cyclone Air Separators
Cyclone separators have six to eight cyclones mounted
around a central cylinder. Fans are mounted separately
and are connected by ducts. The basic separating
mechanism is not very different from that of the Gayco
and Sturtevant separators.
However, cyclone separators have the fan forcirculating air and the electric motor for dispersing
powder completely mechanically separate. This makes
adjustment during operation much easier and also makes
the machines suitable for upscaling. As a result, most new
separators built from the late 1960s onwards were cyclone
separators, both for the raw materials process and thefinishing process.
Figure 4.18 shows a cyclone separator.

The raw material is fed into the upper chute and is
distributed into the circulating ascending air current by
the centrifugal force of the distribution plate. The coarse
particles are affected more strongly by gravity andcentrifugal force and either drop down directly or lose
momentum on reaching the side wall and drop down to
the internal baffles. The circulating airflow through theguide vanes at the upper and lower levels acts again to lift
any fine particles mingled in with the coarse particles
back up with the circulating ascending air current, while
the coarse particles drop down as coarse powder.
When the fine powder is distributed into the air current,
it is lifted up by the ascending air current and subjected tothe separating action of the flange plate. Any coarse
particles mingled in with the fine particles are affected by
the centrifugal force of the flange plate, sending them tothe side wall, where they lose momentum and drop down.
With the coarse particles separated out, the fine particles
are lifted again to the exhaust duct, where cyclones
arranged in the direction of the airflow circulation
separate them out of the airflow and collect them as fine
powder. With the fine particles separated out by thecyclones, the circulating air is directed by the aircollection ducts on the upper part of the cyclone through a
fan into the central casing and is circulated back throughthe separator.
Cyclone separators were developed by German plant
manufacturer Wedag in 1962. Records indicate that they
were first introduced to Japan at the Chichibu Cement(now Taiheiyo Cement) No. 2 plant in 1966.

4.8 Raw Material Mixing and Storing Facilities:
The Emergence of Air Blending Silos Led to
Prevalence of the Dry Process3) 17)

Electric motor

Feed (F)Air
discharge

CycloneFlangeplate
Distribution
plate

Fan

Flap damper

Air slide
Guide vanes
Flap damper

Fine powder (P)Coarse powder (R)Fig. 4.18 Cyclone Separator 16)

Due to significant variation in raw material
composition, milled raw material powder (fines) cannot
be sent to the kiln as is, even if the feed into the mill isconstant. There needs to be blending machinery for the
raw material feedstock for the kiln to ensure as little
variation as possible.
Using the wet process, a homogenized raw mix can beachieved relatively simply with a slurry tank and slurrybasin. By contrast, it is very difficult to achieve ahomogenized raw mix with the dry process. For example,
even if the milled powder is distributed into small tanks,called mixing tanks, and poured out from three or fourtanks at the same time, it is difficult to keep composition
consistency within the permissible range.
Consequently, many cement companies used the wet
process (see 4.2.3) until the emergence of the “airblending” method, as the wet process was better forlarge-scale mixing of raw materials.
In 1934, Polysius (Germany) developed “air blending”

History of Cement Manufacturing Technology

36

a. Compressorb. Blending siloc. Dust collector

Fig. 4.19 Basic Configuration of an Air Blending System 17)

Several types of blending systems have been devised,with variations in diffuser layout and method of aeration.
The first system (batch type) used in Japan was by Aso
Cement in 1957, while the first use of a continuous
system was by Onoda Cement in 1959.
A typical Fuller (USA) continuous air blending system(Fuller Quadrant Blending) is shown below (Figure 4.20).

37

High pressure
Low pressuremachinery, making it possible to achieve homogeneous
mixing of dry process raw materials to the same level orbetter than the wet process. After that, companies
transitioned to the dry process, as it used less heat and theprocess was easy to upscale.
Air blending methods include batch blending andcontinuous blending. The batch method involves mixing
using multiple blending tanks in alternation. When thetarget composition range is achieved, the powder drops
into a storage silo. Powder mixtures that do not qualify
are rectified using separately-prepared powder
adjustments before dropping into the storage silo. In suchcases, the corrective calculations are relatively simple andcan be calculated manually.
Meanwhile, continuous blending involves collecting
and analyzing the milled powder at regular intervals andcalculating the corrective adjustments based on deviationfrom target values, then resetting the constant feed
weigher (CFW) to align with the target values. The
continuous method has demonstrated its true capabilities
from 1965 onwards, with the development ofcomputer-controlled continuous analysis equipment for
raw materials. After that, all blending silos have used thecontinuous method.
Figure 4.19 shows the basic configuration of an air
blending system. The basic structure of an air blending
silo is as follows.
(1) High-pressure air enters the silo through the“diffuser” attached to the base of the silo.
(2) The powder inside the silo is blown upwards andmixed (aerated).

Low pressure High pressure

Fig. 4.20 Fuller Air Blending Silo 17)

The base of this silo has a slight incline towards theoutlet. The entire base is fitted with aeration units(diffusers). The piping for the aeration units divides thebase of the silo into quarters, with each section having its
own air supply. This system is used for “cycling”. In
other words, once low-pressure air has been sent into theaeration units in one section of the silo to promote
aeration, high-pressure air is sent in, while low-pressure
air is sent into the other three sections. After a certain
amount of time has passed, the high-pressure air changes
to the next section, allowing all four sections to besupplied with high-pressure air in turn. In the section
being supplied with high-pressure air, the aerated powder
lifts up as it increases in capacity and goes above the levelof the other three sections being supplied with
low-pressure air. The powder in the high-pressure air
section then starts to flow into the low-pressure air
sections. Due to this cycling action, the powder isrepeatedly agitated as it changes height level and shifts inposition from left to right and top to bottom. The
transition usually takes 10 to 20 minutes; within 40
minutes to 2 hours, the powder has been completely
mixed. A device is used to supply the high-pressure air asperiodic pulsation rather than at a constant rate.
Air blending silos are another epoch-making
technological development in the history of cement
manufacturing technology. This equipment has made it
possible to achieve “homogeneity of kiln feedstock” withthe dry process that is equal to or better than that of thewet process. The wet process lost its dominance inproducing “superior homogeneity of raw materials andhigh quality of cement”. From 1965 onwards, all new
kilns built used the dry process, which was better forthermal efficiency and for upscaling. Now, no wet

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchprocess kilns are used to manufacture Portland cement inJapan.

4.9 7UHQGVLQ)XHO&RDOĺ)XHO2LOĺ&RDO

2) 4)

5)

The cement industry is a “fuel-intensive industry”. Foraround 90 years, the fuel used to manufacture cement inJapan was almost always coal, from the shaft kilns of the1870s right through to the 1960s. Given the scarcity ofJapan’s natural resources, the cement industry has been arare and valuable industry in that it has been capable ofsupplying all of its own raw materials and fueldomestically. When coal is used in regular combustion
furnaces, there is an issue with disposing of the ash;however, since the coal ash from cement kilns is used as araw material in cement, there is no problem disposing of
the ash, making coal a very convenient fuel source.
With several coal miner strikes in 1951-1952 making
coal harder to obtain, the cement industry took an interestin using fuel oil for burning. At the end of 1951, Ube
Industries started using fuel oil for burning, with othercompanies gradually following suit in switching fromcoal to fuel oil. However, with the deteriorating balanceof international payments leading to restrictions on oil
consumption in 1955 and the Suez Crisis in 1956, there
were growing concerns over the stability of the fuel oil
supply. Since fuel oil was also a little more expensive
than coal, the fuel oil trend abated for a while. Later, as
the demand grew for mass production of cement, thedemand for fuel also increased, while trade liberalization
caused the cost of oil to drop. As a result, the transition tofuel oil quickened in pace from 1960 onwards.
The 1973 oil crisis threatened the stability of the oil
supply and saw the price of fuel oil rise significantly. The
1979 oil crisis in the wake of the Iranian Revolution
threatened the oil supply once more and saw prices riseagain. The movement back to coal fuel spread rapidly
throughout the cement industry. Since the previous coalfacilities had already been scrapped and the domestic coalindustry had all but disappeared, coal burning resumed
using imported coal at new coal facilities that were
designed to be safer and more efficient. It is reported thatby the end of 1980, less than two short years after thesecond oil crisis, 72% of the entire industry had
transitioned to using coal.
Imported coal has remained the main fuel source forcement burning from that time to the present. Meanwhile,
active efforts have been made from the 1980s onwards touse waste products as fuel, including used tires, waste oil,waste plastic, waste wood and even city garbage. Chapter
9 discusses this in more detail.

4.10 The Beginnings of2)Diversification of theTypes of Cement

Japan’s first Portland cement was produced at the
government-managed cement plant in Fukagawa, Tokyoin 1873. This marks the beginning of “ordinary Portland
cement” in Japan.
The rest of the Meiji Period through to the 1910s wasdevoted to making improvements to this Portland cement
and to the methods used to manufacture it. Accordingly,
there was no product diversification during this time.
Product diversification eventually began with the aim offurther enhancing the characteristics and functions of“ordinary” cement. Most diversification went in one of
the following two directions.
(1) Achieving the aim through the preparation of thePortland cement, such as by adjusting the chemicalcomposition.
(2) Achieving the aim by adding other mixtures to thePortland cement (blended cement).
Chapter 8 discusses these diversified types of cement
in more detail. This section discusses the course ofdiversification and differentiation from its origins in the
1910s.
Onoda Cement manufactured Japan’s first “blended
cement” in 1900, for building the dock at the Sasebo
Naval Station. To make this blended cement chemicallyresistant, it was blended with volcanic ash at a 3:1 ratio(ratio by weight). This was the original blended cement,
aiming to produce the same effect as the slag cement andsilica cement that were to emerge later. (Chapter 8
discusses blended cement and the quality improvements
made to it.)
In 1913, Yawata Iron Works manufactured “slagcement” blended with blast furnace slag. This was an
attempt to effectively utilize the slag produced from blast
furnaces in the manufacturing of pig iron. It was also an
attempt to improve ordinary Portland cement, as Onoda
Cement had done with volcanic ash blended cement.
Onoda Cement began manufacturing “white Portland
cement” in 1916, catching the attention of thearchitectural world. Production of this white cement hascontinued to the present day, with gradual improvements
in quality. Not only is it used for sculptures and cement
coatings, it is also completely suitable to be used instructural concrete.
With the applications for concrete increasing and its
fields of use expanding in scope from the late 1920s
onwards, there was growing demand from customers for
cement that could meet different needs. Meanwhile, thecement industry brought out several kinds of new
manufacturing facilities in succession, as mentioned
previously, and made advancements in chemical research
related to cement (details in Chapter 7). The industry
grew in its capacity to meet various customer demands
and the types of cement began to diversify as a result. In
1929, Asano Cement started manufacturing “high-early
History of Cement Manufacturing Technology

38strength Portland cement” and marketed it under the nameof “high-performance cement” or “Asano Velo Cement”.
Other companies followed suit and began manufacturing
similar cement, naming their products as “refined” or“high-performance” cement. All of these were improved
products characterized by the early development of highstrength.
In 1934, Asano Cement successfully manufactured
low-heat and moderate-heat Portland cement and starting
marketing these under the name of “Asano Mascon
Cement”. With some innovation in the chemicalcomposition of the cement, the product had a low
hydration heat rate (see 7.3) and was used forconstructing dams and other such projects.
Chapter 8 discusses the diversification of Portland
cements in more detail, including the “white cement”,“high-early strength cement” and “moderate-heat cement”
mentioned above.
The manufacturing of various different “blended
cements” gained traction from the late 1920s onwards.
Asano Cement returned to manufacturing blast furnace
slag cement, mentioned above, in affiliation with Tsurumi
Iron Works (now DC). Around 1935-1937, a number ofcompanies started manufacturing silica cement andmarketing it under different names, such as silica cement
or silicate cement. As all of these had added chemical
resistance, like blast furnace slag cement, they weremainly used for constructing levees.
The Pacific War was a major obstacle to diversification.
It became impossible to manufacture high-early strength
cement, moderate-heat cement and otherhigh-performance cements due to shortages of goodquality coal and other materials needed for manufacturing.
Meanwhile, production of blast furnace slag cement andsilica cement increased, as these required fewer resources.
For a while, production of these cements accounted for
one third of all cement production. Cement usage had to
be rationalized; low-strength, non-structural cements werealso being produced, such as all-purpose cement andplastering cement.
After the war, cement restrictions were lifted in 1950
and freedom of manufacturing and marketing wasreinstated, accompanied by a revival of high-earlystrength cement and moderate-heat cement manufacturing.
Since then, advances in cement chemistry and modern
manufacturing facilities have enabled the continuing
diversification of cement products with different
functions. Chapter 8 discusses the modern diversity of
cement products in more detail. At the present time, 68%of the cement on the market is “ordinary Portland
cement”. Combined with high-early strength,
moderate-heat, low-heat and sulfate resistant cement, “allPortland cement” accounts for around 75%, while“blended cement”, including blast furnace slag cement,
accounts for around 25% 18).

39

4.11 &HPHQW3ODQW3ROOXWLRQ,VVXHVĺ
Installation of Dust Collectors

With manufacturing machinery at cement plants
including crushers, grinding mills, kilns (rotary or shaft)and fans, the inevitable challenge is dealing with dust,
particulate matter (see Note 3), noise and other pollution
and environmental issues.
4.11.1 Pollution Issues 4) 6)
The first cement company in Japan to incur a serious
pollution issue with local residents was Asano Cement’s
Fukagawa plant (Tokyo). This is outlined in the following
summary of excerpts from 100-Year History of Nihon
Cement 4).
Around 1885, residents of Fukagawa voiced theirconcerns over ash fall from the cement plant. The
Superintendent-General of the Metropolitan Police
DXWKRU¶VQRWHWKLVZDV6DGDNL\RƿVDNRXQWLO
December 1885, then Michitsune Mishima) enlisted
7DWVX]ǀ6RQHDVVRFLDWHSURIHVVRUDWWKH,PSHULDO
College of Engineering and assistant engineer for the
Metropolitan Police, to investigate ways to eliminate
smoke pollution from the Asano plant. In the end,
6DEXUǀ8WVXQRPL\D¶V DXWKRU¶VQRWHVHH DVVHUWLRQ
that particulate matter is unavoidable and harmless tohumans and the persuasive efforts of the authorities on
the residents meant no major social issue arose fromthe Asano plant ash fall at that time. Later, the ash fall
was reduced by shaping the raw materials into bricks
for feeding into the shaft kiln and the issue appeared tobe resolved for the time being.
In 1903, the Fukagawa plant became the first plantin Japan to use a rotary kiln, leading to a major
revolution in manufacturing methods. Signs began toappear that the ash fall issue would recur. This was not
such an issue when the rotary kiln was first introduced,
as at first the ordinary raw limestone burning process
was being used. However, as the process transitioned
to the calcined lime burning process, the number ofrotary kilns in use steadily increased. When production
volumes surged, enabled by continuous burning, theamount of ash being dispersed outside of plant sites
also increased.
The issue resurfaced around 1907. The Fukagawa
Youth Association was formed in the vicinity of theplant, lodging petitions to the authorities and staging
protests against the company. The antagonism between
the company and the residents grew volatile around1910-1911. With mediation from the authorities, thecompany promised the residents in March 1911 that it
would close the Fukagawa plant within five years (bythe end of 1916). Substitute land was selected in
Kawasaki, but although fast progress was made on theconstruction of the new facility, the outbreak of theFirst World War made it difficult to obtain materials
and caused delays in the delivery of the machinery that
had been ordered. With consent from the residents, thetimeframe for closing the Fukagawa plant was
extended for one more year.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchDespite the acceptance of the one-year extension,
the closure of the Fukagawa plant was inevitable.
However, as luck would have it, news arrived at thatexact time that the Cottrell electrostatic precipitator had
been a success in the United States. The Cottrell
electrostatic precipitation method was a method
devised by American chemist Fredrick Gardner
Cottrell of applying a principle invented in Germany in1824 to a plant facility.
In 1916, Asano Cement decided to directly purchasethe patent rights and all of the machinery from theUnited States. The precipitator machinery arrived in
1917 and the installation was completed with someround-the-clock work under the supervision ofAmerican engineers. By the end of the year, four rotarykilns were confirmed to have fully functioning dust
collectors. The Fukagawa Youth Association andresident representatives met with the company
president and other company executives and agreed
that the precipitators were extremely effective. They
finally withdrew their appeal to close the plant. The
Fukagawa plant ash fall issue was resolved amicably.
The above is a summary of a passage on the Fukagawa
plant ash fall issue in 100-Year History of Nihon Cement.
This incident was the first introduction of a Cottrell dust
collector (see 4.11.3) at a cement plant in Japan. After
that, the use of electrostatic precipitators at cement plants
spread throughout the country. Records indicate that thefirst use of a Cottrell device by Onoda Cement was at the
Atetsu plant in Okayama in 1933 and the first use by
Iwaki Cement (now Sumitomo Osaka Cement) was at the
Yotsukura plant in Fukushima in 1927, while Chichibu
Cement began using it in 1925.
4.11.2

Establishing and Tightening Environmental
Laws and Regulations
Up until around the mid-1960s, cement plant
environmental and pollution issues were mainly tangible,
such as particulate matter, dust and noise. Policies for this“pollution” involved reducing or suppressing thecontaminant, such as through the use of dust collectors
and soundproofing. Most plants carried out operations
without any major issues with local residents. However,this does not mean that cement plants were emitting zeroparticulate matter, dust or noise, but rather that the sightof the roofs of neighboring houses white from years ofdust buildup was “the usual view”. Local residents
resigned themselves to the sight as “unavoidable, because
the plant provides jobs”. Japan’s first law on air pollution
was the Act Concerning Regulation of Soot and Smoke
Emissions (or the Smoke and Soot Regulation Law),
enacted in 1962. Before that, situations such as the one
described above were not in violation of the law.
The Air Pollution Control Act was created in 1968 andunderwent significant amendment in 1970 at the 64th Diet

session, otherwise known as the “Pollution Diet”, alongwith the creation of the Noise Regulation Act. Cement
plants had to take strict pollution control measures.
Through these laws and later amendments, people began
to understand “environmental regulation” in the broadest
legal sense, that it covers more than tangible pollution andincludes nitrogen oxide emissions, sulfur oxide emissions
and heavy metals in the cement. These are discussed in
Chapter 6.
Below is a brief discussion of the two main dust
collectors used at cement plants.
4.11.3 Electrostatic Precipitators 19)
Typified by the Cottrell precipitator (Figure 4.21)
mentioned previously, there are several different models
of electrostatic precipitator from different manufacturers,
but the fundamental principle is the same.

Fig. 4.21 Cottrell Precipitator 7)

The underlying principle for electrostatic precipitators
is to pass exhaust gas through an electrical field that is
generated between a discharge electrode and a dust
collecting electrode. Negative ions generated by a cathodecorona adhere to and electrify particles in the exhaust gas.
The electrified particles are separated and collected at the
dust collecting electrode through the effect of theelectrical field.
The main advantages of electrostatic precipitators
include: (1) high dust collection rate (over 90%); (2) low
pressure loss (10-20mmAq); (3) low power consumption;(4) ease of maintenance; and (5) ability to handle hot gas.
Disadvantages include: (1) high setup costs; (2) large
facility footprint; and (3) depending on its composition,
exhaust gas can cause corrosion or impede dust collection
performance. Given these advantages and disadvantages,
these precipitators have mainly been used for processing
exhaust gas from kilns and clinker coolers used in themain burning process at cement plants. However, mainly
due to disadvantage (3) above, the use of bag filters has
become more widespread for processing kiln exhaust gas

History of Cement Manufacturing Technology

40since the 2000s.
4.11.4 Bag Filters 19)
Besides electrostatic precipitators, bag filters are also
widely used for dust collectors at cement plants. The
underlying principle for bag filters is the same as for thebag filters used in household vacuum cleaners. Although
they can be used at smaller facilities, are suitable fordirected dust collection and have high dust collection
efficiency, they cannot be used for high-temperature or
high-humidity gas due to the fiber bag used. They havemainly been used for collecting dust from crushing andgrinding systems and transporting systems.
In the 2000s, large quantities of different kinds ofrecycled resources began to be used for fuel and raw
materials. For the conventional electrostatic (Cottrell)
precipitators used in cement kiln exhaust gas processing,
this caused operating instability, deterioration and otherproblems. Meanwhile, advances in burning technology
and waste heat utilization lowered the temperature of kiln
exhaust gas and made it more stable, while advances inheat-resistant fibers improved the heat resistance of bag
filters. Accordingly, bag filters began to be used for kiln
exhaust gas dust collectors as well (see 6.1.3).

4.12 Trends in Cement Delivery Format:%DUUHOVĺ%DJVĺ%XONĺ&HPHQW
4) 5) 10)Distribution Revolution
In the early days of the cement industry in the late
1800s and early 1900s, all cement was freighted fromfactories in barrels. Jute sacks began to be used from the
1910s, followed by paper sacks from the mid-1920s.
Barrels and jute sacks were no longer used by around
1940.
The Meiji-era barreled cement was mainly delivered tocustomers by wagon or boat. While trucks and railroads
replaced wagons in the 1910s and jute and paper sacks
replaced barrels, the delivery method of “transporting
packaged cement” changed very little for around 80 years,
until the mid-1950s.
In 1936, Ube Industries started transporting cement inbulk, using Japan’s first cement tanker (a special shipwith facilities for loading and unloading bulk cement).
Transporting in bulk means transporting the cement
powder without packing it in bags or other containers.
However, there was no major shift to bulk transportationin the overall industry for another 20 years. It was not
until around 1954 that companies started rapidly adopting
bulk transportation of cement by railcar, truck or ship. At
the present time, 97% of all cement transported from
cement plants is transported in bulk.

41

The following sections discuss the trends in cement
delivery format and the significant impact of bulk
transportation on the overall cement industry.
4.12.1 From Barrels to Jute Sacks
The idea of using barrels as product packaging in theearly days of the cement industry was imported from theWest along with cement manufacturing technology.
Traditional Japanese barrels come in the form of a bucket
and lid, such as those still used today for sake, miso andsoy sauce. By contrast, the barrels used for cement were“Western style” barrels (the same as those used forwhiskey and beer, see Figure 2.10). Consequently, theearly barrels were made by bucket makers. They weremade from slats of Japanese cedar encircled with bamboo
rings and were filled with cement by hand. Records from
Onoda Cement indicate that a barrel-making machine wasintroduced in 1894, a decade after the industry began, andthat barrel-filling machinery was being used by around1897 at the latest. The unit of weight used for cement
trading was set as the “pound” atgovernment-administered plants in 1880.
When Onoda Cement and Asano Cement were
established (1883), one barrel was 400 pounds (181 kg).
In January 1901, the weight of one barrel wasstandardized across the industry as 380 pounds (172 kg).
However, since it was transported by wagon or by foot, it
was also sold in half-barrels and quarter-barrels,
depending on the needs of the customer. Although thewooden barrels were sealed and could also conveniently
be transported by rolling, there were some challenges
with them, such as if the wood had not been properly
dried, it could shrink and allow the contents to leak out,
or if large numbers of barrels were needed, it was difficult
to prepare the timber.
In 1898, Onoda Cement trialed Japan’s firsttransportation of cement in jute sacks (152 pounds; 69 kg).
The sacks were not standardized and were mostly reusedsugar, fertilizer or flour sacks. Transportation in sacks
progressed no further than being a secondary usage until
the 1910s. In 1911, the company standardized a“one-third sack” (127 pounds or 58 kg was one-third of abarrel). After that, jute sacks of this size began to be more
widely used.
Jute sacks expanded in use in 1914, as the soaring priceof timber from the outbreak of the First World War madeit difficult to manufacture barrels. In 1921, there were twosizes of jute cement sacks, 127 pounds (58 kg) and 95
pounds (quarter-barrel, 43 kg). The metric system wasadopted in 1924, with the cement industry defining the
net weight of one jute sack as 50 kg and one barrel as 170
kg.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

4.12.2

From Barrels and Jute Sacks to Paper
Sacks
Although it was standard practice to retrieve barrels
and jute sacks from customers after use, this of course
cost time and money. Consequently, cement companies
started using “throwaway” paper sacks from around
1926-1927.
The first company in Japan to use paper sacks isthought to have been Chichibu Cement when it began
operations in 1925. When the company ordered a paper
sack filling machine from the United States for a newplant, the order came with 4,000 paper sacks. These sacks
were made from four layers of kraft paper; this type wasused until the late 1930s 10). Accordingly, paper sackfilling machines (packers) have been used for packaging
cement into paper sacks (bagging) since the use of paper
sacks was first introduced. The operator loads the cement
into the packer and the cement fills the sack automatically.
When the bag reaches the designated weight, the cement
feed stops automatically and the sack drops onto atransporting conveyor (Figure 4.22).

Fig. 4.22 Paper Sack Filling Machine (Packer) 7)

The net weight of a paper cement sack remained at 50
kg for the first 50 years. This was later changed due todemand from the plastering industry and other users,
down to 40 kg in 1971 and down again to 25 kg in 1996.
During the three decades from the adoption of paper
sacks in the late 1920s to the widespread adoption of bulk
transportation, discussed below, more than 90% of all
cement orders from plants were delivered in paper sacks.
While paper sacks are still used for transporting cement
today, the amount of cement sold in paper sacks is now aslittle as 3% of all cement.
4.12.3

From Paper Sacks to Bulk Cement:“Distribution Revolution” in the Cement
Industry
In the late 1950s, the delivery of cement from cement
plants suddenly changed from paper sacks totransportation in bulk. This transition to bulk
transportation in the delivery and distribution of cement
was more than just a change in delivery format. It was amajor revolution in cement distribution and a significant
factor in reforming the structure of the entire cement
industry (details in Chapter 5).
The three main reasons cement companies were drawn
to bulk transportation are as follows.
(1) Cement companies working to reduce theirtransportation costs(2) Increasingly widespread use of ready-mixed
concrete (see Note 4) at construction sites(3) Growth of the concrete products industry
Since reducing transportation costs by transporting
cement in bulk was an advantage for the customer as well,customers rapidly adopted bulk transportation andactively began to improve their facilities and take othersteps to handle bulk cement.
(1) Bulk Transportation to Reduce Transportation
Costs 2)
As a product, cement has the distinguishing
characteristics of (1) being heavy and bulky, (2) not
lasting long in storage and (3) having a poor
value-to-effort rate. Since most cement plants in Japan arelocated near sources of raw materials, transporting cement
to metropolitan areas where it is needed can be quite
costly. As a result, the cost of distribution makes up alarge proportion of the sales price of cement. It has been asignificant challenge for cement companies to try to
reduce transportation costs by devising improved andmore rationalized means and methods of transportation.
Before the war, railcar and ship each accounted for
40% of cement transportation, with the remaining 20%
carried by truck or other modes of transport. However,with a shortage of ships after the war making shiptransportation more expensive, there was a rapid increasein the amount of cement transported by freight car. By
1945, 63% was transported by railroad, 20% by ship and
17% by other means. In 1952-1953, during the Korean
War, there was a rapid increase in freight transportation
due to a rise in domestic industry, putting pressure onland and sea transport. The economic boom in 1957 led tofurther difficulties with transportation. Rising rail freight
prices led to a surge in sea freight prices, resulting in avery poor transportation situation.
The bulk cement transportation system emerged tobreak this deadlock. Cement companies streamlined
transportation by setting up their own bulk transportation
facilities and managing their own cement transportation.
The bulk cement distribution channels were as follows:(1) Coastal cement plants

History of Cement Manufacturing Technology

42

&HPHQWSODQWĺFHPHQWWDQNHUĺVHUYLFHVWDWLRQ
66 ĺEXONWUXFNĺFXVWRPHU UHDG\-mixed
concrete plant, concrete products plant, dam orother major construction site)(2) Inland cement plants&HPHQWSODQWĺEXONWUXFNĺFXVWRPHU
Many coastal cement plants were in areas of Hokkaido,
Chugoku, Shikoku and Kyushu that were far away frommajor cities. Cement was initially transported by tanker
ship to service stations (SS) in major consumer areas in
the Tokyo, Nagoya and Kansai regions. By contrast,
many inland cement plants were located near major
consumer areas and the cement was often transported
directly from the plant to the customer by bulk
transportation truck. The distribution for cement powder
came to be similar to that of liquid petroleum products.
Figure 4.23 shows a bulk transportation truck being
loaded with cement.

Fig. 4.23 Cement Being Loaded onto a Bulk Transportation(2) Widespread Use of Ready-Mixed Concrete at
Construction Sites 4)
Regardless of the advantages given in (1) above, the“packaged product” handling and distribution formatchanged very little in the first 80 years of Japan’s cement
industry because of the concrete construction method of“mixing concrete at the construction site”, that is, “mixing
cement, gravel, sand and water on site” did not change.
The major change to this situation came with theintroduction and popularization of ready-mixed concrete.
The concrete was not mixed at the construction site, but
measured and combined at the ready-mixed concrete
plant and then mixed in the truck (concrete mixer truck)
while being transported to the site. Thus began a dramaticchange in concrete construction, with the fluid concrete
only poured into the formwork at the construction site.
While the use of ready-mixed concrete had spreadthroughout the United States before the Second World
War, the first ready-mixed concrete plant in Japan was
built in 1949 at Narihira-bashi, Tokyo, by Tokyo
Concrete (a subsidiary of Iwaki Cement, now Sumitomo
Osaka Cement) 20). It became more widely used over the
next while, mainly in urban areas, until around 1961,
when the number of ready-mixed concrete plants rapidly
increased. In 1967, there were 1,067 plants in the country;
five years later in 1972, there were 2,936. Five years afterthat in 1977, there were 4,808, increasing nearly fivetimes over in ten years and spreading right throughout thecountry.
Almost all cement delivered to ready-mixed concrete
plants was transported by truck in bulk.

Truck 7)The main outcomes achieved by rationalizing cement
distribution through bulk transportation are as follows.
(1) Transportation mobility
Bulk transportation allows all handling to bemechanized, taking far less time than loading andunloading packaged product. Loading andunloading can also be done in the rain without any
problem. Since the ships, railcars and trucks are allowned or operated by the company, transportation
can be very flexible.
(1) Reduced transportation costs
With simpler and faster handling as mentioned
above, the handling costs are also cheaper. Thereis also far less product loss during transportation
than with packaged product. A relative drop in thecost of sea transport compared to land transport(railcar, truck) has meant that remote coastal plants
can compete fairly with inland plants in suburban
areas.

43(3) Growth of the Concrete Products Industry
Concrete products produced at plants today are used inevery corner of society. While some of this diverse rangeof concrete products took shape in the West and havebeen produced in Japan since before the war, theproliferation of concrete products we see today did notcome about until after the Pacific War. The range ofdemand grew during postwar reconstruction, while theeconomic boom from the late 1950s ushered in an era of
expansion in every direction in the concrete products
industry, from highways and the bullet train to seweragedevelopment and apartment buildings.
Up until the early 1950s, concrete products plants were
small in scale and had cement transported in sacks. Fromthe late 1950s onwards, it was transported by trucks inbulk.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

(4) Summary of the Transition to Bulk
Transportation
From the postwar reconstruction period to theeconomic boom, cement transitioned to bulk
transportation due to three phenomena occurring almost
simultaneously, as mentioned above: (1) a shift to bulk
transportation handling and distribution facilities toreduce transportation costs; (2) advances in ready-mixed
concrete; and (3) growth of the concrete products industry.
In 1951, the amount of cement transported in bulk
accounted for 6% of all cement transported. Seven years
later in 1958, this figure had risen to 25%. By around1980, over 90% of all cement was transported in bulk.
Today, 97% of all cement transported from cement plants
is transported in bulk.
Although it goes without saying that the economic
benefit was the greatest incentive for the bulk cementtransportation system mentioned above, it must also be
remembered that it was undergirded by technologicaladvances in transportation and storage facilities to be able
to transport powder in bulk. However, many of thesefacilities and devices lay beyond the walls of cement
plants, shown in Figure 1.3, and many were used in otherpowder industries as well. Accordingly, detailed
descriptions have been left out of this report, which
focuses on “cement manufacturing technologies incement plants”.
As at 2013, around 72% of cement orders are forready-mixed concrete and around 13% are for concrete
products, with the remaining 15% going to other uses 18).
Note 1: Primary and secondary air
The air that is blown into the kiln from the burner together withthe fuel is called primary air, while the air that travels into thekiln from other vents than the burner to supplement primary air
is called secondary air. In cement burning, secondary air is the
air used to cool the hot clinker in the cooler.
Note 2: Oil (Petroleum) Coke
A solid residue of mostly carbon, obtained by pyrolysis of
vacuum residual oil or other heavy petroleum oil in a coker.
Note 3: Dust and particulate matter
Defined as follows in the Air Pollution Control Act.
Dust: Soot and dust generated by the combustion of fuel or by
the use of electricity as a heat source (in other words, soot).
Particulate matter: any substance generated or dispersed as aresult of crushing or sorting materials or any other mechanicalprocess, or as a result of the accumulation of such materials.
Note 4: Ready-mixed concrete
Concrete with cement, gravel, sand and water measured andmixed but not yet set. Also called fresh concrete. Plants that
manufacture ready-mixed concrete are called “ready-mixed
concrete plants”, while the trucks that transport the concrete
from the plant to the construction site are called “ready-mixed
concrete trucks” or “mixer trucks”.
Note 5: Concrete products
Concrete products are products made of concrete that are cast or
produced at a plant and transported to the construction site,rather than being poured into formwork at the site. There arevarious different kinds of concrete products, including
U-channel blocks, blocks for walls, paving blocks, concrete
walls for homes and other buildings, sewer pipes, utility poles,
river revetments, road and rail bridge girders and tunnel walls.

References (all in Japanese)
1) Sutezo Sugishita, Cement Industry in Japan, Poplar
Publishing, 1962.
2) Minoru Fujita, Cement, Yuhikaku Publishing, 1960.
3) Tatsuo Okabe, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 41-51,1978.
4) Nihon Cement Co., Ltd., 100-Year History of Nihon
Cement, 1983.
5) Onoda Cement Co., Ltd., 100-Year History of Onoda
Cement, 1981.
6) Takashi Ueno, Supplement to the History of Cement
Technology, Onoda Cement, 1980.
7) Supplied by Taiheiyo Cement Corporation.
8) Nikkan Kogyo Shimbun, “A Success Story: Onoda
Cement”, 1962.
9) Toshikazu Ichiyanagi, Ikuo Isobe, Kanzaburo Sutoand Harada Hiroshi, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 144-152, 1978.
10) Chichibu Cement Co., Ltd., 50-Year History of
Chichibu Cement, 1974.
11) Japan Cement Association, “Examination of Air
Quenching Coolers”, Report T-2 of Committee on
Fuel, 1955.
12) Japan Cement Association, “Technologies of Energy
Saving and Resources Saving in the Japanese Cement
Industry”, Report T-22 of Committee on cement
manufacturing Technology, 2002.
13) Akira Mochizuki, “Present Status and Future Outlookof Clinker Coolers”, The Cement Manufacturing
Technology Symposium, No.34, pp.71-84, 1977.
14) Japan Cement Association, “Examination of Rotary
Kiln Coolers”, Report T-11 of Committee on Fuel,
1974.
15) Toshikazu Ichiyanagi, Atsutoshi Kurotaki andTamotsu Negishi, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon, Vol.
4: Manufacturing Technology”, pp. 96-111,1978.
16) Minoru Ushiki and Atsutoshi Kurotaki, Chichibu
Cement (now Taiheiyo Cement) company document“Cement Dokuhon Vol. 4: Manufacturing
Technology”, pp. 111-118,1978.
17) Mitsuru Saito, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 118-125,1978.
18) Cement Yearbook 2014, Cement Press, 2014.
19) Takashi Kato and Koichi Kaneko, Chichibu Cement(now Taiheiyo Cement) company document “Cement
Dokuhon Vol. 4: Manufacturing Technology”, pp.
218-229,1978.
20) Sumitomo Cement Co., Ltd., 80-Year History of
Sumitomo Cement, 1987.

History of Cement Manufacturing Technology

44

5

The Development of Japanese Cement
Manufacturing Technology (1960­ ) 1) 2) 3) 4)

For the two decades from the early 1960s to around1980s, the Japanese economy maintained its rapid growth,rebounding from the two oil crises that took place duringthat time. In 1960, cement production volumes werearound 22 million tons. By 1979, they had reached an
unprecedented peak of around 88 million tons (83 million
tons for the domestic market). Although the demand for
cement later dropped off as the Japanese economy went
into a period of low growth, the Great Hanshin
Earthquake of 1995 and exports to Asia prompted a
temporary rise in the market. In 1996, production
volumes reached just less than 100 million tons (82.4
million tons domestic). However, the downward trend
continued after that, with volumes dropping to 61 million
tons (45 million tons domestic) by 2014, around 60% of
the 1996 figure, despite some demand for rebuilding after
WKH7ǀKRNX(DUWKTXDNH)LJXUHVKRZVWKHWUHQGV
in domestic cement demand.
With the cement industry trenGLQJIURPKLJKJURZWKĺORZJURZWKĺVKULQNLQJPDUNHWWKHIROORZLQJdevelopment trends were observed in cement
manufacturing technology.
(1) Ongoing enlargement of manufacturing facilities
during high growth(2) Focused efforts on energy-saving technology to
reduce costs during low growth(3) Focus for technology development shifted tocontributing to a resource-recycling society in theface of a shrinking market

The trends in cement-related technology from the
1960s onwards can be broadly categorized as follows.
(1) Upscaling of cement kilns
As kilns grew in size, the machinery and equipment
for the raw materials process, the finishing process
and the shipping process also had to grow in size.
Since upscaling required significant investment,“priority investment plants” were selected in terms of
the size of limestone deposits and access to major
cement markets.
(2) In the process of upscaling, the superiority of thesuspension preheater kiln (SP kiln) over dry processkilns with attached boilers, wet process kilns, Lepol
kilns and other existing types became apparent.
(3) Following on from (2) above, development began on
the new suspension preheater kiln (NSP) as an
improvement to the SP kiln. The NSP method wasestablished as world-leading Japanese cement
manufacturing technology.
(4) Following the two oil crises of the 1970s, the goal
was to conserve energy with all machinery andequipment at cement plants. The superiority of NSP
kilns and vertical mills became apparent, while Japantechnology continued to contribute to major energy
savings in grinding machinery with eddy current
separators (such as the O-SEPA), vertical mill
pre-crushers (such as the CKP) and vertical cement
mills (such as the OK mill). Waste heat power
generation also became widespread, using up as
much heat as possible from kilns and coolers. As aresult, the Japanese cement industry ranked top in theworld for energy conservation.

10,000 tons

Bubble burst

Bubble economy

1979 oil crisis

1973 oil crisis

Archipelago
remodeling boom

1965-1970
Izanagi boom

Tokyo Olympics
boom

1958-1961 boom

1950s boom

Year

Fig. 5.1 Trends in Domestic Cement Demand (1950-2011) 1)

45

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March5.1 Suspension Preheater Kilns (SP Kilns) 1) 5) 6)
The two decades from the 1960s to the 1980s were atime of constantly-increasing domestic demand for
cement, as well as increasingly stricter enforcement ofenvironmental regulations. In this business environment,
cement kilns had to: (1) have good thermal efficiency; (2)have greater kiln output; (3) be capable of long-term
stable operation; (4) produce high quality clinker; and (5)have a low pollution factor.
SP kilns and the improved NSP kilns, discussed later,
proved to be superior to conventional kilns in these

aspects. Daiichi Cement (now DC in Kawasaki,
Kanagawa) started operating Japan’s first SP kiln in 1963.
From then until the development of the NSP kiln in the
mid-1970s, most new kilns built were SP kilns.
Table 5.1 shows the heat consumption, output percapacity and maximum capacity for the different types ofkilns in use in 1975.
Table 5.1 Heat Consumption, Output per Capacity andMaximum Capacity by Kiln Type 5)
Heatconsumption(Ht)kcal/kgcl’

Kiln TypeDry

Attached boiler (DB)Wet

(5) Throughout the entire course of (1) to (4) above,
developments were being made in computerized
control of processes. This made processes morestable and improved product quality.
(6) Environmental regulations were enacted in the 1970s
and the cement industry had to comply with strict
enforcement. Full use of existing technology and newtechnological developments made it possible to meetthe strict controls.
(7) Global warming became a topic of attention from the
1990s onwards. Since the cement industry caused
carbon dioxide emissions by burning fuel anddecarbonizing limestone, efforts were madeinternationally to research countermeasures.
(8) From the 1960s onwards, major advances have been
made in instrument analyzers, electron microscopes
and X-ray analyzers. This has made it possible toknow about the minerals and hydrates in cement inmuch more detail. Based on this knowledge,
successive “functional” cements have beendeveloped.
(9) Amidst efforts towards conservation of energy andresources to preserve the global environment, ideas
have come forward about new initiatives for using
waste materials in cement manufacturing.
(10) With the demand for cement dropping since the late
1990s, ventures for disposing of industrial andmunicipal waste have provided a significant income
source. In order to expand their waste recycling
operations, developers have gone for technology thatcan dispose of even more waste in the cement
manufacturing process. Successive new ideas havebeen implemented, including eco-cement, chlorine
bypass systems and the AK system (all discussed indetail in Chapter 9).
The above has provided an outline of developments inJapanese cement manufacturing technology over the past
half-century since the 1960s. Items (1) to (5) above are
discussed in this chapter. Chapter 6 provides a moredetailed discussion of (6) and (7); (8) is discussed in
Chapters 7 and 8, while Chapter 9 discusses (9) and (10).

Maximum
Capacityt/D

Output per
Capacity3
kg/m -h

1,520

38.8

3,300

Lepol (L)

850

63.0

2,800

Shaft (S)

890

125.4

260

New calcined lime burning process (NCB)

450

167.6

2,600

Suspension preheater (SP)

760

64.4

5,300

New suspension preheater (NSP)

710

141.0

8,000

Attached filter and boiler (WFB)

1,520

35.4

740

Attached filter (WF)

1,390

23.7

860

Long (W)

1,240

22.9

2,200

Lepol (WFL)

920

48.7

850

Note 1) The “heat consumption” column shows
kilocalories of heat per kilogram of clinker (kgcl’= kg-clinker).
“Output per capacity” represents the clinker
output per hour per cubic meter of kiln capacity.
Note 2) “Heat consumption” only refers to “burning heat
blown into the rotary kiln”.
To compare NCB (new calcined lime burning
process) with other methods, the limekiln heat(around 550 kcal/kgcl’) must be added.
The SP kiln was developed by German plant
manufacturer Humboldt in 1950 to (1) achieve heatexchange by suspending powdered raw materials in kiln
exhaust gas and to (2) preheat and decarbonize raw
materials using residual heat in exhaust gas, thereby (3)gaining greater thermal efficiency than other conventional
kiln types. Later, Polysius, Wedag, Krupp (all Germany),
FL Smith (Denmark) and other companies announced
their own SP kilns, each with different designs but thesame basic principle. Figure 5.2 shows a structural
diagram of a typical SP kiln and the later improved NSP
kiln (details in 5.2).
The SP system was superior to conventional kiln
systems in three main aspects: better thermal efficiency,
capability for upscaling and capability for long-term
continuous operation. These features are discussed below.
5.1.1
SP Kiln Features 1) 2) 3) 5) 6)(1) Good Thermal Efficiency
The key to good thermal efficiency (see “HeatConsumption” column in Table 5.1) is the “suspension
preheater”, an innovative mechanism for exchanging heat
between the hot gas and the raw material.

History of Cement Manufacturing Technology

46

[NSP System](New Suspension Preheater)[SP System](Suspension Preheater)

Raw material
powder

Raw material
powderExhaust gas fan

Exhaust gas fanPreheater

High-temperature gas flow

Coal

Hot air current

BurnerCoal
Exhaustgas fan[see right figure]

CalcinerPreheater

Flow of raw material powder
into clinker

Blowerfan

Rotary kiln

Cooling fan

Rotary kiln

Clinker
CoolerFig. 5.2 Comparative Structures of SP and NSP Systems 1)

47

Table 5.2 SP Kiln Heat Balance (unit: kcal/kg-clinker) 6)
Type(no. of kilns)

Heat input

Item
Heat from fuel combustion
Other
Total heat input
Heat used for burning clinker
Sensible heat from preheater
exhaust gas (including sprayedwater evaporation heat)
Heat output

The raw material is dried, proportioned, ground andblended (homogenized). It is then transported to thepreheater through the constant feed weigher (CFW) andfed into the hot gas from the top (see Figure 5.2). The
powder goes downwards while repeating a cycle of
VXVSHQVLRQĺKHDWLQJĺVROLGVHSDUDWLQJDWHDFKF\FORQH
(four to five stages). It is decarbonized to around 40% andthen enters the rotary kiln.
Meanwhile, the kiln exhaust gas (1050-1100ºC) rises,
exchanging heat with the raw material at each cyclone.
By the time the gas exits the highest cyclone, it has
dropped in temperature to 350-370ºC. This residual heatis drawn out of the preheater by the exhaust gas fan andthen utilized for waste heat power generation and fordrying raw materials. Most of SP kilns have four-stage
cyclones; however, SP kilns with five stages have been
built to improve heat exchange even further.
The overall preheater system is an ingenious
mechanism designed for the principles of heat exchange.
The raw material is fed in from the highest point at the
top and then undergoes thermally efficient co-current heatexchange at each cyclone stage. It goes down througheach level by gravity and undergoes counter-current heatexchange as it reaches the higher temperature zone.
Around 40% of the CO2 in the CaCO3 is decarbonized,
while heat consumption improves to 3,150-3,250
kJ/kg-clinker. The system is also compatible with larger
kiln sizes and capable of long-term stable operation, as
discussed below.
Table 5.2 shows the heat balance of a SP kiln.
Although it appears from the table that there is little
difference in relative merit between the types, the data
have not been compared under identical conditions. It
would thus be fair to conclude that “no substantial
difference between models has been confirmed”. Table
4.2 provides a definition of burning efficiency.

Heat escaping in the clinker
Sensible heat from cooler
exhaust gas
Radiant and other heat loss
Other
Total heat output

Burning efficiency (%)

SP Kilns( 97.1)816.7( 2.9)
24.3(100.0)841.0( 50.6)
425.9

Humboldt(14)( 97.6)828.9( 2.4)
20.6(100.0)849.5( 47.3)401.1( 20.2)169.5( 2.9)
24.0( 14.2)119.4( 11.0)92.2( 1.1)
10.0(100.0)841.0
50.8

Dopol (21)

Wedag (7)Smith (1)Total (43)

( 97.1)785.8( 2.9)
23.4(100.0)809.2( 52.3)423.1( 97.1)782.0( 2.9)
23.1(100.0)805.1( 53.7)432.9( 97.3)814.8( 2.7)
23.0(100.0)837.8( 49.8)417.5( 22.2)188.6( 20.9)169.1( 21.9)176.1( 21.0)175.8( 1.9)
16.4( 13.2)112.3( 13.4)114.0( 2.0)
17.1(100.0)849.5
46.8( 2.9)
23.2( 12.6)102.2( 9.3)
75.1( 2.0)
16.5(100.0)809.2
51.9( 4.1)
33.3( 0)
0( 19.2)154.3( 1.1)
8.5(100.0)805.1
52.9( 2.6)
21.6( 13.3)111.5( 11.7)98.0( 1.6)
13.3(100.0)837.8
49.7(2) Capability for Long-run Operation and Upscaling
As the Japanese economy boomed, there was a rapid
increase in demand for cement. This placed high demandon cement plants to expand in size and production
capacity. With these economic conditions, most kilns
built from the mid-1960s onwards were SP kilns. SP kilns
offered increased daily production capacity as well as
long-run operation; that is, increasing both (daily
production capacity) × (number of days of continuous
operation).
The two advantages of SP kilns, upscaling andlong-run operation, were due to the preheater, which had
no moving parts, boiler pipes or other wearing parts in thehigh-temperature gas channel. Some additional
explanation is given below (see Table 5.1).
Lepol kilns are not markedly inferior to SP kilns interms of heat consumption. They are also easier to use,considering that they are not affected by cyclone blockage,a drawback with SP kilns discussed later. However, as
discussed in 4.2.4, the Lepol preheater has a grate that iscontinuously moving in the high-temperature gas flow at

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March900-1,000ºC. At larger sizes, this is susceptible tomechanical breakdown and failure, meaning a maximum
output of around 2,000t/d. As a result, when large-scale
SP and NSP kilns were built in the 1980s and later,
capable of producing over 3,000t/d, the Lepol kiln
disappeared from the Japanese cement industry.
Kilns with attached boilers (dry process and wet
process) were no match for the SP kiln in terms of heatconsumption. They also required several scheduled
breaks per year for boiler pipe maintenance and boiler
inspections and could not operate for more than half ayear at a time. The structure of the waste heat boiler alsomeant that kilns with attached boilers reached theirmaximum size in the 1960s.
While wet process long kilns were no match for SP
kilns in terms of heat consumption, they were adequate interms of long-run operation. However, the scale of thekilns (diameter and length) was the maximum possible interms of the mechanical structure and it would have beendifficult to make them any larger than the existing kilns at
the time. Since long kilns were already large in size, insome cases a SP tower was added to increase production
two or more times over. These were called “converted”
long kilns.
5.1.2
Issues with SP Kilns
The above advantages enabled SP kilns to dominate
existing kiln types within a short time. However, several
issues came to the fore. These included cyclone blockage
and firebrick lifespan issues, as discussed below.
(1) Cyclone Blockage
The greatest problem with SP kilns is cyclone blockage.
With high-temperature raw material flowing through thecyclone, any low-melting compounds (mainly sodium or
potassium salts) contained in the raw material or theexhaust gas melt and adhere to the inner wall of thecyclone. As this builds up and peels off, it can cause ablockage in the raw material outlet chute at the lower endof the cyclone. Once the cyclone outlet is blocked, thecyclone immediately fills up with high-temperature raw
material due to the several tons of raw materials flowing
through it every minute. The kiln is forced to stop while
the dust is manually removed from the cyclone. This is ahazardous task in a high-temperature environment.
Stopping the kiln also causes significant financial loss.
Countermeasures taken include the following:(1) Selecting raw materials with low alkali content(2) Efforts at stable preheater operation (keeping
exhaust gas temperature stable and minimizing
variations in raw material amount andcomposition)(3) Periodic (e.g., once per shift) coating removalfrom the interior of the cyclone (automatic air
blowers and manually using high-pressure water)
The reality at most plants is that efforts are made toprevent cyclone blockage using combinations of themethods (1), (2) and (3) above, but blockage still occurs.
This issue of cyclone blockage remained largely the samefor the NSP kilns that followed.
A major improvement came in 1990 with the inventionof the chlorine bypass by Chichibu Cement (nowTaiheiyo Cement). A chlorine bypass is a device thatdraws some of the hot gas out of the system when theconcentration of low-melting alkalis in the preheater getstoo high. More details are given in 9.2.2. This systemsignificantly reduced the cyclone blockage issue.
Originally invented as a means of preventing cyclone
blockage, chlorine bypass systems are now an
indispensable part of waste treatment at cement plants.
(2) Lifespan of Firebrick Lining
SP kilns were chosen for new facilities built in the
1960s and 1970s for reasons of thermal efficiency,
long-term continuous operation and upscaling. However,even these kilns faced an obstacle when upscaling todiameters of 6m and burning outputs of 5,000t/d. This
was the issue of the firebrick lining lifespan.
Japan’s first SP kiln started operating in 1963. It was
4m in diameter, 62m long and had an output of 1,200t/d.
Thereafter, new kilns and converted kilns were scaled
successively larger. The largest kiln was built in 1972
with a diameter of 6.2m, 125m in length and with an
output of 5,300t/d. The largest kiln was built in 1972 witha diameter of 6.2m, 125m in length and with an output of
5,300t/d.
It became apparent that there were limitations on thelong-term operation of the kilns. As the kiln approached
6m in diameter, the lifespan of the firebricks lining theinterior of the kiln grew shorter. The two main factors
affecting the lifespan of the firebricks are given below.
(1) The larger the diameter of the kiln, the weaker thearch support for the firebricks lining. This
increased the risk of bricks falling during
operation.
(2) The greater the kiln output, the more fuel required
to be blown into the kiln. The greater the heat loadon the burning area (the hottest section), the lower
the life expectancy of the refractory.
Surmounting this obstacle was the main objective forthe development of the NSP kiln, discussed in thefollowing section.
History of Cement Manufacturing Technology

48

5.2 NSP Kilns: World-Leading
Japanese
1) 2) 3) 5) 6)
Technology

The NSP kiln is a Japanese technology still usedthroughout the world today. It was developed by several
Japanese cement companies, either independently or incollaboration with plant manufacturers. Several different
successful systems were developed, but all of themincluded a separate furnace (calciner) with the preheater,
thereby improving the decarbonization rate of the raw
material and increasing the output of the rotary kiln.
Figure 1.4 shows an exterior photograph of an NSP
preheater and kiln. Figure 5.2 shows a comparison of the
SP and NSP kiln structures. Figure 5.3 shows acomparison of the burning processes.
CaCO3 ĺ&D2&22 – 467 kcal/kg-clinker

Raw powder

Pre-heating

Calcination

Clinker compound formation

Cementclinker

Burning

40% (calcination rate)
Suspension preheater
Rotary kiln
Suspension
preheater

Calciner

85% (calcination
rate)

Rotary kiln

Fig. 5.3 Comparison of SP and NSP Burning Reaction
Processes 6)

As shown in Figure 5.3, SP kiln preheaters have a raw
material decarbonization rate of 40%. The remaining 60%
calcination and the burning reaction have to be carried out
in the rotary kiln with poor thermal efficiency. By
contrast, the NSP system has a calciner added to thepreheater. The heat needed for decarbonization is
supplied separately by the calciner, thereby increasing thedecarbonization rate to 85% or higher. Only the little
remaining calcination and the exothermic burning
reaction are carried out in the rotary kiln. This has made it
possible to more than double the output of the same sizedrotary kiln (see Table 5.1). Table 5.3 shows an example
NSP kiln heat balance.
5.2.1

The cement industry is an energy-intensive industry.
Developing energy-conserving technologies is anunchanging goal for the experts in the industry. As soon
as the SP kiln was introduced in Japan, Japanese cement
manufacturers began to conceive the basic idea of the
NSP kiln: adding an auxiliary furnace to the preheater inorder to increase the efficiency of limestone
decarboxylation, the most heat-consuming part of thecement burning process, thereby increasing the kiln’sburning output per capacity as well as its thermal
efficiency. In a sense, this was a natural progression. If
the idea could be realized, it would definitely increase SP
kiln production and save more energy. The “new calcined
lime burning process”, still used by Onoda Cement at thetime, gave credibility to the idea.
It was well known in the cement industry at the timethat the burning output per kiln capacity using theimproved burning method was so much higher than any
other method, including the SP kiln, that it was in aleague of its own (see Table 5.1). Japanese cement
manufacturers were leading the West with advanced
cement manufacturing technology. These experts tookhold of the NSP idea because they had the uniquely
Japanese new calcined lime burning process right before
their eyes.
From around 1965, Mitsubishi Cement teamed up with
Mitsubishi Heavy Industries to work on developing NSP
kilns. Chichibu Cement did the same with
Ishikawajima-Harima Heavy Industries, while Onoda
Cement took the proprietary development route (working
in collaboration with Kawasaki Heavy Industries at theactual kiln construction stage). The development aims
were: (1) to make the SP kiln more thermally efficient;(2) to achieve long-term continuous operation for the SP
kiln; (3) to increase SP kiln capacity.
Japan’s first (= the world’s first) working NSP kiln wascompleted in December 1971 at the Mitsubishi Cement
Higashitani Plant in Fukuoka. Mitsubishi Cement and
Mitsubishi Heavy Industries named this NSP kiln the“MFC type”.

The NSP Kiln Concept
Table 5.3 NSP Kiln Heat Balance (example SF kiln; clinker output: 8,000t/d) 6)

Item
Heat from fuelcombustion
Sensible heat of fuelHeat Input
Heat(kcal/kg clinker)
745.0

Sensible heat of raw
materials
Sensible heat of primary
air

Total

49

3.1

Heat Output
Rate
(%)

Item

97.0 Heat used for burning clinker

Heat(kcal/kg clinker)
420.9

Rate
(%)
54.8

4.7

0.6

12.2

0.4 Heat used for evaporating moisture content
of raw materials
1.6 Heat escaping in the preheater exhaust gas

166.5

21.6

7.5

1.0 Heat escaping in the cooler exhaust gas

85.0

11.1

17.9
7.2
66.6
767.8

2.3
0.9
8.7
100.0

767.8

Heat escaping in the clinker
Heat escaping in the dust
Radiant and other heat loss
100.0
Total

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchIn July 1972, Chichibu Cement and Ishikawajima-Harima
Heavy Industries started operating the “SF type” at the
Chichibu No. 1 Plant in Saitama. In December the same
year, Onoda Cement began operation of its
independently-developed “RSP type” kiln at its Tahara
Plant in Aichi. Within one short year from the end of1971, three NSP systems had commenced operation.
Although other major cement companies, including
Nihon Cement and Sumitomo Cement, initially adopted
NSP kilns developed by other companies, Sumitomo
Cement eventually developed its own “SCS type” NSP
kiln and started operating it in 1979 through its subsidiarycompany Hachinohe Cement (Aomori Prefecture). Nihon
Cement teamed up with Kobe Steel to develop the “DDtype” NSP kiln and started operating it at its Kamiiso
Plant in Hokkaido in 1979.
(Note) MFC: Mitsubishi Fluidized Calciner System
SF: Suspension Preheater & Flash Furnace
RSP: Reinforced Suspension Preheater
DD: Dual Combustion and Denitration Process
SCS: Sumitomo Cross Suspension and Spouted
Calciner
Later new models and improvements to NSP kilns
were released. Table 5.4 shows the different NSP kilns
developed prior to 1982.
Table 5.4 NSP Types (as at 1982) 2)
Type

No. ofkilns(Note)
Average
capacity (t/d)

Developed by
Nihon Cement
Kobe Steel

DD

7

3,950

FLS

1

4,001

F.L. Smith

GG

2

3,300

Mitsubishi Heavy
Industries

KSV.
NKSV

8

3,600

Kawasaki Heavy
Industries

MFC
NMFC

16

3,532

Mitsubishi Kogyo Cement

RSP

12

3,258

Onoda Cement

SCS

4

3,780

Sumitomo Cement

SF.
NSF.
CSF

19

3,776

Chichibu Cement
Ishikawajima-Harima
Heavy Industries

Total

69

3,617

(Note) Average capacity calculated based on Cement
Association notified capacity.
5.2.2
NSP Kiln Features
Although the developers of the different models of
NSP kiln each advocated their own distinguishingfeatures, it would be difficult to compare them without
identical raw materials, preceding and following
processes and other conditions. Technically speaking,there is very little difference between the models.
Accordingly, a detailed comparison between the different
models of NSP kiln has been omitted from this report.
Ultimately, the NSP kilns that were developed clearly
had the following outstanding characteristics 4).
1) The kilns were capable of greater output per capacity

and were able to be scaled up in volume. The capital
investment and installation area required were alsoless than for SP kilns of the same size. The largest
working kiln had a daily output of 9,000 tons, with an
output per capacity of 130-150kg/m3h, compared to
the 60-70kg/m3h achieved by the SP kiln.
2) Kiln operation was stable. Since the raw material was
calcined before being fed into the kiln, the kiln could
operate in a stable state. Consequently, it was easy toadopt computerized process control.
3) Since the heat load inside the kiln was reduced, thefirebrick lining had a longer service life, making
longer continuous operation possible.
Improved refractory SP kilns 800-900g/t-clinker
consumption rate:
NSP kilns 500-600g/t-clinker(Note) Refractory consumption rate: the figure
obtained by dividing the weight of the lining
refractory by the volume of clinker produced
through the kiln by the time the lined
refractory was removed.
4) Since the temperature inside the calciner does nothave to be as high as inside the kiln, lower quality
fuel such as low-grade coal could be used.
5) NOx emissions were low, while SOx absorption was
as high as the SP kiln.
As per the above, the NSP kiln not only dramaticallyincreased the production capacity per kiln, but also had asignificant impact in aspects of energy conservation, laborsaving, automatization and computerized control. It wasalso epoch-making in terms of environmental measures
for its effective low-NOx (nitrogen oxide) burning. The
kiln drew much attention, both in Japan and overseas. The
efficacy of the NSP kiln as a low-NOx countermeasure isdiscussed in 6.1.1.
The successful technological development of the NSP
kiln prompted Japanese cement companies to build up
their technological development know-how. Companies
successively began to develop new
cement-manufacturing-related machinery. Japan came tolead the world in cement manufacturing technology.
Currently, all cement manufacturing in Japan is done by
SP and NSP kilns. NSP technology has also been actively
licensed overseas. In 1974, Ishikawajima-Harima Heavy
Industries and Chichibu Cement licensed SF kiln
technology to Fuller (USA). This was Japan’s first
cement technology export. After that, Onoda Cement
licensed RSP technology to Creusot-Loire (France),
Allis-Chalmers (USA) and other overseas companies.

History of Cement Manufacturing Technology

50

5.3 Structural Reform of the Cement Industry
achieved through SP/NSP Kilns and Bulk2) 3)
Transportation
From the 1970s to the 1980s, the cement industry
experienced trending growth in demand, but also somesevere conditions, as given below.
(1) Tight labor market due to the booming economy,
with wages rising substantially every year(2) Substantially rising energy prices due to the oilcrises and oil cartels(3) Pressure to invest in pollution control facilities in
response to tightening pollution regulations
In order to overcome the severe business conditions
caused by these external factors, cement companies
embarked on drastic “structural reforms”. This meantconsolidating plants and selecting “priority plants”. Up tothat point, fixed manufacturing costs such as capital
investment and repair costs were distributed across allplants using the same evaluation criteria, despite thedifferences between “major plants” and “minor plants”.
This changed to a policy of “concentrating management
resources on priority plants”. The following selection
criteria were used for determining “priority plants”.
(1) Sufficient limestone deposits for future supply(2) Convincing perspective for future expansion of
production and market to keep up with both
SP/NSP investment and pollution control
investment(3) Accessible for bulk shipping by tanker orcompetitive access to a big market by landtransportation
This plant consolidation made it possible to increase
the labor productivity of each company as well as
efficiently and effectively implement investment notdirectly related to manufacturing, such as pollution
control investment. Plants that were not designated aspriority plants were either shut down or split off into
separate entities making their own profits, such as byengaging in operations outside of the cement industry.
This production structure rationalization of the 1970s
and 1980s was a matter of companies selecting andconsolidating their own plants; in other words, internalrationalization. Cement production reached an
unprecedented high in 1995, after which the demand for
cement began to decline. This meant it would be difficult
for cement companies to survive by internalrationalization measures alone. To avert this crisis, theindustry underwent some mergers and other forms ofreorganization. Onoda Cement merged with Chichibu
Cement in 1994 to form Chichibu Onoda, while
Sumitomo Cement merged with Osaka Cement to form
Sumitomo Osaka Cement. In 1998, Chichibu Onoda
merged with Nihon Cement to form Taiheiyo Cement.
Ube Industries partnered with Mitsubishi Materials
Corporation to establish the joint venture Ube-Mitsubishi
Cement Corporation. Following these changes, the51merged companies then carried out further plantconsolidation that went beyond the limits of the former
companies.
Labor productivity (t)Number of employees (individuals)

Number of plant workers
Labor productivity(calendar year)

Fig. 5.4 Trends in Cement Plant Labor Productivity 1)
Table 5.5 Changes in Cement Plant Numbers and Kiln
Numbers 7)
Year

No. ofplantsNo. of
kilns

1970
1975
1980
1985
1990
1995
1999
2000

58
58
53
44
41
41
39
37

226
246
192
98
80
81
75
65

Cement output Clinker output(mt-cl/y)(mt-cl)
86.4
120.8
126.4
98.0
87.2
97.6
95.6
87.2

54.9
63.2
86.3
70.7
75.3
89.1
74.3
75.6

No. ofemployees

Labor
productivity(t/y, man)

16,54914,774
10,830
8,617
6,949
5,830
4,758
4,387

3,316
4,275
7,965
8,207
10,834
15,282
15,606
17,227

As shown in Table 5.5, in the three decades from 1970
WRWKHQXPEHURISODQWVGURSSHGWRDURXQGҀWKH
QXPEHURINLOQVGURSSHGWRDURXQGѿDQGWKHQXPEHURI
employees dropped to around ¼. During this time, clinker
output increased by around 1.4 times, while laborproductivity improved by around 5.2 times (Figure 5.4).
Thus, through plant consolidation, cement companies
were able to overcome the severe conditions imposed by
the shift from high growth to low growth and reduced
demand. It should be noted that these administrative
efforts were undergirded by technology infrastructure,including plant upscaling through SP and NSP systems
and bulk cement distribution systems for transporting
cement (see 4.12.3).

5.4 Upscaling and Energy-Saving of the Raw
Materials Process
As the SP and NSP systems made the burning processcapable of upscaling and more energy efficient, it was
only natural that the preceding and following processes ofraw materials and finishing had to be capable of upscaling
and more energy efficient as well. This report discusses
the upscaling of plant raw material receiving facilities andupscaling and energy-saving in the drying and grinding
processes.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March5.4.1

Upscaling of Raw Material Receiving
Facilities: Stacker & Reclaimer Systems 8)
The upscaling of kilns through the SP and NSP
systems inevitably meant that raw materials yards had toincrease in scale (storage volume and handling capacity).
The measures used to achieve this varied according to theconditions at each plant site. Naturally, a plant near themountains could have a smaller ore storage area, but thefurther the plant from the mine, the greater the ore storage
area had to be.
Plants with several large kilns capable of a daily output
of 5,000 tons or more need facilities that can handle
receiving 10,000 tons of limestone per day and deliveringto the production line more than 500 tons per hour. One
means of solving this is for cement plants to adopt a
stacker & reclaimer system, used by ore mines, coalmines, ironworks, power stations and other facilities forhandling large volumes of granular material, such as ironore or coal.

Fig. 5.5 Stacker & Reclaimer

9)This system is also called bed-blending. The mined
raw material is firstly stacked in alternating layers by thestacker (the arm-shaped device at the left of Figure 5.5). It
is then taken up by the reclaimer (the triangle-shaped
device at the right of the figure) working perpendicular tothe layers. This has the advantage in that it is possible forthe raw materials taken up from the stack to have evenless variation than the raw material received. In that sense,
this system has a positive effect on raw material
homogeneity. Another major advantage is that it canoperate unattended. In terms of capacity, the conventional
crane grab bucket system could shift around 300t/h,
whereas the stacker & reclaimer system could shift over
1,000t/h and was more economically advantageous thegreater the amount.
With regard to receiving and discharging clay materials,
issues were mostly dealt with by expanding andreinforcing pre-SP/NSP systems (e.g. crane grab-bucket
system) because of (1) smaller quantities than limestoneand (2) stickiness of materials.

5.4.2

Upscaling and Energy-Saving of Raw
Material Drying and Grinding Processes
Until the 1960s, raw materials were dried and groundusing a system of separate drying and grinding, in which
the limestone and clay received were:(1) dried in a limestone drier or clay drier (both rotary
driers), then(2) weighed proportionately with a constant feed
weigher (CFW), and then(3) fed into a tube mill to be ground together.
The hot air furnaces were set up for limestone and clay
separately. When the SP kiln system was introduced, withexhaust gas coming out of the highest cyclone of thesuspension preheater at around 350ºC, the method was
generally adopted of utilizing the residual heat in theexhaust gas to dry the raw materials.
Initially, exhaust gas waste heat drying of raw
materials was carried out separately from grinding.
Eventually, a system was introduced in which exhaust gas
was directed into the raw mill, allowing drying andgrinding to be carried out simultaneously. The
simultaneous drying and grinding system saved on repairs
and maintenance and was also more economical onenergy than the separate dryer system. Accordingly,
separate dryer systems were rarely used for raw materials
processes at new facilities from the 1970s on.
Simultaneous drying and grinding mills took the formof tube mills or vertical roller mills. The tube mill used as
an example in this report is the double rotator mill; thevertical roller mill used as an example is the Loeschemill.
(1) Double Rotator Mill 6) 10) 11)
The double rotator mill is a simultaneous grinding anddrying ball mill developed by Polysius (Germany). It was
first used in a Japanese cement plant in 1963 at the
Mitsubishi Cement Higashitani plant in Fukuoka. There
were reported to be 28 of these mills in operation in
August 1975.
This type of mill is characterized by having a drying
compartment on the raw material feed side and a groundmaterial outlet in the center of the mill; it is acombination of an air-swept system (see Note 1) and aclosed-circuit system with a separator. The mill itself
comprises a drying compartment, 1st and 2nd grinding
compartments and a central discharge chamber. When
preheater exhaust gas at 330-350ºC is used, this type ofmill is capable of drying only around 5% of the moisture
content in the feedstock. As discussed later, vertical mills
were the raw material mill of choice for new facilities
from the late 1970s. See cited reference (10) for moredetails on double rotator mills.

History of Cement Manufacturing Technology52

(2) Vertical Mill (Roller Mill) 11) 12)
The vertical mill is a type of mill in which the raw
material is fed onto a rotating table and then pressed andground by multiple rollers. A separator is positioned
above the rollers, so that drying, grinding and classifying
are integrated into a single machine. This provides thefollowing advantages.
(1) Smaller installation area and less noise(2) More efficient grinding and less power consumed
than tube mills(3) Since the ground material spends less time within
the mill, any variations in raw material
proportioning can be dealt with quickly, which
also allows more consistent quality(4) Drying and grinding can be carried out
simultaneously by directing high-temperature
exhaust gas through the mill
Due to reason (4) above, this type of mill was widelyadopted for raw material grinding and coal grinding. It
was very effective in simplifying processes andconserving energy. Section 5.5.5 discusses the adoptionof vertical mills into the finish grinding process.
Vertical roller mills include Loesche mills and MPS
mills. In Japan, the Ube Loesche mill, manufactured by
Ube Industries under license from Loesche (Germany),came to dominate the market. Figure 5.6 shows (1) theexterior view and (2) the internal structure of a large-scale
LM32/4 Ube Loesche mill, as well as (3) the vertical mill
grinding mechanism.
Operation of the mill is as follows.
Four rollers on a rotating table press against the tableby means of hydraulic cylinder. The raw material is fed infrom the chute and drops down near the center of thetable. It is pushed outwards by centrifugal force andground as it goes between the table and the rollers. The
mill is a simultaneous grinding and drying mill; exhaustgas is fed into the mill by fan through a lower duct. At
this point, the exhaust gas is subjected to rotating force

from a blade ring on the circumference of the table. The
resulting hot wind blows over the ground material
overflowing from the edge of the table. The groundmaterial is blown into a separator at the top of the mill.
The coarse particles are sent outwards and drop back onto
the table to be ground again. The fine powder passes
between the blades of the separator with the gas and iscollected by a cyclone collector.
The figures below indicate an example of improved
power consumption between a tube mill and a verticalmill for grinding raw materials. 7)(calculation prerequisites)
Grinding capacity: 200t/h
Annual operating time: 7,000hrs(power consumption comparison)
Tube mill: 20-26kwh/t-raw material
Vertical mill: 14-18 kwh/t-raw material
This represents an improvement in power consumptionof around 30%. Japan’s first Loesche mill was installed at
the Ube Industries Isa plant in 1959. This early type wassmall in capacity and the rollers and table were madefrom poor materials, meaning that a lot of time was spent
on maintenance. Therefore, the spread of the Loesche mill
was not so fast. Improvements in both mechanicalstructure and structural materials allowed gradualupscaling of the system. In the 1970s, a large-scale
Loesche mill was developed that had a grinding capacityof over 200t/h. The vertical mill grew rapidly inpopularity and by the mid-1970s had become the first
choice of raw materials mill for new installations.
As Loesche mills grew in size, it became possible touse one raw materials mill (Loesche mill) per kiln, whichsignificantly simplified the process layout. The “one kiln,
one mill” system was first achieved by Ube Industries at
the Kanda plant in Fukuoka in 1977.

5.5 Energy-Saving in the Finishing (Cement
Grinding) Process

Raw material

Product(10) Three-stagegate(7) Separator(2) Upper casing(6) Grinding roller

Roller(5) Swing lever(9) Blade ring(3) Grinding table(1) Lower casing

Pushing force(8) HydrauliccylinderRaw material(4) Vertical
reducer

Direction of table rotation(1) Loesche Mill Exterior
View 9)(2) Loesche Mill Internal
Structure 13)(3) Loesche Mill Grinding
Mechanism 13)

Fig. 5.6 Vertical Grinding Mill (Loesche Mill)

53

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchWith the advent of SP and NSP kilns, the main
contribution to upscaling and energy-saving in the raw
materials process was the vertical roller mill, as discussed
above. Meanwhile, the first stage of upscaling andenergy-saving in the finishing process (1960s and 1970s)
was achieved by upscaling of tube mills, adding grinding
aids and the use of classifying liners and smaller balls.
The second stage (1980s onwards) saw progress throughthe use of highly efficient separators (such as the
O-SEPA) and pre-crushers. Figure 4.13 shows thetransitions in the upscaling of finishing tube mills.
The use of vertical roller mills for finishing (cement
grinding) was hindered by issues with operation,
maintenance and cement quality. In 1988, the Japanesedeveloped the OK Mill, a vertical cement grinding mill.
This was a great achievement; the design idea andtechnology spread throughout the world and various kindsof vertical mills began to be used for cement grinding.
Below is a detailed discussion of the first and second
stages of energy-economizing the tube mill in thefinishing process. The vertical roller mill for cement
grinding is discussed in 5.5.5.
5.5.1

Difference in Powder FinenessManagement Indicators between the Raw
Materials Process and the Finishing
Process
The raw materials process and the finishing process
both center around grinding and classifying. In bothprocesses, powder fineness is an important quality control
point for the product being sent to the next stage.
However, powder fineness can be represented in several
ways, such as sieve residue, specific surface area andparticle size distribution. Due to the difference in function
between the raw materials process and the finishingprocess, the fineness is represented differently between
the two processes. Since understanding the energy
conservation initiatives for the two processes requires
understanding how fineness is represented for eachprocess, an explanation is given here.
(1) Fineness in controlling the raw materials
process: sieve residue
Fineness as a control for the raw materials process ismeasured by sieve residue, the amount of residue
remaining on the standard sieve. Currently, the main
PHDVXUHXVHGLVȝVLHYHUHVLGXHRQDȝ-,6VWDQGDUG
sieve.
The raw powder produced in the raw materials process
is sent on to the following burning process for the clinker
formation reaction. If this powder contains coarse
JUDQXOHV HJODUJHUWKDQȝ LWFRXOGFRPHRXWRIWKH
rotary kiln without having reacted properly. Quartz orother siliceous particles contained in siliceous raw

material is hard to grind and is prone to residual coarse
particles. If these coarse particles go through the kiln
without reacting, a corresponding amount of lime willremain in the clinker as “free lime” (see Note 4 ofChapter 3). This has an adverse effect on the quality of
the cement.
In terms of fineness control indicators in the raw
materials process, there are some advantages for
upscaling and energy saving because (1) it is a simple
process mostly measured by sieve residue and (2) the
ensuing burning process takes places within the plant.
(2) Fineness in controlling the finishing process:specific surface area and particle size
distribution
The end product of the finishing process is cement. The
cement is shipped out of the plant in its finished state. The
customer mixes it with water at the site of use, where it
undergoes a chemical reaction of setting and hardening to
finally form concrete. The setting and hardening reaction
process is the process of the cement powder being
dissolved in water and forming hydrates. Accordingly, theimportant control indicator for cement fineness is specificsurface area (cm2/g).
Another important element in controlling fineness inthe finishing process is particle size distribution. Particle
size distribution has a major effect on the setting processor the usability of the cement product. Cement with, tosome degree, a broad particle size distribution is deemed
as being easy to use, while cement with a narrow particle
size distribution requires more water to produce fresh
concrete of the same softness, resulting in a drop in
concrete strength. However, measuring particle size
distribution is not easy and it is difficult to carry out
measurements as a routine process control. Having said
that, if clinker burned under similar burning conditions
from similar raw materials is ground using similarly set
grinding and classifying machinery, there will be little
YDULDWLRQLQSDUWLFOHVL]HGLVWULEXWLRQ$FFRUGLQJO\ȝ
sieve residue testing is used as an alternative for routine
control.
Another important control point in the finishingprocess is grinding temperature. The grinding temperature
affects the dehydration of gypsum added during grinding.
The level of dehydration of the gypsum in the cement hasa significant impact on the setting of the cement, thereby
affecting the usability of the cement. The main factors
related to grinding temperature are (1) the temperature of
the clinker entering the mill and (2) the heat generated bygrinding.
In light of this, a setting test is included in the routine
control test items for cement. The results of this test
provide feedback for managing particle size distribution
ȝUHVLGXH DQGFHPHQWJULQGLQJWHPSHUDWXUH

History of Cement Manufacturing Technology

54

5.5.2
Grinding Aids 7) 14)
Grinding aids are a tertiary material added in trace
amounts during the grinding process to accelerate
grinding.
In tube mills, grinding efficiency usually decreases
significantly in the fine grinding stage. This is due toagglomeration of the fines, for two reasons: (1)agglomerated fines adhere to the mill lining and thegrinding media, forming a coating that reduces the impact
force of the mill; (2) agglomerated fines get mixed in withthe coarse particles by the separator and are recycled
through the mill. Grinding aids act to improve thegrinding efficiency by preventing this agglomeration.
An important condition for the use of grinding aids ispreventing deterioration in product quality. The increased
cost of adding grinding aids is outweighed by the
reduction in costs achieved by improving grinding
efficiency. Accordingly, due to cost versus effect,
grinding aids in the cement industry are used exclusively
in cement grinding and seldom in raw material grinding.
Research on the use of grinding aids in the finishingprocess began around 1930 in the United States, with theaim of utilizing lignin recovered from pulp waste liquid.
The effect was confirmed and in 1932 a product wasmarketed in the United States under the brand name RDA.
From around the mid-1950s, as the petrochemicalindustry developed, various developments were madeusing organic substances with additive effects. At thepresent time, most of grinding aids used in cement plants
are these petrochemical products.
In Japan, the JIS cement quality standard was amended
in 1973 to allow the use of aids, considerably later thanthe United States because of customers’ concerns over the
durability of concrete. After that, the use of grinding aids
prevailed. Diethylene glycol has been widely used inJapan, as well as triethanolamine, amine acetate and othercompounds.
These aids are usually used in finishing mills by
diluting them with five to ten parts water and spraying
them into the mill. The volume of additive is 0.01-0.03%
relative to the weight of the clinker. In terms of use effect,
the grinding volume is reported to increase by 4-6% for
every 0.01% of grinding aid added.
5.5.3
Classifying Liners and Small Balls 7) 11)
Raw materials mills and finishing mills both haveliners with lifters for (1) protecting the mill and (2)scraping the grinding media.
The second compartment in a finishing mill is for finegrinding. The use of smaller balls (17-20mm in diameter)
is known to improve efficiency by increasing the surface
area to enhance the grinding effect. However, withconventional liners with lifters, the small balls would
accumulate at the entry to the second compartment, while
the medium-sized balls would accumulate at the exit,

55

creating a reverse classifying effect and significantly
decreasing the grinding efficiency. It was therefore
difficult to make any dramatic decrease to the size of theballs.
Classifying liners (Figure 5.7) were developed toeliminate this reverse classifying effect. Classifying liners
slope towards the mill entry, causing the balls to travel
towards the entry point. The greater the ball diameter, thegreater the effect of the torque (centrifugal force) of themill and the closer the ball travels towards the entry. As aresult, the balls can be classified successively, with larger
balls closer to the entry to the second compartment. The
development of classifying liners made it possible to useballs with smaller diameters of 17-20mm. Fine grinding
could now be achieved without over-grinding.

Example 1

Example 2

Example 4

Example 3

Fig. 5.7 Classifying Liners in the Second Compartment ofa Finishing Mill 7)(Example 4 is a “lifting” type classifying liner)
The use of classifying liners and smaller balls isreported to have improved grinding power consumptionby 1-2kwh/t. Since the coarse grinding at the entry to thesecond compartment has also improved, the grinding
ability of the entire mill is sometimes improved byshortening the first compartment (lengthening the second
compartment).
5.5.4

O-SEPA: the Revolutionary JapaneseHighly Efficient “Eddy Current Separator”
The O-SEPA was developed from an original idea by
Takeshi Furukawa, an employee at the Onoda Cement
Central Research Institute. The first working machinecompleted in 1979 was the revolutionary Japanese highly
efficient separator.
Separators used in the cement industry grinding
process include the “first generation” of Gayco andSturtevant separators with internal fans, discussed in 4.6.3,
the “second generation” of cyclone air separators withexternal fans, and the “third generation” O-SEPA
separators, now used all over the world. “O-SEPA” wasthe brand name; therefore, when similar types ofseparators using the same principle began to be soldworldwide, common names also began to be used,
including “eddy current separator”, “rotor-type separator”
and “high efficiency separator (HES)”. In this report,“eddy current separator” is used.
The following provides a discussion of the principle,
structure, operational data and separating capability of the

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March(5) Secondary
air

Cyclone separator (before
remodeling)
O-SEPA (after
remodeling)

Fines
°C

Air
(5) Secondary
air

110.1

35.42

10.06

45.48

3230

1.2

25.9

2.2

135

112

126.7

30.78

5.25

36.03

3090

0.8

20.0

1.2

120

84

Cement temperature
Sprayed t/h3ȝP
residue %29ȝP
residue %(2) Dispersion
plate(3) Impact plate

Product fineness
Blaine cm /g(12) Rotating axis
(1) Feed material inlet

Power consumption
kWh/t
Total

Product

Mill output°C

Table 5.6 Comparison of Before and After Remodelingfrom Cyclone Separator to O-SEPA 15)

Mill(9) Product collecting duct(2) Operational Data 15)
Table 5.6 shows the operational data taken before andafter remodeling a large tube mill (4,000kw) from acyclone separator to an O-SEPA (N-3000).

Othermachinery(1) Principle and Structure of the O-SEPA 15) 16)
The O-SEPA is a type of air separator. The separating
principle is the same as that of the first- andsecond-generation separators. That is, “a machine that
separates fine powders and coarse particles by using thefact that the equilibrium relationship between the external
forces (gravity, centrifugal force, etc.) acting on solid
particles and the air resistance acting on as those particles
as they move through the air differs according to particle
size and density.”
The major advantage of the O-SEPA is that whereas
the first- and second-generation separators only separate
particles using a “free vortex” from guide vanes (blades
fixed on the outer circumference), the O-SEPA has asecondary separation in addition to the free vortex, using
a “forced vortex” from rotating eddy current adjusting
blades. Accordingly, O-SEPA type separators should betermed more accurately as “combined free vortex andforced vortex separators”.
Figure 5.8 shows the overall structure of an O-SEPA,
while Figure 5.9 shows a horizontal cross-section.

until it reaches the circumferential speed of rotation of theeddy current adjusting blades, goes between the eddy
current adjusting blades and is expelled into the productcollecting duct (9).
Meanwhile, the raw materials to be separated being fed
from the raw material inlet (1) travel past the rotating
dispersion plate (2) and impact plate (3) and are dispersed
into the separating space. The particles are first classified
by the swirl current caused by the guide vanes. They thenundergo a second classification determined by the balance
between the centrifugal force of the swirl current from theeddy current adjusting blades and the speed of the air
current flowing towards the center. The fine particles are
expelled to the product collecting duct. Incoming air fromthe tertiary air intake separates any remaining fineparticles adhering to the coarse particles collected in thecoarse particle collection cone (11).

Amount ground (t/h)

O-SEPA, the original eddy current separator, as well assome typical examples of its use in the cement grinding
process.

(4) Primary air(8) Rectifier(7) Eddy current
adjusting blades(10) Tertiary air(6) Guide vanes(10) Tertiary air(11) Coarse particle
collection cone

Coarse powder

Fig. 5.8

O-SEPA Structure 15)(7) Eddy current
adjusting bladesAir(4) Primary air(6) Guide vanes

Fig. 5.9
O-SEPA
Horizontal Cross-Section 15)

The air needed for separating can be dust-containing
air from a grinding mill, conveyors, outside air or any
mixture of these (one advantage of the O-SEPA). The air
comes in from the air intakes for primary air (4),secondary air (5) and tertiary air (10). As shown in Figure
5.9, the primary air and secondary air are drawn from theintakes in a tangential direction. These form an eddy
current by passing over the guide vanes (6) on a particularangle and are sent into the separating area. The separatingarea is a space between the guide vanes and the eddy
current adjusting blades (7), where the particles are
separating into coarse particles and fine particles by theseparating effect. The air current forms a tight horizontal
vortex through the action of the rotating eddy current
adjusting blades and the rectifier (8). This accelerates(3) Advantages of the O-SEPA 4) 15)
The O-SEPA has the following advantages.
a. Improved separating capability reduces the amount of
power used.
b. Specific surface area can be reduced with the same
cement quality level, reducing the amount of power
used.
c. Improved particle size distribution and lower cement
temperature improves cement quality.
d. Improved operational capability makes it easy to
switch the types of cement and maintain cement
quality.
e. Ability to handle large volumes of dust-containing air
from a mill and conveyors reduces dust emissions,which means improved working environment andgreater longevity of machinery.
f. Fewer machines means a simpler flow, fewer
machinery breakdowns and more stable operation. For
comparison, Figure 5.10 shows the flow diagrams for a
cyclone separator and an O-SEPA.
g. Far smaller installation space compared toconventional separators, making maintenance easy.

History of Cement Manufacturing Technology

56

Fan

Outsideair

Outsideair
Circulation
fan

Product

Bucket elevator

Fan

Separator

Gas

Dust
collector

PowderMill

Grinding material

PowderDust collector

Outside
air

Fan
Fan
Product

Grinding material

Outsideair

Bucket elevator(1) Cyclone Separator

Gas

The “OK mill” jointly developed by Onoda Cement
and Kobe Steel broke through these challenges.
Following pilot plant testing, the world’s first large-scalevertical cement grinding OK mill (130t/h) started
operation in July 1988 DWWKHLUƿIXQDWRSODQWMillFig. 5.10 Comparison of Cyclone Separator and O-SEPA
Separator Flow Diagrams 15)

In 1985, international giant Fuller (USA; now mergedwith FLSmidth) entered into a technology license
agreement with Onoda Cement for the O-SEPA
technology. The following year, CLE Technip (France)
also entered into a technology license agreement. The
worldwide spread of the O-SEPA began with these twoWestern companies and Onoda Engineering (nowTaiheiyo Engineering). The O-SEPA has also since been
applied in grinding processes for a range of othermaterials, including blast furnace slag, coal and limestone
powder (calcium carbonate), as well as raw materials forfine ceramics (e.g. silicon nitride and silicon carbide) andvarious kinds of powder fillers.
Following the development of the O-SEPA, companies
in Japan and overseas developed other “eddy current”
separators using the same principle.

(1) OK Mill Structure
The OK mill resolved the issues (1), (2) and (3) abovein the following ways 18) (see Figure 5.11).
(1) Vibration: The grinding rollers were shaped with anindentation in the center so as to limit the location of
the grinding. This reduced the area where the groundpowder was being pressed and ground, making it lesssusceptible to vibration. At the same time, it also
increased the grinding efficiency.
(2) Wear: Shaping the grinding rollers with anindentation in the center so as to limit the location of
the grinding also reduced the amount of wear.
Improving the metal material used in the rollers also
improved the abrasion resistance.
(3) Particle size distribution: Use of the OKS highly
efficient eddy current separator (a modified versionof the O-SEPA for vertical mills) made it possible tohave independent control over the separator rotation
speed, air flow, roller pressure, table dam height andother functions. As a result, it was easy to adjust therange of the particle size distribution to determine thequality of the end product.
Product
OKS separator

Hydraulic roller
pressure device

GrindingrollerGrinding
table
Nozzle5.5.5

Vertical Mills for Finish (Cement) Grinding:the Forerunner “OK Mill” 17) 18)
Vertical (roller) mills grind the raw materials
efficiently, thereby conserving energy. Because of this,various attempts were made by Japanese and Westernindustry pioneers to use vertical mills for cement grinding
as well. However, this was not easy to achieve, for thefollowing three main reasons (issues).
(1) Operation: The clinker is hard to grind and can cause
the mill to vibrate during grinding.
(2) Maintenance: For the same reason as above, theclinker causes wear and damage to the grindingrollers and table.
(3) Cement quality: Vertical mills produce a groundproduct (cement) with a narrow particle size
distribution, meaning more water is needed whenmixing the concrete, which reduces the strength ofthe cement.

57(1) OK Mill Exterior View 9)(2) OK Mill Structural Diagram

17)

Fig. 5.11 OK Mill

(2) Key to the Success of the OK Mill 18)
Many previous attempts to use a vertical mill in thefinishing process had failed. The reason the OK mill
succeeded was that it was a vertical mill with a modified
O-SEPA built in. The thought process for thedevelopment was as follows.
(1) In a vertical mill, the grinding efficiency has a linear
relationship to the pressure of the rollers on the table.
(2) The higher the pressure, the higher the grinding
efficiency but the narrower the particle size
distribution of the product.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

(3) The pressure has mechanical limitations as well as
the limitation of susceptibility to vibration.
(4) The table has a dam around the outer edge to adjust
the powder depth. The lower the height of the dam,
the better the grinding efficiency, but the less stable
the operation. Thus, “dam height” has a similarfunction to pressure in (1) and (2) above, as well asfunctioning to alter particle size distribution.
(5) Particle size distribution is usually considered inrelation to whether particles are fine or coarse andwhether distribution is wide or narrow.
(6) Both rotary separators (conventional separators usedin vertical mills) and eddy current separators regulatethese two factors of particle size distribution by
airflow and vane rotation speed.
(7) In both types of separators:* the greater the airflow, the coarser the product* the higher the vane rotation speed, the finer the
product* by adjusting the vane rotation speed, the samefineness can be achieved at different airflow levels* the greater the airflow, the narrower the particle
size distribution of the product(8) The two factors of particle size distribution can be
adjusted independently from each other in the eddy
current separator, unlike the rotary separator.
(9) Particle size distribution in cement grinding not only
affects the strength of the cement, but also its
workability. The narrower the particle size
distribution, the better for strength but the worse forworkability. In terms of workability, the cement iseasy to use if it has similar particle distribution asthat produced by a tube mill.
(10) From the above, in order to “increase grinding
efficiency without altering product particle size
distribution”, it was “necessary to have a separating
mechanism to compensate for the transition in
grinding mechanism from tube mill to vertical mill”.
Thus, it was necessary to have an eddy current
separator with freely adjustable particle size
distribution. The OK mill was the forerunner ofthese.
(3) OK Mill Operating Performance 17)
Tables 5.7 and 5.8 show data comparing theperformance of a new OK mill installed at the Taiheiyo&HPHQWƿIXQDWRSODQWZLWKDILQLVKLQJWXEHPLOOXVHGDW
the same plant to grind the same clinker. As shown in thetables, the quality of the OK mill cement, both ordinaryand high-early strength, is equal to or slightly higher thanconventional mill cement. Power consumption issignificantly improved.

Table 5.7 OK Mill Grinding Capability and Power
Consumption 17)
Type

Separator ProductMill
Amountrotation
Blainepower
ground t/h2
speed rpm cm /gkw

Mill
airflow3
m /minMill
OK mill

4750

71.7

Power used kwh/t
Mill

Other
machinery

Total

3210

135.5

3000

22.1

5.7

3280

99.2

3300

33.3

5.5

27.8
38.8

4390

103.3

2800

27.1

5.7

32.8

4350

21.0

950

45.2

7.5

52.7

Ordinary
Tube millHigh-earlystrength-

OK mill
Tube mill

4540

-

92.6
-

Table 5.8 OK Mill Ground Cement Quality Data 17)Type

Ordinary

High-earlystrength

Mill

Blaine2(cm /g)Compressive strength
Residue (%) Setting Setting time*2(kgf/cm )
Flow
water
(mm)
(%)
3ȝ 15ȝ
Initial Final
1-day 3-day 7-day 28-day

OK mill

3200

19.3

51.3

28.5

2-19

Tube
mill**

3280

20.3

53.2

28.4

2-24

3-29

253

-

142

243

420

OK mill

4350

5.0

34.4

30.8

1-32

2-27

247

181

311

399

485

Tube
mill**

4350

5.2

35.6

30.8

1-47

2-39

250

169

292

385

480

3-10

256

-

151

255

431

*hr-min. **tube mill

Prompted by the successful development of the OK
mill, other types of vertical finishing mill were also
developed, fitted with eddy current separators. Verticalcement grinding mills spread throughout the world.
5.5.6

Pre-crushers for Finishing Mills: Energy
Conservation Measures with Reduced
Demand for Cement 4) 7)
Pre-crushers for finishing mills are devices used at the
pre-tube-mill stage in the finishing process with the aimof improving the total power consumption of the process.
Pre-crushers can be the roller press type or the verticalmill type. The vertical mill type is a technology
developed in Japan.
The roller press type crushes clinker by feeding it
between a pair of biting rollers. Developed in Europe, it
gained considerable usage for a time due to its low cost.
However, it was often not as productive as expected due
to roller lifespan and poor maintainability.
The vertical mill type was a simplified version of ahighly efficient vertical roller mill without the separator.
The first was the CKP, was jointly developed in 1987 by
Chichibu Cement and Kawasaki Heavy Industries. After
that, the vertical mill type became the main pre-crusher
used. Figure 5.12 shows the structure and flow.
The following figures were reported as a result of
introducing the vertical mill type pre-crusher.

History of Cement Manufacturing Technology

58

(1) Finishing tube mill capacity: 30-60% increase(2) Finishing process power consumption: 10-20%
improvement
Material(gypsum)clinker

separator
damper or
sieve

RollerTable

productrollermill

tube mill

pre-crusher(1) Structure(2) Flow diagram

Fig. 5.12 Pre-crusher for a Finishing Mill (Vertical Mill Type)
7)

Following the development and commercialization of
the OK mill and other vertical mills for finish grinding,the Japanese cement industry went from maturity todecreased demand. Very few new finishing mills werebeing built. It was pointless to invest money in converting
to a vertical mill for power savings alone. In this cement
market environment, pre-crushers could be used toincrease the production of existing mills, while improving
specific power consumption (kwh/t). This was indeed atechnological development suited to the demands of thetime. Vertical mill pre-crusher technology was also
licensed overseas.

5.6 Waste Heat (Exhaust Heat) Power
Generation: Reclaiming and Utilizing Waste
7) 19)Heat to the Extreme
Two sources of exhaust gas heat energy from SP and
NSP kilns have been discussed previously: (1) preheater
exhaust gas (kiln exhaust gas) and (2) clinker cooler
exhaust gas. As also discussed, preheater exhaust gas isused for drying raw materials, while cooler exhaust gas isused for (1) secondary air in kiln burning, (2) calciner
combustion air, and (3) dry air for coal grinding. Until the
1970s, this was the extent of exhaust gas heat utilization.
With the popularization of the NSP system, the scale ofproduction per kiln increased. With this regard, a new
way of waste gas power generation was developed. The
heat from the 400ºC preheater exhaust gas and the 250ºC
cooler exhaust was recovered by the waste heat boiler andconverted to electricity by a mixed pressure steam turbine
and a power generator. This energy-recovering “waste
heat power generation facility” grew rapidly in popularity
from around 1980. The reason for this was that the power
output per ton of clinker averaged around 35-40kW,
meaning around 8,000kW per hour in a kiln with a
5,000t/d capacity, equating to investment profit.
NSP kiln systems fitted with waste heat power

59

generation facilities improved energy utilization
efficiency by more than 80% in the burning process. The
temperature of the preheater exhaust gas after passing
through the waste heat boiler was around 250ºC. This
dropped to around 100ºC after being used for drying raw
materials and the like after that. Cooler exhaust gas also
dropped to around 100ºC after passing through the waste
heat boiler. This left next to no further industrial
utilization value in either heat source. Any further
reduction in heat consumption in the burning process
would lead to a drop in waste power generation, meaning
it was ultimately not economically viable to invest in newenergy conservation measures. This was the result oftireless efforts in waste heat power generation by cement
technology developers, ever ambitious to wring bloodfrom a stone in energy conservation.

5.7 Computerized Control 4) 20)
This section discusses the development ofcomputerized technology to control processes in cement
manufacturing. Computerized control in the cement
manufacturing process comprises one large system
combining “specific cement manufacturing technology” +“temperature, pressure, chemical composition and othersensor technology” + “communication / information
processing devices (hardware)” + “system integration /control technology (software)”. All of those technologies
are still evolving rapidly, while the cement industry itself
is changing from “an industry that makes cement fromnatural materials” to “an industry that makes cement fromrecycled waste materials”. Accordingly, computerized
control in the cement manufacturing process is always inthe “present progressive form”.
Detailed explanations of technical terms related tocomputerized control can be found in specialized sources
and have been omitted from this report.
5.7.1

Introduction of Computerized Control to the
Cement Manufacturing Process 4) 20)
In 1958, American company Thompson Ramo
Woodridge (TWR) unveiled a control computer. In 1959,
Riverside Cement trialed a computer for proportioning
raw materials, while in 1964, Colton Plant of California
Portland Cement (CPC) trialed computers for controlling
the processes of raw materials proportioning and burning.
Thus, computers started spreading in use for processcontrol in the United States in the 1960s.
The Japanese cement industry also started introducing
computers for process control from the early 1960s. In
many cases, the first attempts were to develop
computerized control for the raw materials process.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchDevelopment for the burning process also began in the
1960s. Computers were used to gather and analyze
operational data to examine the characteristics of theburning process. It was difficult to model the cement
manufacturing process, particularly the burning process,as there was feedback between input and output, with a
lot of interference. It was thought that it would be
extremely difficult to implement computerized control forthese processes. Many bold attempts were made in
research and development to overcome this barrier. Byaround 1970, companies had some basic methods ofcomputerized control for the burning process more or lesscomplete. Reported examples of development include thefollowing methods 20).
(1) a static mathematical model inside the kiln(2) optimized kiln operation based on time-series
statistical analysis(3) detection of disturbances such as coating (anzatz)
falling and optimized operation for recovery
The 1970s saw the development of the NSP system anda transition in fuel from heavy oil to coal. This also had
an effect on controls. For example, switching to coalaround 1980 involved changing the existing analog
instrumentation to a digital one-loop controller.
By around 1990, the transition to NSP and coal burning
was mostly complete. Introduction of a distributed control
system (DCS) integrated everything into the control room.
Earnest efforts were being made to increase productivity
by saving labor.
From the 1990s, the variety and volume of wastematerials used in cement manufacturing processes started
to increase. These were added into the kiln system atvarious stages according to the composition andcharacteristics of the waste materials and the limitations
on plant layout. It became crucial to coordinate theprocessing speed with the DCS and the programmable
logic controller (PLC) in order to handle variations inmaterial type and control the stopping and starting of thefeeder, depending on how the recycled materials were to
be used.
Around 2000, the OPC standard (see Note 2) for
methods of communication between measurement control
devices such as DCS and applications started being used.
OPC communication functions meant that computer
systems could be built for process control without relying
on DCS manufacturers. Faster computing speeds also saw
process control computer control cycles drop fromminutes in the 1990s down to seconds.
By 2010, cathode ray tube (CRT) operation by DCS
and PLC was the norm for measurement control devices.
Most were using proportional integral derivative (PID)
control. Several controls in the raw materials
proportioning process and the burning process used

process control computers for higher order processes andthen via a gateway to “set point control” with adjusted
DCS loop parameters.
5.7.2

Difficulty of Computerized Control in
Cement Manufacturing 20)
Most of the fuel and raw materials used in the cement
industry are solids or powders of various different forms
and characteristics. They are prone to inconsistentbehavior, such as adhering together, blockages,
segregation (bias and separation of particles or constituent
ingredients) and flash (sudden bursts), which presents
major difficulties in measurement as well as control.
There is no way to measure the exact composition of raw
cement materials as they enter the kiln, even if what issent into the kiln is all natural materials and thecomposition variance and averages are known. The
burning process controls have to be set using predictive
values. There are also significant variations andfluctuations in the composition and heat value of recycled
fuel and raw materials. There is also the occurrence ofsolid/gas and solid/liquid reactions at high temperaturesin the kiln system (including the preheater and the kiln
itself). In other words, cement kilns are a system made upof elements that are difficult to control, including
significant disturbances, dead time, distributed constants,
non-linear factors and time variations. Even if an attempt
were made to use step response testing to try to ascertain
certain characteristics, it is a process with a closed loop
and slow reaction time. Testing would be very difficult
due to the effects of other variables changing during
testing and the complex effects of many different changes
in input.
Computerized control developers at cement companies
continued to battle with these processes and yielded
results. Common to all the developments by different
companies were the analysis of processes based on theanalysis of data taken from years of observing onsite
operation (human operation) and problem-solving using
an academic approach in collaborating with external
experts for joint research and theoretical corroboration.
Carrying out joint research with external experts made it
possible to expand the scope of operation to other plants
and other processes. With a robust design to handlechanges in processes and by making parameter
adjustments very similar to actual operation, it waspossible to create a long-lasting control system.
Cited reference (20) has more detail on specificexamples of control systems that were developed.

History of Cement Manufacturing Technology

60

5.7.3

Computerized Control: Current Situation in2010 and Future Challenges 4) 20)
IT technology is advancing at a rapid pace. The
following provides a brief overview of the state ofcomputerized control technology for cement
manufacturing in 2010 and the challenges for the future.
Due to increasing variety and volume of recycledresources and greater diversity in the types of coal, themain fuel source, in recent years, proper handling of thesehas become more complicated. This may have led to lessstability in the cement manufacturing process. Changes indemand have meant major changes in production volumes(e.g. producing 4,000t/d with a 5,000t/d kiln). This has
made existing control systems less stable and placed agreater load on operators. Many of the recycled resourcesthat require high-temperature disposal are disposed of in
the raw materials process and burning process. A major
challenge for the future is how to control the compositionof raw materials and combustion of fuel while utilizing
recycled fuel and raw materials to the maximum extent.
In the finishing process in cement manufacturing, theclinker being ground is a chemical product and varies
little in hardness, composition and other characteristics.
This meant it was already quite an efficient process in theage of automated control. Consequently, with theintroduction of computerized control, it has been far
easier to deal with than the raw materials process andburning process.

(1) Raw Materials Proportioning Control 21) 22) 23)
The raw materials process uses a combination of online
X-ray fluorescence analyses and computerized control. In
this regard, the late 1960s saw rapid developments in the
proportioning of raw materials and the integration ofblending silos. This significantly improved the issue ofhomogeneity, which had been the weakness of the dry
process. Thus, the wet process became a thing of the past(see 4.8).
The main method for analyzing the composition of raw
materials proportioned at plants was usually X-ray
fluorescence analysis using the glass bead method. Onoda
Cement (now Taiheiyo Cement) set up a continuous
measuring system using a special powder pressing
mechanism to manage the chemical composition of the
raw materials. However, this system was mainly for
managing trends by continuously checking variations incomposition and did not require highly accurate analysis.
Because of the development of new systems, discussed
below, this system is no longer used; however, it had
some outstanding continuous management capabilities forthe time.
In the 1990s, recycled materials began to be utilized in
the process. As these materials began to increase invariety and volume, they were added in at various stages

61in the process depending on the composition andcharacteristics of the material and the layout constraintsof the facility. As a result, the constraints on raw
materials proportioning have increased. The greatest
challenge now is how to control composition while
making maximum use of recycled materials.
The usual glass bead method of X-ray fluorescenceanalysis was accurate enough, but the process
management system was essentially manual operation,from sampling on site to transportation to the laboratory,
pre-processing of samples (crushing and melting to form
beads) and X-ray fluorescence analysis. This meant thatanalysis was limited to once every one or two hours,
which placed limitations on the consistency of thechemical composition of the raw material proportioning.
By contrast, the main method used today has
automated all of the above (on-VLWHDXWRPDWLFVDPSOHUĺ
conveying by pneumatic tXEHĺURERWLFSUH-processing
RIVDPSOHVĺ;-ray fluorescence analysis). The analysis
data obtained is automatically forwarded to the raw
material proportioning system, which performs
computerized model predictive control. The proportioning
ratio is controlled automatically for every type of raw
material. Automating everything enables more frequent
analysis than previously (for example, three to four times
per hour), thus making it possible to have closer control
over the proportioning ratio. With all of the complications
with raw materials, this has made a significant
contribution to chemical composition stability.
Most cement companies use model predictive control
for controlling the proportion of raw materials. This isbecause model predictive control is easy to implement incontrol systems with multiple inputs and multiple outputs.
It is also very robust and can handle increasing
proportions of recycled materials. Conventionally, it wasa system of feedback control, analyzing the compositionof the output proportion and adjusting the proportions tomatch target values. An additional control target has been
added: using recycled materials as preferentially as
possible within the limitations of the composition. Further
explanation of model predictive control can be found inspecialized sources.
Automated composition analysis systems for process
management are also being worked out for the burning
process and finishing process. While X-ray fluorescenceanalysis is the only tool used to analyze composition in
the raw materials process, many systems in the burning
process and finishing process also use it in combination
with powder X-ray diffraction by the Rietveld method(Note 3). This makes it possible to automatically quantify
the f-CaO (free lime, indicator of burning degree) andmineral composition of the clinker/cement at the sametime as the chemical composition. This is very useful, as
the number of operators and quality control personnel canbe reduced to take the appropriate action.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March5.8 Overview of Energy-Conserving
Technologies since 1970

1)

Cement manufacturing uses heat energy and electricalenergy. This chapter has discussed the cement
manufacturing devices and methods that have been
introduced or developed since the 1970s. The main aim
for these technologies has been energy conservation. The
following discusses how much energy has actually beenconserved as a result.
5.8.1
Trends in Heat Energy Consumption
As at 2011, the heat energy used at cement plants ismade up of around 73% coal, around 12% petroleum coke,around 14% industrial waste and byproducts, such aswaste oil and used tires, and a small amount (around 1%)
of fuel oil (heavy oil). Coal is imported from China,
Australia, Russia, Indonesia and other countries. Coal has
a calorific value of around 27-29MJ/kg when it is burnt.
Figure 5.13 shows the heat recovery and utilization in the
cement burning process today.
Clinker burning
heat
Heat used fordrying raw
materials
Combustion heat
Heat input

96%

100%

Sensible heat of raw materials,
cooling air, etc. 4%

Heat used fordrying coal
Waste heatrecovered for
power generation

Heat escaping in
the exhaust gas
Clinker residual(sensible) heat
Other

Efficiently utilized energy(3) Computerized Control Technology Development
Challenges 20)
In recent years, management has become centralized
over networks, including data collection and programmodification/correction. Using OPC communication, it
has also become possible to use operational support
systems and other software packages and development
tools.
Meanwhile, the demand for cement started to decline
even further from around 2000. Since then, there havebeen fewer instrumentation and control engineers, with
the number halved by 2010. There are even companies
now with no development engineers. This means that it is
now more difficult to achieve what was previously
accomplished by instrumentation and control engineers in
the manufacturing industry, that is, to provide theconnection between control theory and manufacturing
site.
Even with new control theories emerging, there is ofcourse no improvement in controllability if operators do
not understand it or how to apply it to processes. Even if
the effort is made to produce various new technologies
and apply them on site, it is not uncommon for these todrop unnoticed out of use in the cement industry or any
other industry. At this time of dramatic changes in usageof recycled materials, the control systems currently inplace are also likely to drop out of use if sites cannot keep
up with change.
Accordingly, there is a greater need now than ever tocreate development systems in which development isdone as efficiently as possible using software packages
and generic tools. Companies also needs to have input
from collaborative research with external experts
regarding modeling, process analysis and onsite control,with a strong need for process knowledge and operatingknow-how.

Waste energy(2) Burning Process Controls 20)
The use of recycled materials has also increased in thepreheater part of the burning process. The raw materials
pass through the preheater for several seconds, requiringcontrol cycles of seconds rather than the minute cycles inconventional rotary kiln control systems.
Since variations in recycled fuel and variations in theclosed loop part of the process have a significant
difference on the cycle, there are control mechanisms foradjusting each part of the process. Analyses are carriedout to ascertain the degree of impact of these factors,
including statistical analysis developed using a
multivariable autoregressive model. Knowledge gained
from tasks that were done manually, such as
starting/stopping the recycled fuel feed and detecting andresolving blockages, is used to optimize and automate thesystem using an operational support system software
package. These tasks were performed by DCS and PLC
until the late 1990s. However, with the increase ofalternative fuel and raw materials (AFR), it became
necessary to increase the frequency of operation andcoordinate with continuous control. Since 2000,
companies have been introducing operational support
systems.

Fig. 5.13 Flow of Heat Energy at a Cement Plant 1)

Figure 5.14 shows the heat energy consumed in cement
manufacturing (the heat energy needed to manufacture 1
ton of cement). As the figure shows, heat consumption
decreased by around 40% in the 20-year period from1970 to 1990. The main reason for this was the transition
to the superior-energy-efficient and highly productive
SP/NSP kiln systems from the wet process kilns and dry
process kilns with attached boilers, as discussed above.
By 1997, all kilns in Japan were SP or NSP kilns.
In recent years, combustible waste (alternative heat
energy source) has been utilized as an alternative to fossil
fuel in cement manufacturing. The definition of energy
History of Cement Manufacturing Technology

62given in Article 2 of the Energy Saving Act (formally the
Act on the Rational Use of Energy), does not include“energy from the combustion of waste”. Therefore, heatfrom waste sources is represented as zero in the figures
for energy consumed in cement manufacturing. The
figures including the heat from alternative waste sources
are provided for reference. In reality, it is difficult toascertain the extent to which combustible materials fromwaste contribute to the burning process as a calorificvalue.

Trends in Electric Power Consumption(kW/t-cement)

Electric power consumption

Electric power consumption
less waste heat power

Trends in Heat Energy Consumption(year)(MJ/t-cement)

Fig. 5.15 Trends in Electric Power Consumption since1970 24)

5.8.3
Including alternative waste sources

Excluding alternative waste sources(year)Note) Research on usage amount of alternative waste
sources began in 1980

International Comparison of Energy
Consumption
Figure 5.16 shows an international comparison ofenergy consumption. This is clear proof for future
generations of the brilliant history-making achievements
in production technology made by the Japanese cement
industry in producing the world’s most energy-conserving
technology.

Fig. 5.14 Trends in Heat Energy Consumption since 1970

63

China

Weighted
average

UnitedStatesCanadaBrazil

South
Korea

Spain

India

Germany

MexicoItaly

Thailand

5.8.2
Trends in Electric Power Consumption
Figure 5.15 shows the trends in electric power
consumption since 1970.
One of the ways used to effectively utilize waste heatin cement manufacturing is waste heat power generation(see 4.2.2 and 5.6). Waste heat power generation is thegeneration of electric power using heat energy fromexhaust gas. The electric power produced from waste heat
power generation is distinct from power from powercompanies and private thermal power generation. Thebase figure is calculated by subtracting the amount ofwaste heat power from the total power consumed byprocesses. The total power is provided for reference.
As shown in the figure, electric power consumption
decreased by around 20% in the 20-year period from1970 to 1990. This is the result of actively introducing
vertical mills with high grinding efficiency into the raw
materials process (see 5.4.2), grinding aids into thefinishing process (5.5.2), as well as classifying liners andsmaller balls (5.5.3), eddy current separators (5.5.4) andpre-crushers (5.5.6).
However, there has been a slight upward trend inrecent years, as increasing utilization of waste andbyproducts has meant more electricity has been needed
for handling (crushing, mixing, transporting, etc.) of thosematerials.

Japan

24)

Fig. 5.16 International Comparison of Energy Consumption
25)

Comparison of energy consumed per ton of clinker (Japan=100, 2003)
Original data from: The International Energy Agency; 2008
Electric energy converted as 1 MWh = 0.086/0.33 toe(toe: ton of oil equivalent; 1 toe = 41.8605 GJ)

Note 1: Air-Swept (Mill)In an ordinary mill, the internal airflow has slightly negative
pressure to limit external dust emissions. By contrast, theairflow in an air-swept mill is reinforced for cooling, drying andfines removal.
Note 2: OPC (OLE for Process Control)
Unified specifications for international standard
inter-application communication interfaces, formulated by the
OPC Foundation of the United States.
Note 3: Rietveld Method 21)
A method devised in 1969 by Dutch crystallographer Hugo
Rietveld for neutron diffraction. Called XRD/Rietveld whenused with X-ray diffraction. Using the XRD/Rietveld method,
the theoretical diffraction profile is refined from the X-ray
diffraction diagram using the least squares method and the
crystalline structure parameters are defined for each mineral.
This makes it possible to refine the crystalline structure. In
recent years, this method has started being used on samples of
cement and other materials containing different kinds of

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchminerals. Like the crystalline structure, the scale factor, orparameters showing the proportion of different phases, can also
be refined. This makes it possible to know how much of whichminerals are contained in a sample.

References (all in Japanese)
1) Japan Cement Association, Introduction to Cement &Concrete, 2013.
2) Nihon Cement Co., Ltd., 100-Year History of Nihon
Cement, 1983.
3) Onoda Cement Co., Ltd., 100-Year History of Onoda
Cement, 1981.
4) Mitsuhiro Ito, “R & D for Effective Cement
Manufacturing”, Journal of Research of the Taiheiyo
Cement Corporation, No. 150, pp. 29-56, 2006.
5) Tatsuo Okabe, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 41-51,1978.
6) Kanzaburo Suto and Masuo Sada, Chichibu Cement(now Taiheiyo Cement) company document “Cement
Dokuhon Vol. 4: Manufacturing Technology”, pp.
130-144, 1978.
7) Japan Cement Association, “Technologies of Energy
Saving and Resources Saving in the Japanese Cement
Industry”, Report T-22 of Committee on Cement
Manufacturing Technology, 2002.
8) Yunosuke Hayashi, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 77-83, 1978.
9) Supplied by Taiheiyo Cement Corporation.
10) Marekata Kondo, Noriyuki Watanabe and Atsuyuki
Takakura, “Operating Results of the Dopol Kiln”,
The Cement Manufacturing Technology Symposium,
No.21, pp. 33-42, 1964.
11) Toshikazu Ichiyanagi, Atsutoshi Kurotaki andTamotsu Negishi, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 96-111,1978.
12) Ube Industries Ltd., The Story of Kanichi Nakayasu,
1984.
13) Kenji Suzuki, Kazuhiro Imahashi, Tadayuki Koga

and Takao Ogiri, “Reduction of Pressure Loss inLarge-Scale Loesche Mills”, The Cement
Manufacturing Technology Symposium, No.40, pp.
62-67, 1983.
14) Ikuo Uchida, Chichibu Cement (now Taiheiyo
Cement) company document “Cement Dokuhon Vol.
4: Manufacturing Technology”, pp. 31-35,1978.
15) Shigetoshi Toyooka, Satoshi Oya and Kikuo Ogawa,“Operating Results of the Cement Mill with theHigh-Performance Separator O-SEPA”, The Cement
Manufacturing Technology Symposium, No.45, pp.
31-36, 1988.
16) Personal communication with Takamiki Tamashige,
May 26, 2015.
17) Hiroshi Obana, Koichi Sato, Takamiki Tamashige,
Kenichi Zaitsu, Toshiyuki Ueda and Masaki
Hamaguchi, “Operating Results of the Large-Scale
OK Mill for Cement Grinding”, The Cement
Manufacturing Technology Symposium, No.45, pp.
25-30, 1988.
18) Personal communication with Hiroshi Obana, August
1, 2015.
19) Takahisa Uchida, Kyoichi Shibuya, Tomikazu
Sekiwa, Yoshio Sotoya, Masao Gamo, Tomomizu
Ihara and Hiroshi Nakari, “Exhaust Gas Power
Generation in the Cement Industry”, The Cement
Manufacturing Technology Symposium, No.38, pp.
18-23, 1981.
20) Nobuo Takechi, “50 years history of the Society of
Instrument and Control Engineers, 3.3.7: Cement
Industry”, Journal of the Society of Instrument andControl Engineers, Vol.50, No.8/9, pp.640-644,
2011.
21) Taiheiyo Cement website, September 2015.
22) Takayoshi Okamura, “Cement Production and its
Relation to Persons”, Concrete Journal, Vol. 52,
No.9, pp. 759-764, 2014.
23) Personal communication with Takayoshi Okamura,
November 24, 2015.
24) Japan Cement Association, Pamphlet,“Environmentally Friendly Cement Industry”, 2015.
25) Japan Cement Association website, September 2015.

History of Cement Manufacturing Technology

64

6

Environmental Conservation Technology andMeasures against Global WarmingThis chapter discusses the following two points.
(1) In the 1970s, environmental regulations were put
in place and the cement industry had to comply
with strict enforcement. Full use of existing
technology as well as new technologicaldevelopments made it possible to meet the strict
controls.
(2) Global warming became a topic of attention fromthe 1990s onwards. The cement industry is fated tocause carbon dioxide emissions, not only throughthe combustion of fuel (fuel-generated CO2), butalso through the decarbonization of limestone(process-generated CO2). Efforts have been madein the cement industry to form internationalorganizations to jointly research countermeasures.

6.1 Development of Environment-Conserving
Technologies
The Air Pollution Control Act was established in 1968
and underwent significant amendment in 1970 at the 64th
Diet session, otherwise known as the “Pollution Diet”,
along with the creation of the Noise Regulation Act.
Meanwhile, following pollution issues with Asano
Cement’s Fukagawa plant in the early 20th century (see4.11.1), companies and plants installed electrostatic
precipitators and bag filters, as well as taking measures toprevent noise. Throughout that process, the technology
dealing with “tangible pollution” reached nearcompletion.
However, the Pollution Diet in 1970 was followed by
the enactment and later amendment of the Air Pollution
Control Act, the Water Pollution Prevention Act and otherlaws on preventing noise and vibration. As a result,people began to understand “environmental regulation” inthe broadest legal sense, that it covers more than tangible
pollution and includes nitrogen oxide emissions, sulfur
oxide emissions and heavy metals in the cement.
Most of the sulfur oxide (SOx) in the cement
manufacturing process comes from the sulfur content in
the fuel. However, since the cement kiln exchanges heat
between the exhaust gas and the raw limestone material,
the raw material captures SOx during the heat exchange
process. The SOx eventually comes out of the kiln as a
calcium sulfate compound in the clinker. In SP and NSP
kiln systems, the preheater exchanges heat between theexhaust gas and the limestone and acts as a giant

65

desulfurization unit. This has meant mostcountermeasures are no longer necessary.
By contrast, a major issue for the cement industry is
the inevitable generation of NOx with high temperature
fuel combustion. Burning clinker requires hightemperature flames of around 1500ºC in the burner,
meaning NOx generation is unavoidable. However, theNOx is not absorbed at any point before the exhaust gas isemitted from the smokestack into the atmosphere. As aresult, there have been some cases of plants having tocomply with strict enforcement. Technologicalcountermeasures for NOx are discussed in 6.1.1 below.
Cement contains very small amounts of heavy metals(such as copper, lead and zinc), for reasons discussed
later. As regulations were developed for the Water
Pollution Prevention Act and water emission standards
were adopted ready-mixed concrete plants and precast
concrete plants, wastewater from these plants began to bemonitored for heavy metals. The need arose for proper
management of heavy metals in cement. See 6.1.2 fordetails on countermeasures for heavy metals in cement.
6.1.1
Nitrogen Oxide: the NSP Trump Card 1)
Nitrogen oxide (NOx) from cement kilns is produced
as fuel is combusted in the kiln. NOx from the
combustion furnace is categorized by occurrence
mechanism as “thermal NOx”, generated as nitrogen in
the air oxidizes during combustion, and “fuel NOx”,
generated as trace amounts of NOx in the fuel are
combusted (oxidized). Most of the NOx from cementkilns is thermal NOx generated by high temperature
combustion.
As at 2014, the national NOx emission standard for
cement kilns was 480ppm (O2: 10% conversion) for
facilities predating 1975 and 250ppm for new facilities
built since 1975. However, there are also cases ofadditional regulation according to local bylaws. In 1977,
when the NOx regulations for cement kilns wereannounced, some plants and kilns were identified as
exceeding 480ppm.
The NOx occurrence mechanism in cement kilns is dueto the interaction of three factors: (1) the maximum
temperature of the combustion flames, (2) the duration at
maximum temperature and (3) the combustion air ratio.
These three factors are also important for burning highquality clinker. One of the toughest challenges for cement
plants has been that compliance with NOx regulations is

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchat odds with producing high quality cement. Companies
have worked hard to comply with NOx measures in orderto survive, while the industry has worked on initiatives
such as joint development of low-NOx burners. As aresult of these efforts, the following NOx-reducing
measures have been found to be effective.
1) Conversion to NSP: Combustion is separated
between the rotary kiln and the calciner, thus
reducing NOx by lowering the fuel ratio of therotary kiln, which requires a high temperature
range.
2) Use of low-NOx burners: An improved burner
structure that (1) stabilizes and enlarges the NOx
reduction area in the flame, and (2) ensuresuniform pulverized coal spread and final burnout
performance.
3) Elaborate operation management: Using the NOxreading at the furnace outlet as the performanceindicator. If the NOx reading is high, working to
reduce the NOx by adjusting the burner flame orusing low air ratio combustion.
4) Utilizing waste material with denitrification(reduction) effects, such as biosolids.
5) Addition of denitrification agents: Adding agents
such as ammonia or urea to the high temperature
gas in the preheater.
Ultimately, at the present time, all companies haveadopted full measures for 1), 2), 3) and 4) according totheir own situations. Some are using 5) for any NOx in
excess of the regulated readings. As at 2014, all cementkilns in Japan were SP or NSP, with NSP systems
accounting for 83% of the total number of kilns and 86%of the production capacity.
6.1.2
Heavy Metals in Cement
The raw materials in cement are limestone, which has
basic properties, and clay, which has acidic properties.
The main components of clay are silicon dioxide SiO2,
aluminum oxide Al2O3 and ferric oxide Fe2O3. Slag (fromcopper or similar) is used as a source of Fe2O3 to adjust
the ratio between these three components. Sometimes, theslag can contain trace amounts of heavy metals (such aslead or chromium), which remain in the cement productafter the burning process.
In the 140-year history of the Japanese cement industry,
there have been no reports of heavy metals in cement
having a harmful effect on humans. However, as
regulations were developed for the Water Pollution
Prevention Act in the 1970s and water emission standards
were adopted ready-mixed concrete plants and concrete
products plants, wastewater from these plants began to bemonitored for heavy metals. This is because there is apossibility that the heavy metals in cement could leachinto the wastewater from cleaning up leftover concrete or
into the water used to clean the floors and facilities atready-mixed concrete plants and precast concrete plants.
Cement is also used for improving soft ground andstabilizing landfill waste. Accordingly, improved soil
from earth mixed with cement must be certified ascomplying with regulations on heavy metals in the soil.
Thus, cement companies have had to carefully manage
heavy metals in the cement.
There are three main points for heavy metal
countermeasures:(1) Heavy metals brought into the manufacturing
process remain contained in the cement produced.
(2) Accordingly, limiting the amount coming in also
reduces the amount coming out.
(3) The presence of heavy metals has very little effecton the quality of the cement (strength or setting).
Given the above, companies have dealt with the matterby setting voluntary standards for the amount of heavy
metals contained in incoming raw materials so that noproblem will occur.
With the aim of becoming an industry that contributes
to resource recycling, active efforts have been made toincorporate various kinds of industrial waste andmunicipal solid waste as alternative raw materials andfuel sources. The issue of heavy metals has become amajor issue for cement companies, requiring active rather
than passive efforts. Technology development hascontinued in that direction. This is discussed further in
Chapter 8.
6.1.3
Use of Bag Filters for Kiln Exhaust Gas
In the past, electrostatic precipitators (EPs, Cottrell
precipitators) were used for dealing with kiln exhaust gas
at cement plants. In recent years, there have been issues
with interrupted operating stability and deterioration with
EPs as the variety and volume of recycled materials used
as fuel and raw materials has increased, with increasing
risk to plant operation. Meanwhile, the use of low-heat
power generation has dropped the final exhaust gas
temperature to around 100ºC. Along with thedevelopment of aramid fiber and other heat-resistantfibers, this has created the conditions necessary to use bag
filters for kiln exhaust gas. In 2005, Taiheiyo Cement
improved plant operation by dismantling and removing
the existing EP at its Kumagaya plant and converting tobag filters. After that, the use of bag filters for treatingkiln exhaust gas has steadily spread throughout theindustry.

6.2 Measures against Global Warming 2)
The Earth Summit held in June 1992 prompted anincrease in global awareness of the issue of global
warming. In Japan, various initiatives commenced in theindustrial, transportation and civic affairs sectors to

History of Cement Manufacturing Technology

66

Measures to Reduce Greenhouse Gas(CO2) Emissions
In 2014, the amount of CO2 generated in the
manufacture of Portland cement at cement plants in Japanwas 0.73 kg-CO2/kg-cement. This was generated from:(1) fuel combustion (around 45% of CO2 emissions) and(2) limestone decarbonization (around 55%). At present,
the cement industry has taken the following technicalmeasures to reduce these emissions.
(1) Thorough energy conservation(2) Utilization of decarbonized calcareous waste as araw material(3) Utilization of biomass (plant-based) waste as afuel source(4) Utilization of blended cement(5) Utilization of additives(1) Thorough Energy Conservation
As previously mentioned, there have been constantefforts on this matter since the dawn of the industry, withparticularly notable progress in energy conservation sincethe 1970s. Energy consumption is ranked among the bestin the world, as discussed in 5.8.
(2) Utilization of Decarbonized Calcareous Waste asa Raw Material(3) Utilization of Biomass (Plant-Based) Waste as aFuel Source
Technological developments for items (2) and (3) are
discussed in Chapter 9. In many cases, this utilization islimited by some of the constraints below.
(i) The volume produced is often limited(ii) The area of utilization (acquisition) is often limited(iii) The chemical composition of the waste material
can also limit the amount used
However, like (1) energy conservation, waste
utilization is also linked to saving cement manufacturingcosts. Technological developments to increase thisutilization will definitely continue in the future.

67

Emissions

6.2.1

Let us turn our attention to reducing CO2 emissions byusing combustible waste as an alternative fuel source forcement plants. Waste plastic is made from fossil fuels andcombusting it increases CO2. In that sense, it is different
from biomass and other carbon neutral waste. However,using waste plastic and other combustible waste as analternative fuel source for cement manufacturing
produces less CO2 than incinerating it. The reason for thisis shown in Figure 6.1. When combustible waste isincinerated, it simply releases CO2 into the atmosphere. If
it is utilized in the burning process at cement plants, theheat produced by the waste can serve to replace some of
the fossil fuel energy (of course not all of it). The CO2
emissions from the cement plant remain the same, but theoverall CO2 emissions are reduced.

Input

implement Kyoto Protocol reduction targets. In the
cement industry, the energy conservation policies that had
been worked on as a means of reducing manufacturingcosts clearly resulted in reduced combustion-generated
CO2 emissions. However, the challenge for the cement
industry was process-generated CO2 produced in thelimestone decarbonization process. Cement industry
initiatives against global warming on this basis are
outlined below. Greenhouse gases produced during
cement manufacturing are almost entirely CO2. Other
greenhouse gases are generated in such trace amounts thatthey are scientifically negligible.

Waste

Heat energy fromfossil fuels

Incinerator

Cement plant

Incinerating waste andmanufacturing cement at cement
plants

Waste

Heat energy
from fossil
fuels

Cement plant
Utilizing alternative waste sourcesin cement manufacturing

Fig. 6.1 Reduction in CO2 Emissions by Using Alternative
Waste Sources in Cement Manufacturing 2)(4) Utilization of Blended Cement
Chapter 8 discusses the types and content of blended
cements in the JIS standards. Since this cement is made ofa blend of Portland cement and blast furnace slag or fly
ash, the CO2 emissions per ton of cement are reduced as
far as the proportion of admixtures blended in.
Cement companies around Japan have a supply system
in place for blended cement. However, the customer
decides which cement to buy and use. In 2012, blended
cement (blast furnace slag cement, silica cement, fly ash
cement) accounted for around 25% of all cement
produced. Figure 6.2 shows the trends in the blended
cement production ratio.
Waste disposal is becoming a significant revenue
stream for the Japanese cement industry. Companies andplants are incorporating waste products as fuel and raw
materials as much as they are able to without affecting thequality of the cement. Consequently, provided that: (1)there is no growth in demand for cement, (2) the level ofwaste disposal technology remains the same, and (3) the
proportion of blended cement increases, an environmental
trade-off relationship will occur, in which there will be anegative impact on the amount of waste disposed at
cement plants, incinerator disposal will increase and thelifespan of landfill sites will decrease.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchform from the 1990s onwards. Below are two
representative examples of this international
collaboration.

Year

Fig. 6.2 Blended Cement Production Ratio Trends 3)

Developments in waste disposal technology in the cement
manufacturing process are an important initiative as acountermeasure against global warming.
(5) Utilization of Additives
One genuine effort against global warming by theJapanese cement industry when the JIS standards wererevised in 1979 was adding up to 5% of additives toPortland cement in keeping with industry demand. Fourtypes of additives were approved in the JIS standards:
blast furnace slag, fly ash, siliceous admixtures andlimestone. This made it possible to reduce CO2 emissions
by up to 5% per ton of Portland cement manufactured.
6.2.2

Global Cooperation Initiatives by the
Cement Industry to Reduce Greenhouse
Gas Emissions
Cement industries in different countries joined forces
to face the following global warming issues:(1) The cement industry is an energy intensive
industry.
(2) The cement manufacturing process produces not
only fuel-generated CO2, but also CO2 fromlimestone decarbonization.
While global warming is a global issue that affects theentire world, government policies against it vary greatly
due to each country seeking to protect and foster its own
industries. Policies also differ between developed anddeveloping nations. Similarly, companies in the cement
industry vary in scale from so-called multi-national
corporations to local manufacturers with one plant. Plants
also vary in location from urban areas to remote deserts,
and in production scale, from a thousand tons per year toseveral hundred thousand tons per year.
Given this situation, efforts were made at international
collaboration with common awareness of common issues
regarding global warming in relation to the cement
industry. A number of international connections began to(1) Asia-Pacific Partnership on Clean
Development and Climate (APP) 2)
The APP was proposed by the United States in July
2005 and entered into by Japan, the United States,
Australia, China, Korea and India. The partnership waslaunched with government and private participants fromeach country, with the aim of combatting environmental
issues, energy security and climate change by developing
and sharing clean, efficient technology. In October 2007,
Canada joined as the seventh participating country. Under
the APP, governments and industries worked together on
issues related to the growing demand for energy, air
pollution, energy security and greenhouse gas.
Of the eight sectors taking part, the cement sector was
hosted by Japan. The Cement Association teamed up withthe government (Ministry of Economy, Trade andIndustry) to introduce energy-saving technologies andexplain how to calculate CO2 emissions from cement
plants to the developing countries participating in the
APP.
The APP ceased its activities in April 2011, but theJapanese cement industry adopted a policy of contributing
to the reduction of energy used in cement manufacturing
around the world and to the establishment of a
resource-recycling society. It promised to publicize (1) its
energy usage for cement manufacturing, (2) its
energy-saving technologies (facilities) and (3) its waste
utilization.
(2) The World Business Council for Sustainable
Development (WBCSD) and the WBCSD
Cement Sustainability Initiative (CSI) 4)
Taiheiyo Cement, Japan’s largest cement company, hastaken an active role in planning the activities of the World
Business Council for Sustainable Development(WBCSD) and the Cement Sustainability Initiative (CSI),
launched in 1999 as an industrial committee of the
WBCSD. It has joined forces with cement companies
around the world to promote initiatives for sustainable
development in the cement industry to handle social andenvironmental issues effectively.
The following guidelines (recommended criteria forcompliance by cement companies worldwide) provide asummary of the actual results achieved by the CSI to date.
(1) CO2 and Energy Accounting and ReportingStandard for Cement Industry(2) Guidelines for Co-Processing Fuels and Raw
Materials in Cement Manufacturing
History of Cement Manufacturing Technology

68

(3) Health and Safety in the Cement Industry:
Guidelines for Measuring and Reporting(4) Health and Safety in the Cement Industry:
Examples of Good Practice(5) Guidelines for Emissions Monitoring andReporting in the Cement Industry(6) Environmental and Social Impact Assessment(ESIA) Guidelines(7) Guidelines on Quarry Rehabilitation
The main achievement in relation to global warming
has been (1) “Cement CO2 and Energy Protocol: CO2 andEnergy Accounting and Reporting Standard for the
Cement Industry”.
The burning process is not the only source of CO2
emissions from cement industry activity. CO2 is emitted
by mining machinery during the mining of raw materials
and by transportation as the cement is transported fromthe plant to the customer. CO2 is emitted at the electricity
source. It is emitted when purchased raw materials (suchas slag or gypsum) are manufactured and when they aretransported. It is extremely wide-ranging. Accordingly,
the cement industry established the accounting andreporting standard to determine the criteria for boundaries
and calculation methods so that companies could
calculate the CO2 emissions associated with theiractivities. This made it possible for any cement company
in the world, from multi-national companies to local
manufacturers, to easily calculate their own CO2

69emissions using the same criteria, which also made it
possible to compare the figures published by eachcompany. This system established the calculation
methods used by companies around the world forreporting emissions to governments and for setting CO2
reduction targets.
Although Taiheiyo Cement is Japan’s only member of
the CSI, it is in reality an accurate representation of theJapanese cement industry. It shares the CSI matters fordiscussion and points of agreement with the othercompanies in Japan through the Japan Cement
Association.

References
1) Ministry of the Environment website, Technologies
for Controlling NOx Emissions and Operational
Management Technologies in the Cement Industry,
November 2015.
http://www.env.go.jp/en/water/wq/ine/pdf/
tool/3_guideline-fixed%20sources-jp.pdf
2) Japan Cement Association, Introduction to Cement &Concrete, 2013.
3) Japan Cement Association website, October 2015.
4) Taiheiyo Cement Corporation website, June 2015.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

7

Advances in Cement Chemistry

Consistently producing good quality products has
always been the unchanging mission of not only the
cement industry, but the manufacturing industry overall.
This report on the history of cement manufacturing
technology has mainly discussed technologicaldevelopments for the purpose of consistent production in
Chapters 2 through 5. However, in order to produce goodquality cement, knowledge of cement chemistry andwisdom based on that knowledge play an important role.
This chapter discusses the developments in cement
chemistry from the invention of modern cement to thepresent day, while Chapter 8 outlines the development
history of functional cement, that is, the diversification of
cement types. Chapter 9 leads into the industry’s
progression towards becoming a core industry in aresource-recycling society. The development offunctional cement, or the technology to dispose of waste
in the cement burning process, was made possible by firsthaving a foundation in cement chemistry.
In terms of academic disciplines, cement chemistryspans a very broad range of related fields. It encompasses
inorganic chemistry as well as synthetic chemistry and isalso strongly linked to analytical chemistry. There aremany fields that focus on mineralogy and crystallography,
as well as rheology. Of the wide range of fields that makeup cement chemistry, this report focuses on cement
chemistry that is directly cement manufacturing
technology.
Japanese researchers began submitting papers tointernational journals and similar in these fields fromaround the 1930s. World-leading Japanese researchersbegan to emerge successively from around the 1960s.
There are two main categories of reactions in cement
chemistry: the burning chemical reaction and thehydration reaction.

process of cement reacting with water and hardening is ahydration reaction. The main topics of cement chemistryresearch are the hydration reaction process and thecharacterization of hydrates.
This chapter provides a simple introduction to the basic
details of the burning chemical reaction, the hydration
reaction and their reaction products within the scopenecessary for understanding cement manufacturing
technology. Assuming this basic knowledge, this chapter
outlines advances in cement chemistry from the inventionof modern cement to the present day.

7.1 Burning Chemical Reaction and Clinker
Minerals
7.1.1

Chemical Changes in the Burning Chemical
Reaction Process 1) 2)
Table 7.1 shows the average volumes (2011) of raw
materials (raw material consumption) needed to
manufacture one ton of ordinary Portland cement.
Table 7.1 Raw Material Consumption 1)

Unit: kg
Limestone
Clay
SilicaIron-oxide etc.
Gypsum
Total

1,191
223
75
27
39
1,555

1) Burning chemical reaction: important researchfor “manufacturing” cement
A chemical reaction carried out during the burning ofground and proportionately mixed raw materials of
limestone and clay at 1400-1500ºC. The burning chemical
reaction is a solid phase reaction with a partial liquid
phase. The main topics of research are the solid phasereaction at high temperatures and the characterization ofminerals contained in the clinker formed as a result of thereaction (see Note 1).

The powdered raw materials are burned in a rotary kiln
after having been proportioned, dried and ground at fixedratios, then sent through a preheater (SP/NSP). The
burned clinker is cooled in a clinker cooler (see Chapter
5).
During the process from preheater to kiln to cooler, thecompounds in the raw materials undergo gradualchemical changes with the increase in temperature until
finally becoming the required chemical compound. Figure
7.1 shows the process of this change.
Large volumes of 3,000 to 10,000 tons of raw materials
are burned per day at high temperatures. To produce goodquality cement from the finished clinker requires accurate
proportioning technology and temperature control
technology. Ensuring a consistent high quality productrequires a round-the-clock production management
system.

2) Hydration reaction: important research for“utilizing” cement
Cement obtained by mixing and grinding clinker witharound 3% gypsum hardens when mixed with water. The

7.1.2
Clinker Minerals 1) 2)
Optical microscopy of burned and cooled clinker
reveals the granules are a variety of mineral aggregatesaround 10-ȝPLQVL]H )LJXUH 
History of Cement Manufacturing Technology

70Heating temperature(ºC)(Main chemical changes)

Fig. 7.2 Clinker Photomicrograph 3)(A: alite; B: belite; I: interstitial phases)

Evaporation of moisture adhering to raw materials
Dehydration evaporation of crystalline water in clay
Decomposition of MgCO3 (MgO + CO2)
Decomposition of CaCO3 (CaO + CO2)
2CaO·SiO2 formation begins
7UDQVLWLRQWRȕā&D2ā6L22
Formation of 3CaO·Al2O3; formation of 4CaO·Al2O3·Fe2O3
Formation of 3CaO·SiO2 (melting of Al2O3, Fe2O3, Na2O)

(1)
Alite
C3S (tricalcium silicate) is a crystal solid
solution (see Note 3) containing trace amountsof Mg, Na, K and Fe. It is the most important
In the cooling process, at near 1200ºC, melted Al2O3 and Fe2O3 form
compound in Portland cement. Ordinary
Cooling
3CaO·Al2O3 and 4CaO·Al2O3·Fe2O3. The following four compounds
are ultimately produced; these mix together as dark granules. The
Portland cement contains around 50% alite. It
dark granules are called clinker.
has a high hydration rate and shows good
Final clinker constituent compounds
3CaO·SiO2(alite C3S)
strength development from 1-day to 28-day in(belite C2S)
2CaO·SiO2
age DJHĺVHH1RWH ,WDOVRUHOHDVHVDORWRI
3CaO·Al2O3(aluminate phase C3A)
4CaO·Al2O3·Fe2O3 (ferrite phase C4AF)
heat in hydration.
Appears under microscope as columnar or
hexagonal-plate-shaped colorless crystals aroundFig. 7.1 Chemical Changes in the Burning Process 1)
10-ȝPLQVL]H )LJXUH$ 
There are four main minerals (chemical compounds)
that make up the clinker: alite (Figure 7.2 A), belite (B),aluminate phase and ferrite phase. Combined, these aretermed “clinker minerals”.
Alite and belite are both calcium silicate and accountfor 70-80% of the clinker. Aluminate phase and ferrite
phase are also called “interstitial phases” (I in the figure)because they serve to fill the gaps between the other two
compounds. These account for 15-18% of the clinker.
Table 7.2 shows the chemical formulas of thesecompounds. Formulas shown in () are uniqueabbreviations used in cement chemistry (see Note 2).
Table 7.2 Chemical Compounds in Clinker 1)
Structural chemical compounds
in clinker
alite
calcium silicate
beliteinterstitial
phasesaluminate
phase
ferrite phase

Chemicalformula
3CaO•SiO2(C3S)
2CaO•SiO2(C2S)
3CaO•Al2O3(C3A)
4CaO•Al2O3•
Fe2O3(C4AF)

Comments*
Contains trace amounts ofaluminum, iron,magnesium, sodium,
potassium, titanium,
manganese, etc.
Contains trace amounts ofsilicon, magnesium,
sodium, potassium, etc.

*Each compound usually contains other compounds as listed in the comments
column.

These four chemical compounds have different
characteristics, as mentioned below. Cement is developed
for different purposes by altering the composition ratio of
the clinker. This is discussed in Chapter 8. The following
is a brief discussion of the characteristics of eachconstituent mineral in clinker.

71(2) Belite
C2S (dicalcium silicate) is a crystal solid solution
containing trace amounts of Mg, Na, K and Fe. Ordinary
Portland cement contains around 30% belite. It has alower hydration rate than alite and takes longer to reachfull strength, but releases less heat in hydration.
Appears under microscope as pale yellow or lightbrown clumps around 20-ȝPLQVL]H )LJXUH% Alite and belite are both more active in hightemperature transformation (see Note 5) than low
temperature transformation. Both also have good
hydration and strength development. Accordingly, it isimportant to burn as long as possible at high temperatures
to increase high temperature transformation and then cool
the clinker to prevent the transition to low temperaturetransformation (see Note 5). This is an important point for
manufacturing technology and an important role for theclinker cooler.
(3) Aluminate phase
Aluminate phase is one of the minerals that make up
the interstitial phase in clinker. It is a solid solution
containing Na, K and Mg and has a chemical makeup
very close to C3A (tricalcium aluminate). It reacts very
quickly with water and instantaneously sets while
releasing a lot of hydration heat. Gypsum is added as asetting regulator to inhibit this instantaneous reaction (see7.5.1). Aluminate phase affects setting, 1-day strengthand hydration heat.
Ordinary
Portland cement
contains around
10% aluminate
phase, althoughsome products,

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchsuch as moderate-heat Portland cement, for use in dams
or other mass concrete applications are produced with lessaluminate phase to control hydration heat (see 8.3.1).
Aluminate phase also reacts with sulfate to produce
expansive ettringite (see 7.5.1 (2) and Figure 7.4). Thisdegrades the composition of the concrete or mortar andcauses the structure to deteriorate. Therefore, companies
are also producing sulfate resistant cement, which has lessaluminate phase to improve sulfate resistance (chemical
resistance) (see 8.3.1).
(4) Ferrite phase
Ferrite phase is one of the minerals that make up theinterstitial phase in clinker. It is a solid solution
containing Na, K and Mg and has a chemical makeup
very close to C4AF (tetracalcium aluminoferrite).
Ordinary Portland cement contains around 10% ferrite
phase. While it has very little impact on the cement
hydration reaction (setting, strength), it plays very
important role in the burning process, as it forms a liquid
phase and promotes chemical reaction. In other words,
ferrite phase contributes more to energy conservation
during manufacturing than it does to cement quality. The
light gray color of cement powder is also mainly due toiron in the cement. White cement is cement that contains
very little iron or ferrite phase.
(5) Other minerals in clinker
Observation of clinker under microscope reveals otherminerals, such as (1) free lime (f-CaO) or (2) alkali
sulfate ((Na,K)2SO4), depending on the raw materials andburning conditions.
f-CaO is unreacted quicklime. Clinker burned normallycontains less than 1% f-CaO. Since quantitative analysis
of f-CaO can be easily performed by chemical analysis or
instrumental analysis, it has been used as a quick meansof determining the quality of the clinker on site.
7.1.3

Moduli for Controlling Cement Composition
Proportion 4) 5)
As already mentioned, the typical chemical structure of
cement (clinker) includes SiO2, Al2O3, Fe2O3 and CaO.
Varying the mixing ratio of these four compounds candirect most cement properties, such as clinker burning
conditions, end-product cement strength, hydration heatand drying shrinkage. Consequently, cement plants
mainly control the proportioning ratios of these four
compounds in the cement raw materials.
In this sense, it is more efficient and effective tomanage the quantitative ratios between the four
compounds than to adjust and manage the amounts ofthese individual chemical compounds separately.
Accordingly, three indicators called moduli are used tocontrol the chemical composition of the raw materials.
The target moduli are set according to the types andproductivity (burnability, grindability) of the cement
product to be manufactured, and then the proportion of
raw materials is regulated to maintain these. The threemoduli are managed together because there are four main
compounds. The unit weight of each raw material can be
determined by the solution to a four-variable
simultaneous equation, using the values of each modulus
and the condition that the total mass after burning is 1 ton.
Table 7.3 shows the moduli currently used by cement
plants to manage the composition of Portland cement.
Explanations are given below.
Table 7.3 Moduli for Regulating Cement Composition 4)
Name

Chemical formulaHydraulicmodulus
Silica modulus
Iron modulus

Activity index
Lime saturation
degree(1) Hydraulic Modulus (HM)Of the four main compounds in Portland cementclinker, CaO is basic and the other three (SiO2, Al2O3 andFe2O3) are acidic. In other words, the clinker burningchemical reaction is a salt formation reaction between
acid and base at high temperature. The hydraulic modulus
represents the ratio between the amount of acids andbases and is the most important of the cement moduli.
High HM raw mix generally require high burningtemperature and adequate time, thus consuming more fuel.
Insufficient burning can often lead to unreacted free lime
remaining in the clinker. Since high HM cement is high in
C3S, it tends to have high early strength and highhydration heat.
Ordinary Portland cement clinker in Japan is currently
produced with a HM value of 2.0-2.2.
(2) Silica Modulus (SM)A ratio representing the quantitative relationshipbetween acidic compounds. A high silica modulus meansa lower amount of liquid phase to aid the burningchemical reaction and requires a higher burningtemperature. This can damage the kiln lining as a result.
However, high SM clinker is lower in interstitial phases
and higher in belite, which produces cement that is low inheat generation and superior in late-age strength.
Conversely, low SM means high liquid phase content,
which can build up the coating on the interior wall of theHistory of Cement Manufacturing Technology

72kiln, causing concern over obstructing the flow of raw
materials (coating trouble).
Ordinary Portland cement clinker in Japan is currently
produced with a SM value of 2.4-2.8.
(3) Iron Modulus (IM)The ratio representing the quantitative relationshipbetween Al2O3 and Fe2O3. Raw mix with low IM caneasily produce clinker minerals even when burned at low
temperatures. Due to the low amount of C3A and highamount of C4AF, the cement has low early strength, but
low hydration heat and high sulfate resistance. By
contrast, high IM cement has more C3A and hardens more
rapidly. Consequently, it has high early strength, but highhydration heat and low sulfate resistance.
Ordinary Portland cement clinker in Japan is currently
produced with an IM value of 1.9-2.1.
(4) Activity Index (AI)Most cement plants in Japan manufacture cement bymanaging HM, SM and IM. However, some use theactivity index (AI) instead of SM, while others control the
Fe2O3 amount rather than using the IM.
Ordinary Portland cement clinker in Japan is currently
produced with an AI value of 3.8-4.2.

developing new types of cement. Some plants also use
LSD instead of HM.
The standard LSD value of ordinary Portland cementclinker currently produced in Japan is 0.92-0.96.

7.2 Hydration and Hydrates 1) 2)
Cement with water added and well mixed in is called
cement paste (see Figure 1.1). If left in this state, cement
first becomes moldable like clay, but then graduallyhardens with time so that molding becomes more difficult.
As more time passes, it finally sets hard. This is because
the compounds in cement react with water to form newcompounds called hydrates. The chemical reaction
between cement and water is also called hydration. The
process of cement paste gradually becoming harder andmore difficult to mold is called setting, while the processof set cement becoming even harder is called hardening.
Figure 7.3 shows the process concept of cement
reacting with water to form hydrates. The figure shows
how hydration begins on the surface of the cement
particles that come into direct contact with the water. As
the reaction progresses, the unreacted portion grows
smaller. The cement particles are covered over by thehydrate product, which binds together and hardens.

(5) Lime Saturation Degree (LSD)

Cement particles(from H.F.W. Taylor, The
ChemistryofCement, Vol. 1, 1964)

The chemical compound values for the moduli (1) to(4) above are simply the percent by weight figures for thechemical compounds in the clinker. They do not take theacid/base chemical equivalent into allowance. In that

Hydrates
Directly after
mixingUnreacted
portionsense, they are practical ratios or indicators for simple
process control and have little chemical significance.

After several
hours

By contrast, the lime saturation degree (LSD) is a ratio
based on the chemical equivalence of the respective
compounds contained in each clinker mineral phase.
This formula calculates the maximum CaO (saturatedCaO) amount that can bond with the acid component. The
coefficients for the compound denominators were first
proposed by Hans Kuhl (Germany) and explored further
by later researchers. The coefficients used currently were
determined based on research by F.M. Lea and T.W.
Parker (UK).
CaOmax = 2.8SiO2 + 1.2Al2O3 + 0.65Fe2O3
When a raw mix with an LSD near 1.0 is fully reacted,
all of the SiO2 turns into C3S, producing high earlystrength clinker. By contrast, burning a low LSD mix
produces slow strength development clinker that is low in
C3S and high in C2S.
LSD is used for setting compound ratios when73

After several
days

Fig. 7.3 Portland Cement Hydration Process 1)

Understanding about hydration and hydrates is very
important when using cement. Ready-mixed cement
plants measure and mix cement, gravel, sand, water andother additives, transport it to construction sites by mixer
truck and pour it into formwork on site. The cement
setting time and early stage hydration ensures time for theconcrete to be transported and worked.
The poured concrete hardens with time. Once it has
hardened to a certain point, the next scheduled task canproceed. For example, if it is a concrete foundation,
things can be erected on top of it and machinery can beinstalled. The time until the concrete can begin to be used
is determined by the strength development of the cement,that is, the cement hardening time.
Thus, from the perspective of using cement, theNational Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchimportant qualities are:are the quickest to react. Aluminate phase is especially(1) having a consistent setting time that is with aquick to react and can set within a matter of minutes

user-friendly range(flash setting). This can cause the mortar or concrete to(2) having an adequate and consistent strength

set while still being worked.

development

To inhibit this flash setting, around 3% gypsum is

It is obvious that knowledge of hydration and hydrates

added to the clinker when it is ground into cement.

is extremely important to cement manufacturers andGypsum dissolves in water and reacts with aluminate

users.

phase to produce a compound called ettringite (see Figure

Hydration is an exothermic reaction, releasing the heatof hydration. This is discussed in 7.3.

7.4). The ettringite covers the aluminate phase, thereby
preventing the aluminate phase from coming into contact

Figure 7.4 shows the basic reaction formula for cementwith the water, thus slowing down the speed of hydration.

hydration. Cement hydration is an extremely complex

Setting is delayed from several minutes without gypsum

chemical reaction in which multicomponent solids called

to several hours with gypsum added.

clinker minerals react after dissolving in a liquid phase

Meanwhile, like aluminate phase, alite phase also has a(water) and then precipitate as new tiny multicomponent

very quick initial reaction, but temporarily slows down

hydrateV ȝPRUOHVV $IXOOH[SODQDWLRQZRXOGUHTXLUH

later hydration. Although there are various theories ona very lengthy description. This report focuses on thewhat causes this delay mechanism, it is not yet fully

necessary scope for understanding cement manufacturing

understood.

technology, as per the discussion on hydration andTesting methods for setting are regulated by JIS R

hydrates below.

5201 Physical Testing Methods for Cement. JIS R 5210

It should be noted that Figure 7.4 shows the formation

Portland Cement stipulates that the initial setting for theseof Ca(OH)2 as one of the alite/belite hydrate products.

testing methods is “60 minutes or more”, when stiffness

The presence of this Ca(OH)2 makes the hardened form of

begins, and the final setting is “within 10 hours”, when it

cement (mortar and concrete) basic.

can no longer be molded. Ordinary Portland cement on

7.2.1

the market today is designed to have the initial setting at

Early Hydration and Setting Stagearound two and a half hours and the final setting one hour

The four types of clinker minerals (compounds)
discussed in 7.1.2 start to chemically react immediately

later.

on contact with water. Alite C3S and aluminate phase C3A

water

Clinker minerals

hydratesnCaO·SiO2·mH2O(calcium silicate hydrate)[n§1.2~2.0]
Ca(OH)2 (calcium hydroxide)(alite)(belite)(gypsum)(aluminate phase)(ferrite phase)(ettringite)(ettringite)(monosulfate hydrate)(calcium aluminum hydrate)

Like the reaction with 3CaO·Al2O3, hydrates can be
represented in the form of partially dissolved Fe2O3
and Al2O3 replaced by (Al2O3)×(Fe2O3)1-x.

Fig. 7.4 Cement Hydration 1)

History of Cement Manufacturing Technology

74

7.2.2

Strength Development and Hardening
Stage
The process from cement setting to hardening involves
hydrates formed by hydration binding
three-dimensionally and becoming denser as areas wherewater and air are present become filled. As it ages, it
becomes denser and harder, thus developing the strengthof cement and concrete.
Hardening is complete once the respective minerals
that make up the clinker have finally formed hydrates.
Hydration of cement particles usually begins on thesurface and it can take a long time to fully hydrate.
However, the particles do not have to be fully hydrated
when the hardened substance exhibits the required
strength. Hydrates on the surface of cement particles
should form strong, physical, three-dimensional bonds
with nearby hydrates. Accordingly, in terms of hydration,
it is sufficient that water penetrates cement particles to acertain depth from the surface to produce hydrates.
However, the amount of water added to cement atconstruction sites is not generally determined by theamount needed for hydration, but by the amount needed
to produce the appropriate softness (consistency) for use
at the construction site. As a result, the amount of waterused in concrete is usually more than the amount needed
for cement hydration.

7.3 Heat of Hydration 1)
The chemical reaction between cement and water toproduce hydrates is an exothermic reaction. The total
amount of heat generated from the time the cement ismixed with water to a certain point in age is referred to as
the heat of hydration at that age.
The amount of hydration heat varies depending on (1)the mineral composition (chemical composition) of thecement, (2) the fineness of the cement particles and (3)the amount of water mixed with the cement. The mostimportant of these factors is (1) the clinker mineralcontent.
The heat of hydration has both positive and negative
effects on the concrete. For example, in cold climates,
concrete is wrapped in heat insulated material when it ispoured and the heat generated from hydration is used as ameans of insulated curing. By contrast, in mass concreteused in dams and large piers, the elevated temperaturefrom the heat of hydration creates a temperature
difference between the surface and the internal area andcan lead to cracking (temperature cracks). Consequently,
low hydration heat cement has been developed for massconcrete (see Chapter 8).
JIS R 5203 Testing Methods for Heat of Hydration of
Cement regulates the methods for testing the heat ofhydration of Portland cement. Ordinary Portland cement
tested using those methods has a hydration heat of75

318-336J/g at 7 days and 370-396J/g at 28 days.

7.4 Advances of the Cement Chemistry on the
Burning Process and Clinker Minerals“Ancient cement” used at sites dating to the Neolithic
period was used for several thousand years throughout
Ancient Egypt, Greece, Rome and China, up until the
Industrial Revolution. It developed very little as amaterial, always made from mixtures of local materials
and never going beyond the passing down of traditions byartisans (see 2.1).
Cement chemistry research based on scientific methods
began in the mid-18th century, following the invention of“hydraulic mortar” by John Smeaton (UK) (see 2.2). At
the time, the only research methods available were wet
chemical analysis and optical microscopes. However,
early researchers proposed bold hypotheses on chemical
reactions of the burning process and clinker minerals
based on close observations and devoted their efforts toempirical demonstration.
In the 20th century, the development of various analysis
instruments, such as X-ray diffractometers and electron
microscopes, made it possible to accurately observe,
measure and analyze clinker mineral crystalline structuresand hydrate microstructures. Cement chemistry research
expanded rapidly in breadth and depth.
7.4.1

Chemistry of the Burning Process andClinker Minerals: Advances to the Late 19th
Century 5) 6) 7) 8)This section discusses the development history of“cement chemistry as cement manufacturing technology”
during the 150-year period from the invention of modern
cement in the mid-18th century to the end of the 19th
century, focusing on the chemists who made significant
contributions to cement chemistry.
(1) John Smeaton (UK) invented “hydraulic mortar” in
1756, as mentioned in Chapter 2. Since it would havebeen difficult to achieve high temperatures with theburning technology of the time, the burningtemperature is estimated to have been low, at around
1000ºC. Consequently, in light of what is known incurrent cement chemistry, the so-called cement(clinker) minerals would probably not have formed.
However, the SiO2 and Al2O3 in the clay would
probably have been activated by the calcination
effect and increased the reactivity with CaO.
(2) In 1796, forty years after Smeaton, James Parker(UK) invented Roman cement, as also mentioned in
Chapter 2. This Roman cement is produced byburning clay-containing limestone (marl) in alimekiln at an estimated 1100ºC and then crushed. It

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchwould have hardened sooner and been more water
resistant than the cement used since ancient times (amixture of slaked lime and volcanic ash). It was
widely used in the United Kingdom until the early
19th century, on projects such as tunnels under theRiver Thames.
(3) Inspired by the invention of these “hydraulicmaterials” by Smeaton and Parker, from the late 18th
century on, university professors, specialist chemists
and other experts began researching how hydrauliccement could be made from clay-containing
limestone.
(4) In 1810, the Dutch Society of Sciences offered a
prize for the submission of a paper that would answer
the question, “What is the chemical cause, in virtue
whereof clay-containing limestone makes generally
more solid and durable masonry than shell lime, andwhat are the means of improving shell lime in thisrespect?”
Johann Friedrich John (1782-1847, Germany)claimed the prize in 1815 with a paper reporting thefollowing:(1) When he immersed lime from burned
clay-containing limestone in water to dissolve all
the free lime and treated the residue with nitricacid, he discovered “a very intimate combinationof part of the lime with silicic acid, alumina andiron-oxide” during burning.
(2) Burning shell-lime mixed with an appropriate
amount of clay yields the same result asclay-containing limestone.
(5) In 1818, Louis-Joseph Vicat (1786-1861, France)
announced his invention of a method for producing
artificial hydraulic lime. Until then, hydraulic mortar
had been made by either (1) mixing powdered brickor pozzolan with quicklime, a method used sinceancient Roman times, or (2) burning clay-containing
limestone (Smeaton’s invention). Vicat invented athird method: adding clay to quicklime or limestone
and burning it. Although Vicat’s paper was publishedafter John’s, mentioned in (4) above, the date it wassent for printing confirms that it was a separate
invention from John’s.
The term “hydraulic” (Fr: hydraulique) was also
first used by Vicat. He also invented the Vicat needle
used in current JIS standard setting tests fordetermining the setting time of cements, as well as amethod of testing cement erosion using a magnesium
sulfate solution.
(6) In 1824, Joseph Aspdin (UK) invented and patented
Portland cement, 30 years after Parker’s Roman
cement.
It should be noted that based on Aspdin’s patent,

there could be some doubt that he was the inventor of
cement, for the following two reasons.
(1) Prior to Aspdin, Smeaton had already burned
hydraulic lime, while Vicat and John had proventhat hydraulic lime could be produced byburning lime mixed with clay.
(2) Aspdin’s patent is missing two important points
from the current definition of Portland cement. It
does not mention (1) the ratio range between thelime and the clay or (2) burning the proportioned
raw materials until partially melted.
The burning temperature for Aspdin’s firstPortland cement is estimated to have been around
1200ºC. Although this would have caused thequicklime and the clay to react and produce small
amounts of belite, interstitial phases and othercement minerals, there would probably have also
been large amounts of quicklime in it as well. Thismeans it would have had very little difference inquality from Roman cement.
(7) In 1830, The Dutch Society of Sciences offeredanother prize for papers. The topic was to discover
the ideal properties of hydraulic cement and to
define the chemical bonding compound that causes
hardening.
Johann Nepomuk von Fuchs (1774-1856) ofGermany submitted a prize-winning paper within
only two months of the prize being announced. In
this paper, Fuchs concluded that the hydraulicproperties of hydraulic mortar were mainly due tochemical bonding between silicic acid and lime.
(8) Isaac Charles Johnson (1811-1912), manager of
the J.B. White Roman cement plant in England,
gained permission from his company to produce
his own version of the new cement developed by
Aspdin. In 1844, his independent research that (1)there is a ratio of lime and clay that produces goodquality cement, (2) raw materials should be burned
until partially melted and (3) proper mixing of raw
materials is a basic condition for producing ahomogenized product. Thus, he established thebasic principles of Portland cement manufacturing,which are still valid today.
Due to Johnson’s manufacturing condition forPortland cement of burning limestone and clay athigh temperatures of at least 1250ºC until partiallymelted, cement minerals dramatically improved inquality, from the belite + interstitial phases ofAspdin-era cement to adding alite as well 8).
In the 20 years between Aspdin’s patent andJohnson’s “new cement”, the Aspdin productHistory of Cement Manufacturing Technology

76seems to have lacked any consistent quality.
Johnson in later years requested the British
Portland Cement Association to recognize him as
the true inventor of Portland cement, but his
request was denied. Instead, the Association
acknowledged him as having improved Portland
cement.
In 1924, the British and American cement
associations jointly erected a plaquecommemorating the centenary of the invention ofPortland cement in Leeds, Aspdin’s birthplace.
The plaque inscription settled the dispute, citing
Aspdin as the inventor.
(9) In the late 19th century, various researchers began
to hypothesize that clinker is made up of calcium
silicate, calcium aluminate or other compounds.
One pioneering researcher who attempted toscientifically (chemically) verify these hypotheses
based on empirical testing was Henry Le Chatelier(1850-1936, France), known for Le Chatelier’s
principle of chemical equilibrium. Le Chatelier
focused on theory and made some significant
achievements, not only in cement chemistry, butalso in the wider cement manufacturing industry.
One of Le Chatelier’s major contributions to
cement chemistry was the introduction ofmineralogical techniques to cement chemistry,
namely, the use of polarization microscopes. In his
1882 thesis Recherches expérimentales sur laconstitution des ciments et la théorie de leur prise,
Le Chatelier confirmed the existence of four typesof compound mineral phases in clinker (fourcrystals and one glass phase) based on polarization
microscopic examination of clinker flake
specimens. He identified the most commonlyoccurring phase as 3CaO·SiO2 (C3S). He appears
to have used chemically synthesized C3S as areference for identification.
(10) Alfred Elis Törnebohm (Sweden) made thefollowing two new contributions to cement
chemistry with a paper published in 1897.
(1) Naming the clinker minerals observed under
microscope(2) Isolating these minerals using heavy liquid
separation
He confirmed “four crystals and one isotropic
phase (probably glass)” under microscope andnamed these, in order of occurrence frequency, alit,
belit, celit and felit. He created the names using A,
B, C and F with the prefix “-lit” added, from77

Greek lithos (stone). These names are still
currently used to refer to these minerals.
Törnebohm was unaware of Le Chatelier’s
paper, published ten years previously. He laterclarified which of the mineral phases recorded in
Le Chatelier’s paper corresponded with theminerals he had named. While the two made thesame observations regarding the clinker mineralphases observed under microscope, they tookdifferent views on the chemical compositions of
the different mineral phases. Neither view wascorrect from today’s perspective, but that isinevitable given the limitations of the analysis
methods of the day.
(11) Wilhelm Michaelis (1840-1911, Germany) was acontemporary of Le Chatelier and made asubstantial contribution to advances in cement
chemistry. He majored in chemistry at vocational
college and then worked as a chemist at a mineral
research facility and a cement plant. In 1872, heand his partners founded an industrial chemical
testing laboratory for testing building materials.
He became the head of the laboratory in 1877.
Michaelis made a wide range of contributions to
cement manufacturing technology, including (1)proposing the “hydraulic modulus” for cement
manufacturing, (2) discovering the setting
regulating effect of adding gypsum to clinker, (3)theorizing on the hydraulic properties of cement,and (4) making various proposals on cement
quality testing and standards.
Michaelis published the idea of the hydraulicmodulus (HM) in 1885. Hans Kuhl (1879-1969),
who succeeded him as the head of the laboratory,
proposed the silica modulus (SM) and ironmodulus (IM) in 1913. These basic indicators foradjusting cement raw material blends are widelyused to this day (see 7.1.3).
The discovery of the setting regulating effect ofadding gypsum was epoch-making, as mentioned
in 3.4, and shall be discussed in further detail in
7.5.1. Further contributions related to (4) cement
quality testing and standards are discussed in 8.2.1.
7.4.2

Chemistry of the Burning Process andClinker Minerals: Advances from the Early
20th Century
In the 20th century, the development of various analysis
instruments, such as X-ray diffractometers and electron
microscopes, made it possible to accurately observe,
measure and analyze the chemical compositions andcrystalline structures of clinker minerals. Research on theburning process and clinker minerals had reachedapproximate completion by the end of the 20th century.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March(1) Quick and Easy Determination Methods for
Quality of Clinker on Site: Determining Free Lime
Quantity 7) and Measuring Volume Weight
The invention of rotary kiln burning has made it
possible to burn several thousand tons of clinker per day
in one kiln. However, it can take at least three days to one
week to find out the results of the quality standard testingfor the cement produced in a day. It is very likely thatmaking adjustments on site after the results are known
will be too late. Accordingly, there is a need for quick
determination of the clinker quality on site that has comeout of the kiln and the cooler. Methods proposed include(1) determining the quantity of free lime and (2)measuring volume weight (weight per litter). Bothmethods are still currently used as measurements that canbe performed by workers on site.
A qualitative analysis of free lime in clinker was
proposed in 1909 by A. H. White (USA). This method
involved dissolving fine clinker powder in a solution ofphenol and nitrobenzene and observing the solution under
microscope.
This prompted various other studies on quantitative
analysis methods. In 1915, W. Emley (USA) proposed amethod of “extracting free lime in a solution of glycerin
alcohol and determining the quantity using ammonium
acetate”. In 1930, W. Lerch & R. H. Bogue (USA)improved this method and promoted it as a quick meansof gauging burning degree that could be used at cement
manufacturing sites. It was also adopted in the Japan
Cement Association testing standards (JCAS/I-01
Determination method for free calcium oxide). The JCAS
prescribes two methods: the glycerin alcohol method andthe ethylene glycol method.
Volume weight measurement is a method involving
separating out the coarse particles (e.g. sieve holes 10mm
or higher) and fine particles (e.g. sieve holes 5mm or
lower) from the clinker coming out of the clinker cooler
and then measuring the weight of the medium particles bypacking them into a container with a fixed volume. Thismethod is widely used at plant sites because of the simple,
easy measurement that makes it possible for the burningstate of the clinker to be read and recorded numerically as
a volume weight value. This method is thought to havebeen used for quite a long time, although it is not known
when it began.
Automated measuring methods for both free lime andvolume weight have been developed in recent years.
These play an important role today as indicators thatallow the burning degree to be determined quickly on site.
In terms of methods for measuring burning degree atchemist level, Dr. Yoshio Ono proposed a method ofdetermining the burning degree of clinker under optical
microscope in the 1960s. “Ono’s Method” became widelyused in many countries around the world. Ono’s Method
is discussed in (6) below.
(2) Creating Phase Equilibrium Diagrams for Clinker
Minerals 7)
From 1906 to 1915, many researchers at theGeophysical Laboratory of the Carnegie Institution of
Washington, United States, took part in researching thephase equilibrium of lime, alumina and silica minerals for
single oxide systems to binary-oxide and ternary-oxidesystems, and successively producing phase diagrams.
From that, G.A. Rankin & F.E. Wright published a phaseequilibrium diagram for a CaO-SiO2-Al2O3 ternary
system (Figure 7.5), which accounts for up to 90% ofPortland cement clinker.
Since then, a number of other researchers havepublished other clinker mineral phase diagrams for
systems containing Fe2O3 and systems containing MgO,
Na2O, K2O and other trace compounds. Reference (9)records almost all of these phase diagrams.

Fig. 7.5 Phase Equilibrium Diagram for a CaO-SiO2-Al2O3
Ternary System 7)(3) Use of X-Ray Diffractometers for Clinker Mineral
Research 10)
In 1912, Max von Laue (Germany) discovered thephenomenon of X-ray diffraction using the X-rays
discovered by Wilhelm Conrad Röntgen (Germany) in
1895. The following year, father and son Henry &Lawrence Bragg (UK) produced a basic theory for crystal
structure analysis using X-ray diffraction.
Peter Debye (Netherlands) & Paul Scherrer(Switzerland) came up with a method for fine powder
X-ray diffraction in 1916-1917, while A.W. Hull (USA)independently did the same in 1917. Although at the time

History of Cement Manufacturing Technology

78this method was expected to be useful for identifying,qualifying and quantifying substances, it was not used in
actual analysis until the 1930s onwards.
In 1938, J.D. Hanawalt, H.W. Rinn & L.K. Frevel(USA) proposed a method of sorting X-ray diffraction
data for quantifying and identifying. This was linked to
the ASTM cards and provided a robust and universal
analysis method for fine powder X-ray diffraction.
Amidst these advances in technology related to X-ray
diffraction, W. C. Hansen & R. H. Bogue (USA)published a paper on using X-ray diffraction to identify
clinker minerals in 1926. In 1927, E. A. Harrington(USA) used X-ray diffraction for crystal structure
analysis and, with the assumption that C3A has a cubic
crystalline structure, calculated its crystal lattice constant.
These studies were followed by later developments in
X-ray diffractometers and the creation of ASTM cards,
the Powder Diffraction File and other databases. X-ray
diffraction began to be used in cement chemistry as a very
useful and effective means of (1) identifying andquantifying minerals and (2) clarifying mineral crystal
structures. After that, research on the characterization ofclinker minerals expanded to greater depths and breadths.
(4) Proposal of a Method of Calculating Clinker
Mineral Composition 7)
In 1929, Bogue proposed a method of calculating theclinker mineral composition by replacing the clinker
chemical analysis value (weight %) with a simple formula(the Bogue formula). This formula assumes that “the fourmain cement compounds CaO, SiO2, Al2O3 and Fe2O3
ultimately become the four solid phases C3S, C2S, C3A
and C4AF” and ignores any trace compounds other than
the four main compounds.
The formula is still widely used today because it issimple and convenient for finding out the relationshipbetween the chemical composition and the approximate
value of each mineral. In many countries, in order tomaintain quality under the national standards, theamounts of particular clinker minerals shown by theBogue formula are used as indicators. They aresometimes used to prescribe maximum or minimum
values. JIS R 5210 Portland cement also prescribes
maximum or minimum values based on the Bogue
formula for mineral compositions in moderate-heat
cement, low-heat cement and sulfate-resistant cement (seeChapter 8).
(5) Use of EPMAs in Clinker Mineral Research 11)
An electron probe micro analyzer (EPMA) is a device
that detects and identifies constituent elements in
PLFURVFRSLFUHJLRQV DURXQGȝP3) irradiated by electron
beams and analyzes the ratio (concentration) of each79

constituent element. It can analyze solid specimens
almost non-destructively.
The device was marketed in the late 1950s and gained
a lot of attention among cement chemistry researchers. At
the 5th International Congress on the Chemistry of&HPHQWKHOGLQ7RN\RLQ VHH *RUǀ
Yamaguchi (University of Tokyo professor) and
Shigehide Takagi (Onoda Cement) presented their results
in a principal paper entitled “Portland Cement Clinker
Analysis”, in which they applied EPMA to clinker
characterization and analyzed the character of each phaseof clinker minerals 11). This paper brought some closure toresearch on the character of clinker minerals.
(6) Japanese Technology “Ono Method”:
Determining Clinker Quality by Optical
Microscopy 2) 12)
Despite the fact that the burning process is the mostimportant process in cement manufacturing, it isextremely difficult to ascertain hour-by-hour changes intemperature distribution, movement of raw materials andthe burning chemical reaction at different points within
the kiln. Cement raw materials are burned in a partiallymelted state and do not fully melt in the kiln. This meansthat the heating and cooling of the kiln during the entire
burning process is reflected in factors such as clinker
particle size distribution, clinker structure and clinker
mineral formation. The optical properties of clinker
minerals vary in complex and diverse ways.
Dr. Yoshio Ono (Onoda Cement) simplified theburning process into “heating rate”, “maximum
temperature”, “high temperature holding time” and“cooling rate”, as shown in Table 7.4. He found that these
correspond respectively to four optical properties ofclinker minerals under microscope: “alite particle
diameter”, “alite birefringence”, “belite particle diameter”
and “belite color”. This made it possible to estimate the“heat history” or burning conditions of clinker by asimple means of observing the optical properties ofclinker minerals under optical microscope. It also made it
possible to estimate the JIS 28-day mortar strength ofcement.
Table 7.4 Clinker Burning Conditions and Alite/Belite
Characteristics 2)
Burning
conditions

Opticalproperties

Heating rate

Excellent (4)Good (3)Average (2)Poor (1)

Fast

Slow

Maximum temperature
Alite birefringence

High

Low

High temperature holding time
%HOLWHSDUWLFOHVL]H ȝP

Long

Short

Cooling rate
Belite colorLong$OLWHSDUWLFOHVL]H ȝP

Clear

Pale yellow

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

Yellow

Short
Opaque yellow

The Ono method of clinker microscopy has thefollowing advantages:(1) Measuring is possible using only an optical(polarization) microscope, a portable and relatively
inexpensive tool that can be used anywhere at any
cement plant.
(2) Plant technicians can make measurements anddeterminations by learning the basics of cement
chemistry.
(3) Determining the burning state of the clinker caneven predict the strength of cement made from thatclinker.
Thanks to these advantages, the Ono method of clinker
microscopy received a great response all over the world.
The American Portland Cement Association (PCA)
named it “Ono’s Method” and invited Dr. Ono to holdcourses for cement companies all around the UnitedStates. This prompted courses in Ono’s Method in Japanand the rest of the world. In 1980, the PCA acknowledged
Dr. Ono’s achievements at its annual general meeting.
Ono’s Method is a great achievement that created direct
links between basic research and manufacturing sites.

7.5 Hydration and Hydrates: Formation andCharacterization

1) 2)

Present-day cement/concrete has the following fortes:(1) It is a high-strength, fireproof and durable
construction material.
(2) It exhibits practical strength within a few shortdays or weeks.
(3) It can also be freely molded.
(4) Its functionality can be further increased byreinforcing it with steel or other material.
Of the above fortes of cement/concrete, (2) and (3) are
due to hydration and its reaction products. Not only is thechemistry of hydration and hydrates very academicallyinteresting, it also plays a very important role in practicalapplications in the form of concrete.
However, this hydration often produces hydrate
products that are minute particles (microns or less) withpoor crystallinity, containing many different ions orelements. Until the popular use of electron microscopes
began in the mid-20th century, it was difficult tounderstand the true nature of the hydration phenomenon.
Nevertheless, early pioneers in the field kept up theirefforts, making detailed observations of the phenomena
they could see, and came close to the true nature of
hydration and hydrates. From the late 20th century
onwards, instrument analysis using electron microscopes
and X-ray diffraction was added to the findings of early
researchers to bring successive clarification to the matterof hydration and hydrates. However, hydration is acomplex reaction system, as mentioned below, and eventoday there is still much that is unknown about it.

(1) Cement constituent minerals are complex solid
solutions, as mentioned in 7.4 above.
(2) The hydration reaction is a heterogeneous reaction
series between solid and liquid, involving
numerous water-soluble compounds (such as Na2O,
K2O, SO3 and Ca(OH)2).
(3) The hydration products that cause setting andhardening are often minute particles with poor
crystallinity, containing many different ions orelements.
(4) Hydrates can exhibit many kinds of bonding states,
including covalent bonds, ionic bonds andhydrogen bonds, as well as having many bonding
points with each other or with aggregates.
This section briefly touches on important events in thehistory of cement manufacturing technology, namely, theaddition of gypsum, perhaps the greatest invention since
the invention of modern cement, the related hydration of
C3A and the hydration of C3S and C2S, which control the
final strength of the cement.
7.5.1

The Role of Gypsum in Hydration and theHydration of C3A(1) The Invention of Gypsum as a Setting Regulator 13)
Modern Portland cement has around 3% gypsum added.
This regulates the setting time of the cement to make iteasier to use in construction. When Aspdin invented
Portland cement (1824), it was simply made up of groundclinker. The cement product set very rapidly. Fromaround the mid-1800s in the United Kingdom, those
rapid-setting properties were compensated for throughspray weathering. In the United States, a method of
regulating setting by spray weathering was patented in
1870. In Japan, from the late 19th century to the 1920s,
factories had weathering areas for spray weathering, as
discussed in 3.2.3.
The idea of mixing in gypsum to achieve consistency
in cement setting was thought up by Wilhelm Michaelis(Germany) in 1870 (see 7.4.1 (11)). Michaelis noticed thedelayed setting effect of gypsum by observing
phenomena such as the following. A plant in Stettin,
Germany, received complaints from users accustomed to
rapidly-setting cement that the cement was taking longer
than usual to set. The plant manager Hugo Delbruck(1825-1900) investigated and found that the slow-setting
cement was stronger than the rapid-setting cement. On
hearing this, Michaelis determined that the reason for theslow setting of the cement was the high sulfur content in
the coke used, that is, the production of CaSO4 in theclinker. This is said to have led to the invention of adding
gypsum (CaSO4·2H2O). However, at the time it was
forbidden to add any other additives into cement, so
adding gypsum would have been done in secret. In 1883,
the German Cement Association officially endorsed the
addition of gypsum to cement, allowing the addition of up

History of Cement Manufacturing Technology

80to 2% gypsum.

after the Ettringen region in Germany where it isHowever, the addition of gypsum was unknown

produced as a naturally-occurring mineral (Figures 7.4,

outside of Germany in the 1880s. In the United States,

7.6, 7.7).
A huge amount of research followed on the mechanismof action of cement setting with gypsum and the related
C3A hydration reaction. The collected views up until theearly 1950s are summarized by R. H. Bogue (USA) incited reference (7), while research results up until 1995
are summarized by H. F. W. Taylor (UK) in citedreference (17).

Atlas successfully burned cement in a rotary kiln (1890,
see 3.3.1), but the cement produced was very
rapid-setting and hindered the wider adoption of therotary kiln. To resolve this issue, the company employedFrench technician P. I. Giron. Giron believed that theburning of gas in the rotary kilns reduced the sulfur
content in the clinker. Taking clues from French roadpaving, in which gypsum was dissolved in water whenusing cement, Giron resolved the issue by adding gypsum
to the cement. This led to the widespread adoption of

Unhydrated cement
particle

Initial hydration

Progressing hydration

Some liquidity is maintained at thisstage. The reaction between C3A
and gypsum produces long,pointed ettringite crystals.

Strength is developed as hydrates
expand. Ettringite reacts with C3A
to produce
hexagonal-plate-shapedmonosulfate hydrates. C3S or C2S
hydrate C-S-H also increases.

rotary kiln burning 14).
It seems that other companies in the United States had
been secretly adding gypsum to their cement as well. C.
Baumberger, president of San Antonio Portland Cementin Texas, mentioned in conversation that microscopeobservation and analysis of white particles found in

Fig. 7.6 Portland Cement Hydrate Formation Process 1)

cement ordered from Germany had shown them to be

2ULJLQDOSKRWRJUDSKV6ǀLFKL0XURL

gypsum and that the use of gypsum solved the issue of
rapid setting 15).
$VDQR&HPHQWHQJLQHHU)X\X]ǀ6DNDXFKLZDVWKHILUVWin Japan to use gypsum in cement at the Asano Fukagawa
plant after returning from studying in Germany in 1888.
However, even in Japan this came under criticism at thetime as “adulteration” (see 3.4).

Ettringite (initial hydration)

Monosulfate hydrates (several days of hydration)

Type I C-S-H (up to 20 hours of hydration)

Type II C-S-H (several months of hydration)

As this movement progressed, the improvements madeby adding gypsum spelled the end of weathering, which
had previously been used to prevent cement from setting
too rapidly. The discontinuation of weathering meant it
made possible to manufacture cement that set consistently
without sacrificing strength. The addition of gypsum tocement was a truly significant discovery in the history
cement manufacturing technology.
(2) Effects of Gypsum on Hydration of Cement 16)
Following Michaelis’ discovery of adding gypsum tocement in 1870, researchers immediately turned theirattention to the hydration of gypsum-added cement.
In 1892, Michaelis himself identified calcium
sulfoaluminate hydrate double salt as the hydration
product of cement and gypsum. He named the product“cement bacillus”. This discovery was the first step inclarifying the cement hydration reaction with gypsum
present. Later, this calcium sulfoaluminate hydrate
C3A·3CaSO4·32H2O became known as ettringite, named

81

Fig. 7.7 Typical Hydration Electron Micrographs 1)(3) Optimum Amount of Gypsum to Add 16)
The initial aim of adding gypsum was to regulatesetting. It was later found to have various positive andnegative effects on cement properties other than setting.
Attention was first drawn to abnormal expansion
taking place after hardening. Observing andexperimenting with various phenomena showed this to berelated to the amount of gypsum. In 1886, Germany
amended its cement standard, noting that “cement
containing more than 3% gypsum may exhibit abnormal
expansion”. The cement standard was revised to limit SO3
content (up to 2% at the time). After that, other countries
also began to set maximum limits for SO3 content. In
Japan, SO3 content was limited to no more than 2.0% in

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchthe 1898 Japanese Imperial Portland Cement Test
Methods.
In 1938, G. Mussgnug (Germany) and G. Haegermann(Germany) reported that a certain amount of gypsum will
maximize mortar strength and that increasing the amountof gypsum reduces drying shrinkage 18) 19). W. Lerch
researched this even further, reporting in 1946 that (1)there is an “optimum added amount” for gypsum that will
maximize strength and minimize expansion and shrinkage,and (2) the optimum added amount of gypsum is higher incements that are high in C3A and Alkalis 20). In 1950, H. S.
Meissner et al. proposed a “method of estimating the
optimum added amount of gypsum” by measuring theresidual gypsum in mortar 21). In 1955, Yamauchi &Kondo et al. (Tokyo Institute of Technology) reported
that adding gypsum could improve the sulfate resistanceof cement 22).
As a result of these studies, it was shown that cement
quality could be improved by slightly increasing theamount of gypsum over the maximum limit set by theexisting standards. In the United States, several revisions
were made from 1946 to increase the maximum allowableamount of SO3 in cement. In 1958, the United Kingdom
standards were revised in a similar direction. The current

7.5.2
Silicate Phase (C3S, C2S) Hydration 23)
With silicate phase hydration in Portland cement, C3S
hydrates rapidly while C2S hydrates considerably more
slowly, but both produce calcium silicate hydrates andCa(OH)2. S. Brunauer & L. E. Copeland et al. (USA)stated in 1958 that when hydrated at a normal temperature,
C3S and C2S produce 3CaO·2SiO2·3H2O(C3S2H3) similar
to natural tobermorite 24).
Later, a number of researchers began studying calcium
silicate hydrates (abbreviated as C-S-H hydrates). The
ratio between the C-S-H compounds was found to beaffected by factors such as hydration time and hydration
temperature. As CSHn-C3S2Hn (n=1-2.5) had the samestructure, these were represented as CSH (I). C2SHn had adifferent structure and was generally represented as CHS(II) to distinguish it from CSH (I). The research on thehydration of calcium silicate hydrates up to 1995 aresummarized by H. F. W. Taylor in cited reference (17)(see Figure 7.7). Table 7.5 shows a summary of theproperties of cement clinker mineral hydrates. Chapter 8
discusses the diversification of cement types madepossible by utilizing the different properties of theseminerals.
Table 7.5 Properties of Cement Clinker Mineral Hydrates
25)

JIS standard for SO3 in ordinary Portland cement is not
more than 3.5%.
(4) False Setting 16) 23)
Depending on the cement, a phenomenon sometimes
takes place in which mild stiffness occurs within 5-10
minutes of pouring. If mixing continues further, it willsoften again and then go back to normal setting. Thisphenomenon is called “false setting”. Many research
papers have been published on false setting since theearly 20th century. The conclusion is that it is caused by(1) dehydration of gypsum due to the heat of cement, or(2) cement weathering.
Occurrences of (1) dehydration of gypsum are mainly
caused by increased cement temperature during the finish
grinding process. Various measures have been adopted tocounteract this in the manufacturing process. Issues with
(2) occur after product shipping from the plant. Protecting
cement from weathering is an important factor in cement
handling, such as transportation and storage.
In any case, there is very little issue in using false
setting cement for concrete.

Properties

Alite (C3S)

Belite (C2S)

Aluminatephase (C3A)
Moderate

Ferritephase(C4AF)
Low

Early

High

Low

Late

High

High

Low

Low

Heat of hydration

High

Low

Very highModerate

Chemical resistanceModerate

High

Low

Moderate

Drying shrinkage

Moderate

Low

High

Low

Developmentof strength

7.6 Contribution of Japanese Researchers to
Cement Chemistry
The domain of cement chemistry is mostly academic in
the field of science. Consequently, unlike in other fields,such as engineering, it is difficult to evaluate the Japanesecontribution to cement chemistry in terms of economic
effect. The extent to which a researcher is cited by otherresearchers is sometimes used as an indicator to measurecontribution in the field of science. Accordingly, thisreport shows the prominence and success of Japanese
researchers using two indicators: (1) the number ofJapanese researchers cited in two highly authoritative
textbooks in the field of cement chemistry; and (2) the
number of research papers presented at international
conferences in relation to cement chemistry.

History of Cement Manufacturing Technology

82

7.6.1

Contributions of Japanese Researchers in
Cement Chemistry Textbooks
The following world-renowned textbooks on cement
chemistry are also known to the Japanese as “Bogue’sbook” and “Taylor’s book”.
(1) “The Chemistry of Portland Cement”, Robert
Herman Bogue, Reinhold Publishing, 1955
(2) “The Chemistry of Cement”, Vol. I & II, H. F. W.
Taylor, Academic Press, 1964
(3) “Cement Chemistry, Second Edition”, H. F. W.
Taylor, Thomas Telford, 1997

8QLYHUVLW\RI7RN\R DQG'U.DWVX]ǀ.R\DQDJL(Chichibu Cement) noted in the minutes as taking part in
the discussion on the principal papers. The fourth
congress was held in Washington DC in 1960. Althoughnone of the 20 principal papers were by any Japanese
researchers at this congress, Japanese researchers had
begun to make their presence known, presenting 6 of the48 supplementary papers. The decision was made at thiscongress that the next one would be in Tokyo.
The fifth congress was held over five days at the Tokyo

Below is a comparison of the number of Japanese

Bunka Kaikan (Ueno) in October 1968. Japan had grown

researchers out of the total number of researchers ofin international status in the world of cement chemistry

papers cited in “Bogue’s book” (1) and “Taylor’s book”

that it was invited to be the host country. At this congress,(3).

5 of the 20 principal papers were presented by Japanese

Total number of researchers cited ..................... 651

researchers. The Tokyo congress was held at the peak of

Of which are Japanese .......................................... 7

research on clinker minerals and cement hydrates,(Number of Japanese papers) .............................. 19

facilitated by developments such as electron microscopes(Only the first author of joint papers has been counted.
Also see note below.)

and EPMAs 26).
Following the Tokyo congress, the sixth was held in

By contrast, the following is a comparison from the

Moscow (1974), the seventh in Paris (1980), the eighth in1997 edition of “Taylor’s book”.

Rio de Janeiro (1986), the ninth in New Delhi (1992), theTotal number of researchers cited ................... 1535

tenth in Gothenburg (Sweden, 1997), the eleventh in

Of which are Japanese ...................................... 112

Durban (South Africa, 2003), the twelfth in Montreal(Number of Japanese papers) .............................. 45(2007), the thirteenth in Madrid (2011) and the fourteenthThis shows that the international presence of Japanesein Beijing (2015). The Japanese have continued to present

cement chemistry researchers grew dramatically in thepapers at every congress.

four decades from 1964 to 1997. “Taylor’s book” cited 20
papers by Dr. Iwao Maki (Nagoya Institute ofTechnology) and 14 papers by Dr. Hiroshi Uchikawa(Taiheiyo Cement). This number of citations is worldclass for any researcher.
(Note) Since Bogue’s book (1) and Taylor’s book (3)differ in citation list style, the comparison is
between the number of Japanese researchers out of
the total number of researchers for (1) andbetween the number of Japanese papers out of thetotal number of papers for (3).
7.6.2

The Growing Presence of Japanese
Researchers at the ICCC
The International Congress on the Chemistry of

Cement (ICCC) is an international conference forresearchers and engineers of cement chemistry. The first
congress was held in London in 1918. It has been held
every four to six years since the 1960s.
The second congress was held in Stockholm in 1938.

Note 1: Characterization
Seeking the answer to the question, “What is this really?”
In the case of cement chemistry, this refers to exploring andclarifying the crystalline structures, chemical compositions andphysical/chemical properties of clinker minerals and hydrates.
Note 2: Abbreviations Unique to Cement Chemistry
C: CaO; S: SiO2; A: Al2O3; F: Fe2O3; H: H2O. For example,
C3S means 3CaO·SiO2 in chemical formula. In this report, theseabbreviations will be used where appropriate.
Note 3: Solid Solution
The melting together of two solid phases with different physicalproperties to become one is called a solid solution. A solid
solution may be formed over the entire compositions or over alimited part of it only.
Note 4: Age
Age refers to the passage of time since adding water to cement.
Up to seven days is called “early strength”, while over 28 daysis called “long-term strength”.
Note 5: Transformation and Transition
Refers to the state in which a material has the same chemicalcomposition but different physical properties or moleculararrangement due to differences in temperature, pressure orformation conditions. The shift from transformation A totransformation B is called transition.

There were no Japanese presentations at the first or
second congress. The third congress was held in London
DJDLQLQWKLVWLPHZLWK'U6KǀLFKLUǀ1DJDL83

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchReferences (* in Japanese)
1) Japan Cement Association, Introduction to Cement &Concrete, 2013.*
2) Uchikawa Laboratory, Easy-to-Understand Cement
and Concrete Science, Chichibu Onoda, 1995.*
3) Supplied by Taiheiyo Cement Corporation.*
4) Yasutaka Kuroki, Meaning of moduli and coefficients
representing cement chemical composition, C&C
Cement/Concrete Encyclopedia, Japan Cement
Association, pp.67-68, 1996.*
5) Koichi Kasai, The Book of Cement a Century Ago
Michaelis 1869, Journal of Research of the Onoda
Cement Company, No.77, pp.15-18, 1969.*
6) Mitsuzo Fujii, “Development History of Portland
Cement (1)-(18)”, Cement & Concrete, No. 105-130,
1955-1957.*
7) R. H. Bogue, The Chemistry of Portland Cement,
Reinhold Publishing, 1955.
8) Hiroshi Uchikawa, “Social History of Cement
Material Technology (1), (2), Material Technology,
Vol. 12, No. 9, pp. 293-298, No.10, pp.320-324,
1994.*
9) American Ceramic Society, Phase Diagrams for
Ceramists, Part I, 1956, Part II, 1959.
10) Kozo Momoki and Hiroshi Uchikawa, X-Ray
Industrial Analysis Methods, Ohmsha, 1965.*11) G. Yamaguchi, S. Takagi, Analysis of Portland
cement clinker, Proceedings of the 5th International
Symposium on the Chemistry of Cement, pp.181-218,
1968.
12) Y. Ono, Microscopical estimation of burning
condition and quality of clinker, Proceedings of the
7th International Congress on the Chemistry of
Cement, Paris, Vol.2, pp. I/206-I/217, 1980.
13) Takashi Ueno, Supplement to the History of Cement
Technology, Onoda Cement, 1980.*
14) R. H. Bogue, Digest of literature on nature of setting

and hardening processes in Portland cement, Part.VI,
Rock Products, Sept.29 1928, pp.65-68.
15) E. Shaw, The rock products industries in Texas, Rock
Products, July 23 1927, pp.56-60.
16) Kunihiro Takemoto, Effect of Gypsum in the Settingand Hardening of Portland Cement, University ofTokyo doctoral dissertation, 1960.*
17) H. F. W. Taylor, Cement Chemistry, 2nd ed., Thomas
Telford, 1997.
18) G. Mussgnug, Einfluss einiger Kalziumsulfatsorten
auf die Eigenschaften des Zementes, Zement, Vol.27,
No.20, pp.303-307, 1938.
19) G. Haegermann, Die Beeinflussung des Schwindens
von Portlandzement durch Sulfate, Zement, Vol.28,
No.40, pp.599-602, 1939.
20) W. Lerch, The influence of gypsum on the hydrationand properties of Portland cement pastes,
Proceedings of ASTM, Vol.46, pp.1252- 1297, 1946.
21) H. S. Meissner, The optimum gypsum content of
portland cement, ASTM Bulletin, No. 169, p. 39(TP-225), 1950.
22) Renichi Kondo and Toshiyoshi Yamauchi, “Theproper modification and content of gypsum incement”, Journal of the Ceramic Association, Japan,
Vol. 63, No.705, pp.42-46, 1955.*
23) Eitaro Ushiro, New Cement and Cement Technology,
Seibundo-Shinkosha, 1971.*
24) S. Brunauer, D. L. Kantro, L. E. Copeland, The
stoichiometry of the hydration of ȕ-dicalcium silicate
and tricalcium silicate at room temperature, Journalof the American Chemical Society, Vol. 80, No. 4, pp.
761-767, 1958.
25) Japan Cement Association, Introduction to Cement &Concrete, p.20, 1994.*
26) Proceedings of the 5th International Symposium on
the Chemistry of Cement, Tokyo, 1968.

History of Cement Manufacturing Technology

84

8

Trends in Cement Standards and the History of
the Cement Types and Blended Cements

It goes without saying that standards are extremely
important in any industry, both for business transactions
and for technological improvements. In particular,
standards are of very high importance in the cement
industry for the following two reasons:(1) Cement is the most important constituent ingredientin concrete. Concrete structures are expected to havea service life of 50 to 100 years or more. The only
expectation consumers have for cement is that it
performs the core function in the concrete. Cement
standards could also be called cement manufacturers’
promise to their customers.
This also means that when cement standards are to
be revised or amended, consumers are very vigilant
about safety and confidence. Due to concerns oversafety and user confidence, it took some time for thetechnical research results on the addition of gypsum
and the use of grinding aids to be reflected in thestandards, as previously mentioned (see 3.4 and5.5.2).
(2) For manufacturers, “making JIS standard cement” isthe entire reason the company exists. This is because
the end use for around half of all cement is for public
works, and the specification documents from thepublic agencies placing orders for those works
generally require the use of JIS standard approved
cement.
There is another important point related to standards.
The cement manufacturing and distribution system inJapan comprises mass transportation from large-scale
coastal plants by large ships to terminals in consumer
areas (see 4.12.3). This highly rationalized manufacturing
and distribution system makes it possible to have asurprisingly low price for a heavy chemical product.
Incidentally, the price of cement in 2013 was around¥10,000/t = ¥10/kg1) for ordinary Portland cement. This
manufacturing and distribution system was established on
the idea of “fewer product types, mass production, bulk
distribution”. Accordingly, it is difficult to benefit fromsuch a manufacturing and distribution system except forcement for large-scale use. Therefore, there is sometimes
little hope for achieving a standardized commercial
product from a business point of view, even if it is along-awaited new technology or new material. There areeven some product types that are already establishedunder the standards, but are not actually being
manufactured or marketed because of high manufacturing
and distribution costs.
Given the business conditions such as the above85

surrounding cement standards, Chapter 8 discusses thetrends in the Japanese cement standards accompanying
changes in the market and technological advances, as well
as retracing the history of the types of cement andblended cement.
To provide an understanding of trends in standards anddiversification of cement types, Section 8.1 introduces (1)JIS regulated cement on the Japanese market, (2) special
non-JIS-regulated cement on the Japanese market, such as
found in cement company catalogs, and (3) the JISsummaries (items) related to cement testing methods.
Section 8.2 discusses the course of events that led tothe establishment of the cement standards based on theGerman example and follows the trends in cement
regulations in Japan from the establishment of the 1905
Japan Portland Cement Testing Methods through to the2010s.
Section 8.3 retraces the origins and innovations foreach of the main cement types introduced in 8.1.
8.1.1

JIS Standards Related to Cement as at2015 2)The Japan Industrial Standards (JIS) related to cement
currently (as at April 1, 2015) comprise five standards
relating to product quality and four standards relating totest methods.

(1) Product Quality Standards (five standards)* Portland Cement: JIS R 5210
1 Ordinary Portland cement; 2 High-early-strengthPortland cement; 3 Ultra-early-strength Portland
cement; 4 Moderate-heat Portland cement; 5
Low-heat Portland cement; 6 Sulfate-resistantPortland cement* Blended Cement
1 Portland blast-furnace slag cement: JIS R 5211
2 Portland pozzolan cement: JIS R 5212
3 Portland fly-ash cement: JIS R 5213
Types A, B and C of each of these; nine types in total* Ecocement: JIS R 5214
Ordinary and rapid-hardening, two types in total
For reference, the cement compositions are shown in
Figure 8.1. For details on the standards, see citedreference (3).
(2) Test Method Standards (four standards)
Standardized test methods enacted to assess theproperties of cement include physical tests to determine

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchClinker

Small amountsof additives

PortlandcementGypsumfactors such as strength and fineness, chemical analysis
and X-ray fluorescence analysis to determine chemicalcomposition, and hydration heat tests to determine theheat of hydration. These standards are used to confirm thequalities designated by the cement quality standards. The
results obtained using these test methods are recorded in a
cement test results table.
JIS R 5201 Physical Testing Methods for Cement
JIS R 5202 Methods for Chemical Analysis of Cements
JIS R 5203 Determination of the Heat of Hydration of
Cement (Solution Method)
JIS R 5204 Chemical Analysis Method of Cement by
X-ray Fluorescence

Portland cement

Ordinary
ecocement
clinkerOrdinary
ecocement

GypsumClinker

Main admixture
Smallamounts ofadditives

GypsumorLimestone

BlendedcementFig. 8.1 Composition of JIS Regulated Cement 2)

8.1.2
Special Cement 2)
Some cements are used where a quality is required that
falls outside of the scope regulated by JIS R 5210. These
are generally termed special cements. Since these cover abroad range, some typical examples are shown in Figure8.1. This report discusses “belite cement” and “white
cement”, which are relatively higher in production. The
former is discussed in 8.3.1 (4) and the latter in 8.3.1 (7).
Table 8.1 Types of Special Cement 2)
Classification
Based on Portland cement

Portland cement with modified
composition or fineness
Different composition from
Portland cement

Cement Type
Expansive cement
Binary low-heat cement
Ternary low-heat cement
Belite cement
White Portland cement
Ultrafine particle cement
Oil well/geothermal well cement
Ultra-rapid hardening cement
Alumina cement

8.1
8.2 Origin and Trends of Cement Standards
8.2.1
Origin of Cement Standards 4)
The world’s first cement standards were established inGermany in 1878. This was pioneered by Hugo Delbruck(1825-1900) and Wilhelm Michaelis (1840-1911).
Delbruck took the lead in bringing the German cement

industry together, while Michaelis produced the draft
standards.
Delbruck and Michaelis are also mentioned in 7.5.1 (1)with the discovery of adding gypsum (1870). Delbruck
was the manager of a plant in Stettin, Germany, that hadcomplaints of cement setting slowly where it had
previously set rapidly. He proved that slow-setting
cement was stronger than rapid-setting cement. This led
to the discovery by Michaelis of adding gypsum.
Although the Stettin plant under Delbruck was run down
and in financial difficulty, he used science to improve theplant’s facilities and operations and rebuilt it into a highly
profitable plant.
Having successfully rebuilt the Stettin plant, Delbruckearned reputation and credibility in the industry. He
founded the German Cement Manufacturer’s Associationin 1877 and served as its first chairman until 1899. One of
the five items in the association’s founding charter (andthe most important in hindsight) was the establishment ofstandards for procuring and testing Portland cement.
Michaelis produced and presented the draft. In 1872,
Michaelis established the Chemical Industrial Testing
Laboratory for the purpose of testing construction
materials.
The German cement industry in the 1860s had no
unified methods for cement testing. Each plant devised
their own tests to carry out. The industry was in disarray,with even the weight of one barrel of cement varying
depending on whether it was net weight, whether thebarrel was wrapped, whether German pounds were usedor whether English pounds were used. Wanting to lay afoundation for the future prosperity of the industry,
Delbruck brought order to this chaos and set to founding
an industry association.
The proposal reviewed by the Cement Manufacturers’
Association was promulgated by German (Prussian)government ordinance and was adopted for all Portland
cement supplied for government projects. This official
standard was the forerunner for the cement standards now
used all over the world. It regulated the following fiveitems and their test methods.
(1) The weight of one barrel; (2) setting time; (3)soundness; (4) fineness; (5) 28-day strength.
8.2.2

The Origin and Later Development of
Cement Standards in Japan 5) 6)
The first cement standard in Japan was the Ministry ofAgriculture and Commerce Notice No. 35 Japan Portland
Cement Testing Methods, promulgated on February 10,
1905. Details on the situation before this standard wasestablished are given in 3.6.2 and 3.6.3 and are not

History of Cement Manufacturing Technology

86repeated here. This notice by the Ministry of Agriculture
and Commerce is viewed as Japan’s first industrial
standard. Subsequent cement standard trends can begrouped into the following three broad stages.
(1) 1900s to the 1950s
Advances in cement chemistry anddevelopments in analysis methods and testing
equipment added to the depth of the standards.
Changes were also made to the standards due toindustrial controls during the Pacific War.
(2) 1960s to the 1980s
Standards were added to as cement types
became more diverse.
(3) 1990s to the present
As the cement industry became globalized,
revisions were made to maintain consistency with
ISO international standards. Other revisions weremade to ensure the cement industry fulfilled its
role as a contributing industry in a sustainable
resource-recycling society.
Ministry of Agriculture and Commerce Notice No. 35
Japan Portland Cement Testing Methods was simply astandard for government purchasing. However, thepromulgation of Japanese Engineering Standard No. 28(JES 28) in 1927 placed the cement standards at national
standard level. With the passing of the Industrial
Standardization Act in 1949, the cement standards
became Japanese Industrial Standards (JIS).
As previously mentioned, the cement JIS standards
included product quality standards to determine standardsof quality and test method standards for testing the quality.
Demand from society and advances in technology
resulted in further types of cement being produced.
Standard quality test items and standard values weremodified as cement quality improved. Test method
standards were also modified as science advanced toensure they remained universal. The main revisions are
summarized below. For details, see cited references (5)and (6).
(1) 1927 revision
Under this revision, more details were stipulated on
testing temperature, specimen regimen and methods fortesting setting and strength. The standard sand was also
FKDQJHGIURP7RN\RVDQGWR6ǀPDVDQG VHH  EHORZ 
The changes were widespread, including revised
terminology, such as “elongation resistance” changed to“tensile strength” and “pressure strength” changed to“pressure resistance”.

87(2) Major revisions of the test method for mortar
strength (1941)
There were major revisions in 1941, includingchanging the test method for mortar strength, the mostimportant characteristic of cement quality, from theexisting hard method to the soft method and changing
from measuring tensile strength to measuring bending
strength. Accordingly, it is difficult to compare previous
test data with modern values accurately.
(3) Standards under wartime industrial control
During the Second World War, it was not possible tomanufacture high quality cements, such as
high-early-strength cement and moderate-heat cement,
due to poor coal quality and shortages of manufacturing
materials. However, there was increased production of
blast-furnace cement and pozzolan cement, as theserequired less coal and materials. For a time, these cements
accounted for a third of all cement produced. Following
an appeal to rationalize the use of cement, standards werecreated for lower-strength, non-structural cements, suchas masonry cement and non-construction cement. These
cements then emerged on the market. The standard for
non-construction cement (enacted in 1942) stipulated
manufacturing by mixing and grinding “Portland cementclinker, quenched blast-furnace slag, cement kiln dust,
pozzolanic materials, gypsum, lime and other materials
having equivalent properties”. Production ceased after the
war and the standard was abolished in 1956.
(4) Standard sandIn cement strength testing, cement strength varies
according to the type of sand used. The standard sandused for mortar testing in Japan was Tokyo sand from thelate 19th century to the late 1920s. In 1927, the standard
VDQGZDVFKDQJHGWRVDQGIURP6ǀPDLQ)XNXVKLPD7KLVwas changed again in 1941 to sand from Kumipo in
Korea. Since this was no longer accessible after the war,
the standard sand changed again in 1947 to sand from
Toyoura in Yamaguchi. In April 1997, the standard sandwas changed once more to Australian sand, in order toconform to the international standard (ISO 679). Standard
sand conformance testing and quality checking is usually
carried out by the Japan Cement Association.
(5) Minor additives
In 1979, the stipulation was added that ordinary
Portland cement could contain “up to 5% minor additives”
to economize resources. There were four approved
additives: blast-furnace slag, siliceous materials, fly ash
and limestone. Later, a JIS amendment in 2009 allowed
the addition of minor additives to high-early-strength
cement and ultra-early-strength cement.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March(6) Regulating alkali content in cement 7) 8)
In 1986, new regulations were enacted for low-alkaline
Portland cement in order to control alkali-aggregate
reaction. Depending on humidity level and otherconditions, bases (Na+, K+) contained in cement cansometimes react with certain types of minerals in theaggregate, causing volume expansion. This phenomenon,
known as “alkali-aggregate reaction”, can cause local
volume expansion in concrete, causing cracks andweakening the concrete. In extreme cases, the concrete
can even break apart. In order to avoid this risk,
low-alkaline Portland cement was stipulated for whenalkali-aggregate reactive aggregates must be used.
While the alkali-aggregate reaction has long been
known about in the West, little care was taken in Japan,
the belief being that “aggregates in Japan do not cause
alkali-aggregate reaction.” However, since 1983, concrete
structures have been found to have been weakening due
to the reaction, particularly in the Kansai area. Thisbrought the issue to attention that alkali-aggregate
reaction also happens in Japan, with greater attention paid
to the alkali content of cement.
As a result, when the JIS R 5210 Portland cement
standard was amended in 1986, a section was added on
low-alkaline cement, setting the upper value at 0.6% for
the total alkali content, expressed as the total Na2O andK2O converted to Na2O.
The stipulated total alkali value of “0.6% or less” inlow-alkaline cement was determined as follows. The
problem of alkali-aggregate reaction had long been
known in the United States. American studies in the
1940s confirmed that “almost all damage to concrete due
to alkali-aggregate reaction can be prevented if the alkali
content of cement is 0.6% or less”. The American
standard set the alkali value at 0.6% for low-alkaline
cement. Many countries in Europe also set the alkali
value at 0.6% for low-alkaline cement. With Japanese
research results also reporting that 0.6% was safe, Japan
also set the value at 0.6%.
However, the cement manufacturing and distribution
system in Japan involves large-scale transportation of
cement from large coastal plants to terminals in consumer
areas. This made it very difficult to supply both ordinary
Portland cement with no alkali restrictions as well as
low-alkaline cement.
Accordingly, the standards were revised in 1992 toestablish a new standard “full alkali” value for all
Portland cement. The upper alkali content value of fullalkaline cement was set at 0.75% or less. This meantconsumers had a guarantee that all JIS approved Portland
cement had an alkali content of 0.75% or less, meaningthat low-alkaline cement would only be ordered whenabsolutely necessary. This effectively resulted in almost
no further demand for low-alkaline cement.
Of the cement standards around the world, only a verysmall minority (only Japan as at 2005) stipulate the alkali
content for all Portland cement. The alkali-aggregate
reaction is affected by the total alkali content of theconcrete rather than the alkali content of the cement. The
other materials used to make up the concrete (gravel, sand,water, additives, agents, etc.) should also have an equalpart to play. However, in Japan, this is achieved throughmaterial regulation (see Note 1), only by regulating
cement, as cement manufacturers are generally larger atenterprise scale than other concrete-related material
suppliers 8). This idea was carried over into the later
regulation of chloride ions (see following section).
(7) Chlorine 8)
In 1992, new standards were enacted to regulate theamount of chlorine ions in order to improve the durabilityof reinforced concrete.
Following on from the issue in the 1980s with concrete
breaking down due to alkali-aggregate reaction, as
mentioned previously, the issue of salt damage toconcrete was aired on NHK Television in 1983. In 1984,
a television program was produced called Concrete Crisis(NHK), raising doubts about the durability of concrete.
The demand for concrete had grown dramatically withthe rapid economic growth from the 1960s onwards. This
led to shortages of aggregates, particularly fine aggregates(sand). In areas around the Seto Inland Sea, sand takenfrom the sea floor was used in concrete without being
washed properly. As a result, the reinforcing steel in theconcrete corroded, causing issues with the durability of
the concrete.
Given the situation, investigation began on regulating
the maximum amount of chloride ions in concrete toprevent the reinforcing steel from rusting. In the West, themaximum allowable amount of chloride ions was
0.6kg/m3 for regular concrete and half that at 0.3kg/m3 forpre-stressed concrete of particular importance. In Japan,
the amount was set at 0.3kg/m3 for regular concrete as
well. This maximum allowable amount multiplied by theratio of constituent materials in the concrete meant
cement could contain an upper limit of 0.02% chloride.
This was stipulated in JIS R 5210 in 1992. This was avery strict figure, one-fifth of the 0.1% upper limit givenin the EN standards.
Later, as the cement industry sought to contribute to asustainable resource-recycling society, there was somemovement towards easing up on the chloride ion limit to

History of Cement Manufacturing Technology

88make it easier to utilize industrial waste. Afterconsidering the chloride content of poured concrete inreal conditions, among other factors, the allowableamount of chloride ion in cement was eased to 0.035% in
2003.
Generally, chloride penetrating concrete from externalsources, such as seawater or snow melting agents, after
the concrete structure is built has a greater impact than thechloride ions contained in the concrete.

8.3 Diversification of Concrete Types: Cement
Innovations for which there are JIS Quality
Standards
With cement types diversifying, it goes without sayingthat “cement with desired functions and qualities could be
produced consistently” as (1) cement chemistry theories
advanced and (2) cement manufacturing facilities
developed. Most new product developments from the
1960s onwards were developed based on cement
chemistry theories.
Below is a discussion of the development of Portland
cement and blended cement for which there are JIS
quality standards. Ecocement is discussed in Chapter 9“Evolving to become a Contributing Industry for the
Sustainable Resource-Recycling Society”.
8.3.1

Development of Cement Regulated by JIS
PortlandCement
Cement regulated by JIS R 5210 Portland Cement
includes (1) ordinary Portland cement, (2)high-early-strength Portland cement, (3)ultra-early-strength Portland cement, (4) moderate-heatPortland cement, (5) low-heat Portland cement and (6)sulfate-resistant Portland cement, as well as theirrespective low alkali versions. Since this whole reportcovers the history of cement manufacturing technology,
the history of ordinary Portland cement is omitted here.
This section covers the development of the cement types
from (2) high-early-strength Portland cement onwards.
More detail is given to low-heat Portland cement inparticular, as it has grown in use since the 1990s as
cement for high-performance concrete. Although white
cement is not stipulated by that name in the JIS, its
history is also included in this section because it has been
manufactured and sold in Japan for almost a century andconforms to the JIS standard for Portland cement.
(1) High-early-strength Portland cement 9)
This cement exhibits the three-day strength of ordinary
Portland cement in one day. After modern Portland
cement was invented in the late 19th century, it spread inuse, with various new applications found for it. Design89

and construction considerations led to demand forPortland cement with higher initial strength. Spindel ofthe Austrian State Railways devoted himself to thisresearch. He refined the manufacturing process, and byheavily burning highly calcareous raw material and by
finely grinding the clinker obtained, succeeded in
producing high-early-strength Portland cement in 1913.
Later, this cement began to be manufactured indifferent countries around the world. The first instance inJapan was a trial manufacture of “high quality cement” inE\2VDND<RJ\ǀ QRZ6XPLWRPR2VDND&HPHQW 
In 1929, Asano Cement started marketing it under thename of “Asano Velo-Cement”. After that, othercompanies began producing and marketing it under
different names, such as “fine Portland cement” and “highquality Portland cement”. High-early-strength Portland
cement was standardized in 1938 (by a Ministry ofCommerce and Industry Notice).
(2) Ultra-early-strength Portland cement
This cement exhibits the seven-day strength of ordinary
Portland cement in one day. It was developed in Japan
using cement chemistry expertise for use on emergency
construction projects. Production began in 1969 and the
product was standardized under the JIS in 1973. However,technology was later developed that made it possible toproduce “ultra-early-strength concrete” by using concrete
additives rather than ultra-early-strength cement. As aresult, ultra-early-strength cement is no longer produced,
although there is a standard for it.
(3) Moderate-heat Portland cement 10)
This cement has more belite (C2S) and less alite (C3S)
and aluminate phase (C3A) than ordinary Portland cement,
resulting in a lower heat of hydration. This cement offers
superior long-term strength and is used in dams and othermass concrete applications.
It was discovered around 1930 in the United States that
“increasing the amount of belite in cement and reducing
the amount of alite, interstitial phases, particularly C3A
solid solution, reduces the heat of hydration”. The firstuse of “low-heat cement” based on this finding is thought
to have been the Pine Canyon Dam project (California,
USA) in 1932. It was also used for the well-known
Boulder Dam (Hoover Dam) in 1933.
In Japan, the cement was first manufactured andmarketed in 1934 by Asano Cement as “Asano Mascon
Cement”. Its first use in a project is thought to have been
the building of the dam for the Tsukabaru Power Stationin Miyazaki in 1934. The cement was standardized under

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchthe JIS in 1953.
Until the 1970s, the only “low-heat cement” in Japan
was the JIS “moderate-heat” cement. From the 1980s,“low-heat cement” and “belite cement” emerged, making
it possible to choose from “moderate-heat”, “low-heat” or“belite” cement accordingly when a concrete design
required lower hydration heat. “Moderate-heat cement”
was produced to order for large-scale dams or other suchprojects.

Portland cement and other belite cement began to be usedin the production of high-strength concrete.
The first product on the market was commercialized in
1992 by Chichibu Cement as “High Flow Cement”.
“Low-heat Portland cement” was standardized under the
JIS in 1997.
Although there are prior examples of belite cement
overseas, the present-day high-performance product is the
cement developed in Japan. To provide an outline of thisdevelopment based on cement chemistry, the(4) Low-heat Portland cement and belite cement

11)

12)

JIS “low-heat Portland cement” has a lower heat ofhydration than moderate-heat Portland cement. In termsof its composition, it is stipulated as containing 40% ormore belite (C2S) and 6% or less aluminate phase (C3A).
It is a high-performance cement, exhibiting the functions(1) to (7) listed below. Accordingly, the product issometimes designed with a clinker composition ratio or
specific surface area that deviates from the JIS standards,
depending on usage conditions and purpose. This non-JIS
cement is called “belite cement” and is treated as “special
cement” (see Table 8.1). In other words, low-heatPortland cement is a type of belite cement.
The history of belite cement can be traced back to the“low-heat cement” stipulated in the American ASTM
standards as “Type IV”. Following the two oil crises of
the 1970s, the spotlight fell on belite from anenergy-saving perspective, as it has a lower burningtemperature and requires less heat for decarbonizing thandoes alite. Germany and the United States led thedevelopment research on high belite cement. While thiswas happening in the West, Japan was researching highbelite cement with the focus on “low heat”. Thus,
research and development of high belite cement began inJapan through improvements to the clinker itself, basedon demand for cement manufacturers to produce low-heat
cement for use in large-scale concrete applications such
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characteristic features of low-heat Portland cement aresummarized below.
1 Effective in preventing temperature cracking
Since the hydration heat is low, there is little rise in
the adiabatic temperature of the concrete. This and thelow heat release rate effectively prevent cracking fromthermal stress.
2 Superior long-term strength development
Since it is high in belite (C2S), which offers superior
long-term strength development, it continues toincrease in strength for a long period of time.
3 Optimum for high-strength and high-fluidity concrete
Low-heat cement has fewer interstitial phases, which
tend to absorb admixtures, and therefore the amount ofboth unit water content and high-performance AE (seeNote 4) to add can be reduced. Consequently, it issuitable for making high-strength, high-fluidity
concrete (see Notes 2 and 3). The development of
cement that is not only low-heat but also capable ofhigh-strength and high-fluidity, coupled withimprovements in high-performance AE water reducing
agents, led to the development of high-strength andhigh-fluidity concrete.
4 Superior chemical resistance
Since it contains little aluminate phase (C3A), which
is low in chemical resistance, this cement has higher
chemical resistance against substances such as sulfates.
5 Low autogenous shrinkage (see Note 5)

At the same time, urban concrete structures were being

Since it contains little aluminate phase (C3A), which

made taller, requiring higher strength concrete. However,is a primary cause of early volumetric change, it is lesshigh-strength concrete requires increased cement perprone to autogenous shrinkage than other types of

cubic meter. Therefore, using ordinary Portland cement
would create a lot of hydration heat, causing issues suchas temperature cracking and decrease of long-term

cement.
6 Effective in preventing neutralization
Since it is a clinker-type cement rather than astrength. To overcome this, research began on the use ofblended low-heat cement made using admixtures of

low-heat high belite cement in high-strength concrete.

blast-furnace slag powder or fly ash, the alkalinity of

The results showed that high performance AE water

the concrete is retained for longer, thus sustaining the

reducing agents worked effectively in high belite cement,

neutralization-preventing effect for longer.

with superior fluidity and long-term strength. Low-heat

History of Cement Manufacturing Technology

90

(5) Sulfate-resistant Portland cement 13)
This cement is highly resistant to sulfates. It is used in

2 The iron component is in the ferrous (Fe++) phase in
the atmosphere of the burning zone. The clinker

sulfate-rich environments, such as in the sea, in themust be rapidly cooled in order to prevent the ironground near hot springs, sewers, industrial drainage and atcomponent from entering the ferric (Fe+++) phase andchemical plants.

producing color in the cooling process.

When hardened Portland cement is exposed to sulfates

3 Ball mills are used for grinding both the raw

in soil, groundwater, running water or seawater, it erodes.

materials and the clinker. To prevent the ironStudies on cement that resists this erosion effect began incontamination, ceramic grinding media are used

Europe and North America in the late 19th century. Thisrather than iron grinding media.
The world’s first white cement was manufactured at aplant in Heidelberg, Germany, in the 1880s. This wasaround 60 years after Aspdin’s invention of Portland
cement. The first white cement in Japan was produced at
Onoda Cement’s Onoda plant in Yamaguchi in 1916. The
demand for it steadily grew after that, except during the
war and for a time after it. White cement began to be
produced by a couple of companies in Japan. By the late1970s, as much as 500,000 tons were being produced per
year. However, Japan later lost its competitive edge forexports to the Middle East and East Asia, which had
accounted for more than 50% of production. As at 2015,
white cement was only being produced by Sanyo White
Cement (Itosaki, Hiroshima), a subsidiary of Taiheiyo
Cement. For details on the chemical and physicalproperties of white cement, see cited reference (14).

was later backed by theoretical evidence from cement
chemistry, leading to the creation of sulfate-resistantPortland cement.
C3A (3CaO·Al2O3) in Portland cement reacts withsulfate to produce ettringite (see 7.5.1 (2) and Figure 7.4).
The ettringite produces very high crystal growth pressure,which breaks down the structure of the concrete andmortar, thus weakening the structure. Consequently,
sulfate-resistant Portland cement is made using far lessC3A (4% or less under the JIS), which increases thechemical resistance of the cement against sulfate. The JIS
standard was announced in 1978.
(6) Low-alkaline Portland cement 7)
This cement has a total alkali content of 0.60% or less.
This is stipulated as being allowed for use when thematerial used in the concrete “cannot be deemed harmless”
in regards to alkali-aggregate reaction. See 8.2.2 (6) forthe course of events leading to the enactment of thisstandard.
(7) White (Portland) cement 14)“White cement” is literally pure white cement.
However, since it differs very little from ordinary
Portland cement in terms of its chemical and physicalproperties, it can be represented as “JIS ordinary Portland

8.3.2

Development of Cement Regulated by JIS
BlendedCement 15)
There are three types of blended cement regulated by
the JIS: blast-furnace slag cement, pozzolan cement andfly-ash cement. These all share the common properties ofhigh long-term strength, high chemical resistance and low
hydration heat. These effects are due to the latent
hydraulicity of blast-furnace slag cement and the
pozzolanic reactivity of pozzolan cement and fly-ash
cement. Before discussing these cements in detail, thefollowing is a simple explanation of latent hydraulicity
and pozzolanic reactivity, which are important tounderstanding the functions of blended cement.

cement”. It is widely used, mainly for interior andexterior finishes on buildings, artificial marble, coloredcement and concrete landscape products.
In terms of manufacturing, it differs from ordinary
Portland cement in the following three important ways.
1 For the raw materials, limestone and clay are chosenthat are very low in iron oxide, manganese oxide orother color-producing components. These
components must be kept to a minimum in theclinker.

91<Latent Hydraulicity> 16)
Granulated blast-furnace slag is a white or brown
pumiceous particulate substance. It is formed by rapidly
water-cooling of molten slag from a steelworks blast
furnace.
Granulated blast-furnace slag does not harden bysimply being mixed with water; however, a hardening
hydration does begin due to the presence of alkali andother basic substances. This is called “latent hydraulicity”.
The bases play a role as “stimulating agents”.
Granulated blast-furnace slag latent hydraulicity
becomes evident as the stimulant bases cause the pH level

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchof the solution to rise above 12. Granulated blast-furnace
slag that is stimulated by stimulants elutes Si, Ca, Mg, Al
and other ions, which produce hydrates. The eluted
substances maintain the pH level of the solution, whileions continue to dissolve and hydrates continue to form.
The structure hardens as the blast-furnace slag hydration
progresses.
Portland cement clinker functions as a stimulating
agent because the hydration reaction produces Ca(OH)2and the pH level of the solution rises above 12. As aresult, blast-furnace slag mixed with Portland cement isused as blast-furnace slag cement.

<Pozzolanic Reactivity> 17)
Pozzolan refers to a fine powder admixture of natural
or artificial siliceous materials, primarily made up ofsilica (SiO2) or silica and alumina (Al2O3). While it does
not harden of its own accord when mixed with water, it
reacts with calcium hydroxide (Ca(OH)2) in the presenceof water at normal temperature and hardens into an
insoluble substance. This phenomenon is called the“pozzolanic reactivity”. It is similar to but distinct fromthe above-mentioned latent hydraulicity. It is similar inthat the alkalinity causes the elution of SiO2, which reacts
with CaO to harden. However, it differs in that latent
hydraulic materials harden due to their own CaO after thereaction has commenced, whereas pozzolan contains no
CaO and requires the necessary CaO to be provided
externally for producing hydrates and hardening.
High-early-strength Portland cement and ordinary
Portland cement produce high amounts of calcium
hydroxide (Ca(OH)2) through hydration. This Ca(OH)2serves little purpose in strength development. It is also
more soluble than calcium silicate or calcium aluminate
hydrates and is more likely to dissolve on prolonged
contact with water. Accordingly, adding pozzolan
containing soluble silica or alumina to Portland cement
stabilizes it by mixing with the Ca(OH)2 produced byhydration to form calcium silicate and calcium aluminate
hydrates. This ultimately contributes to improved
impermeability of the hardened concrete, greaterchemical resistance, lower heat of hydration andimproved long-term strength.
Pozzolan can be categorized as natural or artificial.
Artificial pozzolan includes fly ash, silica fume and ricehusk ash. Natural pozzolan can be categorized as
substances mainly made up of silica and alumina, such as
volcanic glass and clay, and substances mainly made up
of silica, such as opals and diatomaceous earth.

(1) Blast-furnace slag cement 18)
This cement is made up of blast-furnace slag powder
from steelworks mixed with Portland cement. It has highlong-term strength, low heat of hydration and goodseawater and chemical resistance. It is mainly used in
major civil works such as dams and harbors.
Blast furnace slag is produced by rapidly cooling slagwith water and then grinding it to make a glassy granularslag (water-granulated slag). Emil Langen, director of aniron and steelworks in Germany, studied the reaction
between this water-granulated slag and lime. He
discovered the latent hydraulicity of water-granulated slagin 1862.
Around 1870, Wilhelm Michaelis (see 7.4.1 (11))
published the finding that “mixing Portland cement with apozzolan, such as volcanic ash, or water-granulated
blast-furnace slag improves the properties of the Portland
cement”. In other words, he made the following two
discoveries.
1 The known pozzolanic reactivity effect and latent
hydraulic effect caused by quicklime or slaked lime
worked exactly the same way with Ca(OH)2 eluted
from Portland cement.
2 After the concrete hardens, the residual Ca(OH)2 in theconcrete is drawn out by the pozzolan andblast-furnace slag, thus preventing concrete fromdeterioration by carbonation with CO2 in the air.
Following this discovery by Michaelis, Godhard
Prussing (Germany) manufactured the first blast-furnace
slag cement in 1882 at the Vorwole plant in Germany bymixing Portland cement with 30% water-granulated
blast-furnace slag. There appears to have been someintense discussion at the time between the inventor and
the German cement association regarding the purity of thecement.
In 1901, blast-furnace slag cement containing 30% orless slag was named “Eisen Portlandzemente (ironPortland cement)” in Germany. The product wasstandardized in 1909. In 1907, Prussing’s son Paulproduced blast-furnace slag cement containing 60-70%
blast-furnace slag (Hochofenzement). This wasstandardized in 1917.
In Japan, Yawata Steel Works began researching this in1910 as an effective way to utilize blast-furnace slag.
Industrial production commenced in 1913 and an
integrated production system from clinker was completed
by 1918.

History of Cement Manufacturing Technology

92

A standard was also created in 1926. Under the JIS
modified in 1960, there are three types of blast-furnace
slag cement, depending on the amount of slag contained:
A (30% or less), B (more than 30%, up to 60%) and C(more than 60%, up to 70%).
(2) Pozzolan cement 9)
This cement is blended with natural silica admixtures(stipulated under the JIS as material containing 60% ormore SiO2). While pozzolanic reactivity improves
concrete’s permeability, durability and chemical
resistance, proper care needs to be taken as the concrete
has poor early strength and is susceptible to drying
shrinkage.
While this type of cement can be traced back to the“lime mortar from slaked lime mixed with pozzolan” usedfrom Greek and Roman times and throughout the Middle
Ages, Michaelis was the first to come up with the idea ofusing Portland cement instead of slaked lime, as
mentioned in the previous section on blast-furnace slag
cement. By the end of the 19th century, “Portland
pozzolan cement”, high in good-quality pozzolan, wasbeing sold in large volumes in Germany, Italy and othercountries.
In Japan, Onoda Cement supplied a blended cement
made by mixing three parts cement to one part volcanic
ash in 1899 for use on a dock at the Sasebo naval port.
The purpose was to improve chemical resistance (sulfate
resistance) of the cement.
In the 1910s, a type of blended cement was producedby mixing calcined granite powder. Later, from around
1935, this began to be produced by a couple of cementcompanies under brand names such as “silicate cement”.
In 1940, a standard was created for this “silica blended
cement”. The name was changed to “pozzolan cement”
through a revision of the standard in 1947. There are three
types of this cement regulated under the current JIS,
depending on the amount of admixture contained: A (10%or less), B (more than 10%, up to 20%) and C (more than
20%, up to 30%).
(3) Fly-ash cement 9)
This cement is blended with high-quality fly ash (finecoal ash) produced from the combustion of coal, mainly
at thermal power stations. High-quality fly ash is a type of
artificial pozzolan. Due to the pozzolanic reactivity, it
improves the properties of the cement, such as greater
long-term strength, lower susceptibility to drying
shrinkage and permeability and better chemical resistance.
Since the particles are spherical, it also improves theworkability of the concrete. It is mainly used in major
civil works such as dams and harbors.
Research on the use of fly ash as an artificial pozzolan

93

admixture in concrete began in the United States around1914. The research became more active around 1937,
with the first large-scale use starting around 1940 for dam
concrete.
Research in Japan began around 1950. Production ofPortland cement blended with fly ash began in 1956
under the name “pozzolan cement”. Under the JIS
amendment in 1960, it was regulated as “fly-ash cement”.
Like other blended cements, three types are regulated,depending on the amount of fly ash contained: A, B andC.

8.4 A Change in Lead Roles: The Lead Role inHigh-Performance Concrete Changes from
Cement to Chemical Additives11) 19)There are two ways cement itself can be made toachieve a specific function or performance: (1)improvements in the clinker minerals, and (2) adjustments
to the cement particle size or shape. Thus far, Chapter 8
has discussed the development of different types of
cements with various functions by “improvements in theclinker minerals”. However, it can be seen that improving
the function and performance of cement this way hasreached a limit. Very little clinker-based cement function
development is now being carried out anywhere in theworld.
In 1995, Dr. Hiroshi Uchikawa (then a consultant for
Chichibu Onoda Cement and a guest professor at
Nagaoka University of Technology) published a paper in
Cement and Concrete entitled “A Change in Lead Roles”
19). The paper had a major impact on those in the cement
and concrete industry, with the argument that “the leadrole in concrete is no longer cement, but chemical
additives”.
The use of concrete admixtures, particularly chemical
additives, will play an important role in the future as ameans of improving concrete and giving it new functions.
The main methods used in the development of concretewith new functions will be using adequate admixtures,
improving the performance of additives and adjusting thesize and shape of cement particles.
The knowledge thus far gained in cement
manufacturing technology and cement chemistry will playa significant role in laying the foundation for new
technology developments that will see the cement
industry achieve its new mission for the 21st century, thatof contributing to a sustainable resource-recycling society.
This will be discussed in Chapter 9.
(Note) Concrete admixtures fall outside of the scope of“cement manufacturing technology” covered inthis report, but are touched on briefly in 1.1 andNational Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

2.4 above. For more details on concrete
admixtures, see cited reference (20).

Note 1: “Material Regulation” and “Performance Regulation”
Standards can determine “material regulation”, which stipulates
different materials, and “performance regulation”, which allows
free selection of materials to maintain performance or qualities.
The current JIS cement standards are essentially material
regulations. The stipulation on the alkali content of cement(0.75%) is effectively unrelated to the stipulations for othermaterials that make up concrete (water, aggregate, admixtures,
agents, etc.). By contrast, if “performance regulation” was used,
the standard could stipulate, for instance, “to prevent alkali
aggregate reaction, the total concrete alkali content converted to
Na2O should be no higher than 3kg/m3”.
Making standards regulate performance allows users broader
options for working techniques and materials used. It also
allows suppliers to provide materials suited to the market(demand). This ultimately results in the conserving of resourcesand energy. Accordingly, there is a global trend of standards
moving towards performance regulation.
Note 2: High-Strength Concrete 2)
The compressive strength of regular concrete, JIS ready-mixed
concrete for example, is up to a “nominal strength of 45”, or
45N/mm2. Anything that is stronger than this is called
high-strength concrete. Using high-strength concrete allows forsmaller cross sections of reinforced concrete, resulting in aweight reduction. For this reason, high-strength concrete is
widely used in bridges, tanks, high-rise buildings and precast
products.
Note 3: High Fluidity Concrete 2)
Concrete that has greater fluidity to improve its workability iscalled high fluidity concrete. High fluidity concrete not onlyoffers greater fluidity, but also superior material separation
resistance. These result in greater filling of formwork, superior
strength and durability after hardening.
High fluidity concrete allows greater confidence in concrete
quality, reduces labor on site, improves the working
environment by reducing the noise of pouring and compacting,and also allows greater rationalization of the construction
system.
Note 4: High Performance AE Water Reducing Agents 10)
Also called superplasticizers, these are additives (surfactants)that significantly increase the fluidity of concrete. Using theseagents offers the same workability as regular concrete, but
reduces the unit water content, resulting in high-strength
concrete.
Note 5: Two Types of Concrete Shrinkage:<Drying Shrinkage>
This phenomenon refers to the shrinking of concrete as it dries
due to the evaporation of water added during the working of
concrete that was not needed for hydration.
<Autogenous Shrinkage>
This phenomenon refers to the reduced volume (shrinkage) of
hydrates compared to the original volume (cement + water)
following the hydration reaction of cement. Normally, theamount of autogenous shrinkage is around 1/10 of the amountof drying shrinkage. Autogenous shrinkage can be a problem inhigh-strength concrete made using water reducing agents.

References (all in Japanese)
1) Japan Cement Association, Cement Handbook, 2014.
2) Japan Cement Association, Introduction to Cement &Concrete, 2013.
3) Japan Cement Association, A Guide toUnderstanding Cement Standards: JIS Instruction“Cement Quality Standards”, Japanese Standards
Association, 2010.
4) Mitsuzo Fujii, “Development History of Portland
Cement (1)-(18)”, Cement & Concrete, No. 105-130,
1955-1957.
5) Seizaburo Hirano, “Transition of Cement Standards
in Japan”, Cement & Concrete, No.253, pp.41-47,
1968.
6) Kinjiro Murahashi, “Development of Japan Industrial
Standard for Cement”, Cement & Concrete, No.500,
pp.236-245, 1988.
7) Hideaki Okamoto, “Low-Alkaline Portland Cement”,
C3 (Cement and Concrete Chemistry) Clipboard:
Cement Industry, Japan Cement Association, pp.4-5,
2008.
8) Shunsuke Hanehara, “Progress in Cement
Technology from 1988 to 2005”, Cement & Concrete,
No.700, pp.1-11, 2005.
9) Hitoaki Mori, “The History of Cement”, Concrete
Journal, Vol.16, No.5, pp. 78-85, 1978.
10) Uchikawa Laboratory, Easy-to-Understand Cement
and Concrete Science, Chichibu Onoda, 1995.
11) Hiroshi Hirao, “Development and Contribution of
Cement Chemistry”, Journal of Research of the
Taiheiyo Cement Corporation, No.150, pp.5-28,
2006.
12) Toyoharu Nawa, “Current Status of Belite Rich
Cement”, Concrete Journal, Vol.34, No.12, pp.16-25,
1996.
13) Yuichi Suzukawa, “Sulfate Resistance”, Cement
Chemistry Theories for Concrete Engineers, Japan
Cement Association, pp.21- 24, 1985.
14) Kouki Ichitsubo, Takao Tanosaki, Hiroichi Tomotake
and Keiichi Miura, “The History of White Cement
and Its Current Technology Trend”, Journal of
Research of the Taiheiyo Cement Corporation,
No.154, pp.3-20, 2008.
15) Eitaro Ushiro, New Cement and Cement Technology,
Seibundo-Shinkosha, 1971.
16) Yasuhiro Dan, “Latent Hydraulicity”, C3 (Cement
and Concrete Chemistry) Clipboard: Cement
Chemistry, Japan Cement Association, pp.115-116,
2008.
17) Masaki Kawamura, “Pozzolan”, C3 (Cement andConcrete Chemistry) Clipboard: Cement Chemistry,
Japan Cement Association, pp.107-108, 2008.
18) Nippon Slag Association, 100-Year History ofPortland Blast-Furnace Slag Cement, 2010.
19) Hiroshi Uchikawa, “Brief Thoughts: The Lead’s
Change”, Cement & Concrete, No.585, p.25, 1995.
20) Asakura Publishing, Concrete Engineering Handbook,
I. Materials, 4. Admixtures, pp. 113-185, 2009.

History of Cement Manufacturing Technology

94

9

Evolving to a Contributing Industry for the
Sustainable Resource­Recycling Society

The Japanese cement industry has been using large
volumes of industrial waste and byproducts (see Note 1)
as alternative fuel and raw materials (AFR) since the1970s. The industry initially used industrial waste as ameans of reducing costs. But, as it later expanded fromindustrial waste to include municipal waste and othergeneral waste, the cement industry took on a new andhighly valued role of contributing to society with growing
awareness of global environmental issues and landfill
sites in increasingly short supply.
Chapter 9 discusses the 21st century development of thecement industry from a “key industry providing
construction materials” to a “core industry supporting asustainable resource-recycling society”, based on
developments in cement manufacturing technology andexpertise in cement chemistry built up throughout the 20th
century 1).
Section 9.1 outlines the kinds of waste materials
recycled by the cement industry and why this is possible.
Section 9.2 discusses the main new technologies that havebeen developed to allow greater varieties of waste to berecycled by cement plants in greater volumes. Section 9.3
discusses the contributions to post-earthquake waste
disposal PDGHE\WKH7DLKHL\R&HPHQWƿIXQDWRSODQW(which was itself badly damaged in the earthquake and
WVXQDPL DQGRWKHUFHPHQWSODQWVLQWKH7ǀKRNX.DQWǀarea following the Great East Japan Earthquake in 2011.

9.1 The Resource Recycling System Centeredaround Cement Plants2) 3)

In 2012, the Japanese cement industry recycled 28.5
million tons of waste and byproducts as alternative fueland raw materials (AFR). This very large volume is morethan double the amount of waste going into landfill inJapan (around 13 million tons in 2012). The following
discusses the kinds of waste and byproducts recycled bycement plants and how this is possible.

possible to use waste tires, waste oil and waste plastic as
auxiliary fuel (alternative fuel) for cement burning, due totheir high calorific value (see Table 9.1).
Table 9.1 Typical Composition of Main Waste Materials
and Byproducts 3)
Cement raw
material(waste andbyproducts)

Calciumoxide
CaO

SilicondioxideSiO2

Aluminum
oxide
Al2O3

Ferricoxide
Fe2O3Coal ash5~20%

40~65%

10~30%

3~10%

Incinerationash

20~30%

20~30%

10~20%~10%

Biosolids

5~30%

20~30%

20~50%

5~10%

Casting sand

~5%50~80%

5~15%

5~15%

~10%

5~20%

10~20%~5%

Waste tires
Blast-furnace
slagTypes of Waste and Byproducts used in the
Cement Industry 3)
Manufacturing cement clinker requires raw materials
primarily containing calcium, silicon, aluminum and iron.
Previously, most of these had to come from natural
materials. However, if waste and byproducts containthese compounds, it is possible to use them in place of
natural raw materials (alternative raw materials). It is also95

20~45%

The cement industry developed the technology to use
various waste matter and byproducts as alternative fueland raw materials (AFR) (Figure 9.1). In 2012, the total
amount of waste and byproducts accepted by cement
plants reached around 28.5 million tons per year,
corresponding to 481kg of waste/byproduct used per tonof cement (Figure 9.2, Table 9.2). Of these, the mostcommonly used materials were blast-furnace slag andcoal ash, as shown in Table 9.2. Around one third of
blast-furnace slag generated and around half of the coalash emitted by coal-fired power plants is used by the
cement industry as an additive or raw material.
9.1.2

The Reason the Cement Manufacturing
Process is Suited for Waste Disposal 3)
The cement industry recycles a great variety of waste
matter as raw materials or fuel for cement manufacturing.
This recycling is possible due to the following
manufacturing advantages.
(1) Cement kilns have a very high burning temperature,
meaning dioxins, fluorocarbons and other harmful
substances break down and become harmless.
Thermalpower plants

9.1.1

30~60%

Ironworks

Coal ash, flue gas desulfurization
gypsumSewage treatment plants

Biosolids,
incineration ash

Blast-furnace slag, steel slag

Waste liquid, waste clay

Food factories

Construction site sludge,
construction site soil

Construction
sites

Incineration ash

Garbageincineration plant

Automotive
repairers

Waste tires

Paper mills

Paper sludge
Cement plants

Oil refineries

Waste oil, recycled oil

Casting sandFoundries

Smelters

Non-ferrous slag

Meat­and­bone meal

Rendering plants

Various plants
and enterprises

Waste plastic

RDF, RPF

Garbage solidifying
fuel plants

Fig. 9.1 The Resource Recycling System Centeredaround Cement Plants 3)

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March(kg/t-cement)(10,000t)

Year
Cement production volume
Waste/byproduct usage volume
Amount of waste/byproduct used per
ton of cement

Fig. 9.2 Trends in Waste/Byproduct Usage Volume andCement Production Volume 3)(2) The cement industry effective energy utilization
rate is very high at 80% (see Figure 5.13), a far
higher energy utilization rate than incinerating
waste with an incinerator.
(3) The ash left over from burning waste matter forms
part of the raw materials for cement, burned in arotary kiln to produce cement clinker. Accordingly,
the utilization of waste at cement plants does not
involve the generation of secondary waste
However, cement kilns need to be closed for several
consecutive weeks of the year (scheduled closure) for
repair and maintenance of the firebrick lining inside.
Although storage of blast-furnace slag, coal ash,incineration ash, waste tires and waste plastic during thattime is not a major problem, there needs to be adequate
advance consideration on how to manage the receiving of
biosolids and raw garbage during the closure period. Thisis easy to handle for plants with multiple kilns, but plants
with only one kiln have to divert it to another plant ownedby the company. In some cases, they may have the optionof diverting it to a plant owned by another company
through inter-plant cooperation.
Certain types of waste matter, such as incineration ash
and waste oil, can contain heavy metals or other harmful
substances. Consequently, cement plants make thoroughchecks on the following to verify safety before making oncontracts to accept waste.
1 There is no possibility of harmful substances being
released into the atmosphere during the cement burning
process.
2 There is no possibility of harmful substances being
eluted in wastewater or into the soil when the cement isused as concrete or as a soil stabilizing material by theuser.
It takes all the manufacturing technology know-how
and the cement chemistry knowledge that have been built
up over the years to carry out these tests and checks. Even
after a plant has started accepting waste, frequent strict
checks are carried out to ensure the waste being deliveredis in accordance with the contract agreement and toensure the emissions and the product quality meet thecontrol criteria.
The following discusses newly developed technologies
for safely utilizing large volumes of waste matter in the
cement manufacturing process.
Many of the waste materials and byproducts given in
Table 9.2 can be used directly in the cement
manufacturing process without any particularpre-processing. For example, this includes blast-furnaceslag, coal ash, byproduct gypsum, casting sand, steel slag,
waste tires and coal waste.

Table 9.2 Main Applications and Usage Volumes of Waste and Byproducts used in the Cement Industry 4)(unit: 10,000t)
Main
application

Type
Blast-furnace slag
Coal ashadditive, rawmaterial
raw material,
additive

1990

1995

2000

2005

2010

2011

2012

2013

12,22812,486

12,162

9,214

7,408

8,082

8,485

8,995

2,021

3,103

5,145

7,185

6,631

6,703

6,870

7,333
3,206

Sludgeraw material

312

905

1,906

2,526

2,627

2,673

2,987

Construction soil

raw material

-

-

-

2,097

1,934

1,946

2,011

2,407

Byproduct gypsum

raw material(add-in)

2,300

2,502

2,643

2,707

2,037

2,158

2,286

2,401

Combustion residue(other than coal ash),soot, dust

raw material

478

487

734

1,189

1,307

1,394

1,505

1,405

Non-ferrous slag

raw material

1,233

1,396

1,500

1,318

682

675

724

770

Wood chips

thermal energy

-

-

2

340

574

586

633

657

Casting sandraw material

169

399

477

601

517

526

492

461

Waste plastic

thermal energy

-

-

102

302

418

438

432

460

Steel slag

raw material

779

1,181

795

467

400

446

410

423

Waste oilthermal energy

141

107

120

219

275

264

273

273

Waste clay

thermal energy

41

94

106

173

238

246

253

273

Recycled oil

thermal energy

0

126

239

228

195

192

189

186

101

266

323

194

89

73

71

65

-

-

0

85

68

64

65

63

Waste tires
Meat and bone meal
Coal waste

raw material,
thermal energy
raw material,
thermal energy
raw material,
thermal energy

1,600

1,666

675

280

0

0

0

0

Other

-

361

379

431

468

595

606

835

887

Total

-

21,76325,09727,35929,59325,99527,07328,52330,265

251

257

332

400

465

471

481

486

Amount used per ton of cement (kg/t)

Note) Construction soil is included under “Other” until 2001.

History of Cement Manufacturing Technology

969.2 Waste Recycling Technology in the Cement
2)

Industry
There has been growing demand since the 1990s for
cement plants to process waste that is difficult to recycle
using conventional waste disposal technology. Cementcompanies have redoubled their efforts in research anddevelopment of environmental technologies. This section
discusses technology developments by the Japanese
cement industry and the main recycling technologies
implemented.
9.2.1
Alternative Fuel from Waste Tires 2)
Since 1978, Nihon Cement and Bridgestone have been
jointly researching the effective utilization of waste tiresin the cement manufacturing process. Suspension
preheaters were fitted with feed chutes for waste tires.
The calorific value of these tires contributed up to 15% of
the total fuel used. The technology was then developed tofeed the tires directly into rotary kilns without crushingthem first. The technology was patented 5), paving theway for large volumes of waste tires to now be effectively
utilized by cement plants (Figure 9.3).

Fig. 9.3 Cement Kiln Whole Tire Conveying Device 3)This technology has the following five distinguishing
characteristics.
1 Little concern over preheater coating buildup or
cyclone blockage. In addition, no hindrance to stablelong-run operation because of no increase of exhaustgas temperature.
2 Cost-effective and no issue with noise or vibrationfrom crushing, as waste tires are used as they arewithout processing
3 No secondary pollution from incinerating waste tires.
In addition, the NOx emissions from conventional
cement burning are reduced.
4 No effect at all on the quality of cement produced
5 Even tires containing steel can be used as they are(iron content used as a raw material)

97

Chlorine Bypass 6) 7): A Major Invention that
Paved the Way for Large-Volume Waste
Disposal at Cement Kilns
The chlorine, alkalis, sulfur and other volatile
substances brought in from the cement raw materials andfuel circulate within the kiln and preheater. This
circulation eventually builds up concentrations ofespecially the chlorine content to around 150 times
greater, producing a low-melting-point substance that
forms a coating on the inner wall of the preheater. This
results in issues such as ventilation resistance and cyclone
blockage, thus hindering the stable operation of the kiln.
While advances were being made in using waste matter
aimed at environmental conservation and effective
utilization of resources, it also meant an increasing
amount of volatile substances, particularly chlorine, wasbeing put into the cement burning system. Technology
needed to be developed that would effectively eliminate
this chlorine, both for stable kiln operation and forincreasing the amount of waste intake.
Under these circumstances, Chichibu Cement
developed a unique “chlorine bypass system” that would
effectively remove the chlorine from the kiln andpreheater system. The first system was installed on a kiln
at the Chichibu plant at the Chichibu plant in 1990.
The chlorine bypass system uses a carefully-designed
probe (flue gas aspirator) to draw some of the gas out of
the kiln. This gas is then rapidly cooled to thesolidification point for chlorine compounds, allowing thechlorine compounds to solidify and be extracted andremoved. The system has the following features:
1 Since it is specifically positioned at and extracts
from the point where the most chlorine compounds
condense and where there is low dust concentration,
the majority of the chlorine brought into the system
can be removed with an extremely low extraction
rate. Meanwhile, it does not readily attract dust
containing useful cement compounds, meaning very
little thermal loss.
2 Since the extracted gas is immediately cooled to
below 300ºC, there is little chance of dioxins
reforming.
3 The system has a cyclone apparatus for theappropriate particle size separation, which returns
particles with low chlorine content to the kiln. As aresult, the remaining amount of chlorine-containing
dust taken out of this system is less than 0.1% of theamount of clinker produced. This small amount canbe absorbed into the process by adding it to thecement in the finishing process.
The development of the chlorine bypass systemsignificantly increased the industry’s capability to processwaste matter containing chlorine. For example, waste
plastic high in vinyl chloride was often refused in the past,
but is now far more commonly accepted by plants with
9.2.2

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchchlorine bypass systems installed. Previously, the amountof chlorine entering the kiln system was limited by theconstraining factor of preheater coating buildup and other“process issues”. Now, the JIS regulation on chloride ionshas become restriction against processing waste bycement kilns (see 8.2.2 (7)). Not only is this systeminstalled on all kilns owned by its developer Chichibu
Cement and Taiheiyo Cement after the companies merged,
it is also being widely adopted by other cementcompanies in Japan and overseas through the technology
licensees Taiheiyo Engineering and Technip (the main
engineering company in France). This system
dramatically reduced the process issue of cyclone
blockage due to buildup of low-melting chlorides, thedrawback with the SP and NSP systems. It is one of thegreatest Japanese inventions paving the way forhigh-volume waste disposal by cement kilns.
9.2.3
Alternative Fuel from Waste Plastic 2) 8)
While “waste plastic” is a simple term, there is anendless variety of plastic waste, of all different types,
shapes and contamination levels. Therefore, it is a generalpractice that the local governments and companies that
discard plastic work together with the cement plants thatcollect the plastic to determine the methods of intake andthe facilities for intake, such as crushers. The following
discusses the case of Tokuyama, which developed thetechnology to incorporate waste plastic as an auxiliary
fuel for rotary kilns, and the case of Taiheiyo Cement,
which developed the technology to utilize waste plastic asan auxiliary fuel for preheater calciners.
In 1992, Tokuyama (Yamaguchi Prefecture) became
the first cement manufacturer to start developing
technology to use waste plastic as fuel as a means ofrecycling plastic. The company developed the technology
to blow large volumes of crushed plastic into the front of
the rotary kiln quite stably and in 1999 set up a waste
plastic fuel conversion (crushing) plant (crushingcapacity: 15,000t/year). This technology won thecompany the Award of the Director-General of the METI
Industrial Science and Technology Policy andEnvironment Bureau in 2002. Later, the company
successively expanded its plant facilities as the demand
grew to accept more waste plastic. As at 2015, the plant
had expanded to be capable of crushing and burning
125,000 tons of waste plastic per year.
The other example is that of the Taiheiyo Cement
Kumagaya plant (Saitama Prefecture) developing thetechnology to accept waste polyethylene film.
This technology was developed for use as auxiliary
fuel for suspension preheater calciners. Combustion
testing was conducted by electric furnace, while thermal
analysis was carried out by heat flux simulation todetermine the spatial combustion conditions. As a result,the following knowledge was acquired.
1 Polyethylene with very little fixed carbon content
combusts in the form of gasified combustion,equivalent to droplet combustion.
2 The blowing speed is important to the spatial
combustion of polyethylene particles in the calciner.
At 20m/sec, if the polyethylene particle massexceeds 0.5mg, the particles collide with the furnacewall. At 10m/sec, the particles can have a mass of up
to 3.5mg; at 5m/sec, it can be up to 4.0mg.
Based on the above preliminary experiments, waste
plastic pre-processing facilities were established in 1999.
Once initial issues with contamination and crushedmaterial consistency were resolved, the facilities havecontinued to operate stably.
9.2.4

Technology to Use Biosolids for Alternative
Fuel and Raw Materials (AFR) 2)
Cement companies use biosolids as AFR in accordancewith different factors, such as plant location and available
sewage treatment facilities. The biggest issue is dealing
with the smell and matters of hygiene. In addition, thekiln system needs to have strict arrangements in place for
dealing with these issues during operation stoppage
periods. Biosolids are usually transported directly fromsewage treatment facilities to closed tanks at the cement
plant by closed-tank trucks, such as arm-roll trucks. The
biosolids are then fed directly into the kiln.
9.2.5

Technology to Use Municipal Waste for
Alternative Fuel and Raw Materials (AFR) 2)
Most municipal waste is incinerated, with theincineration residue (incineration ash) disposed of into
landfill. However, with the shortage of landfill site
becoming an issue in the 1990s, there was a pressing needto develop the technology to reuse municipal waste. The
following three technologies were developed to use
municipal waste as AFR, in response to social demand.
All of these later went into operation at actual plants andhave contributed significantly to a sustainable
resource-recycling society.
(1) Ash washing system(2) Ecocement(3) AK system
All of these three technologies were developed inJapan and contribute to a sustainable resource-recycling
society. In future, as other countries and regions
experience issues with municipal waste as Japan has,
there will be opportunities to license these technologies
overseas.

History of Cement Manufacturing Technology

98

(1) Ash washing system 2)
Figure 9.4 shows a flow diagram of a typical ash
washing system.
When incineration residue is used as a raw material forPortland cement, the biggest issue is the chloride content
of the incineration residue. Incineration residue can be
categorized two ways: bottom ash (incineration ash,primary ash) and fly ash (dust and soot). Bottom ash has a
low chloride ion content of around 0.4-3%. By using the“chlorine bypass” that reduces vaporized chlorides, it ispossible for cement kilns to use this ash directly in the
cement without dechlorinating it. Meanwhile, fly ash hasa high chloride ion content of around 5-20%, meaning it
cannot be used directly in the cement kiln without
pre-processing; it needs to be dechlorinated before being
used in the cement kiln. Noting that most of the chlorides
in fly ash are soluble, researchers at Chichibu Onoda(now Taiheiyo Cement) started developing the technology
to dechlorinate fly ash by washing it. The following is an
overview of the course of this development.
Waste incinerators include stoker furnaces andfluidized bed furnaces. Laboratory testing of fly ash fromeach type of furnace from several different incineration
plants showed that while almost all of the chlorides could
be removed from some types of fly ash by washing alone,depending on the fly ash, some chlorides formed
insoluble Friedel’s salt (3CaO·Al2O3·CaCl2·10H2O) thatshowed a low dechlorination rate when only washed withwater. However, Friedel’s salt was known to break downin acidic solutions. Experiments verified that washing fly
ash suspension while blowing it with carbon dioxide hada high dechlorination rate. It was also found that blowing
it with kiln exhaust gas would not only break down theFriedel’s salt, but would also cause the eluted calcium
ions to bond with the carbonate ions, forming calcium
carbonate. It was thus proven that the carbon dioxide in
the kiln exhaust gas could be used to achieve a highdechlorination rate even on fly ash containing Friedel’ssalt. It was also confirmed that all heavy metals except
mercury were below detectable levels in the secondary
filtrate generated from washing and filtrating fly ash andthen blowing it with kiln exhaust gas to adjust its pH level
to between 7.2 and 10.2.
It was shown that the longer the fly ash was humidified,
the further the solidification progressed due to thehydration reaction, and the higher the Friedel’s saltcontent. Accordingly, waste incineration plants wererequested to supply fly ash to cement plants in a driedstate.
Based on laboratory testing of the above, a fly ash
washing and dechlorinating test plant was designed andthen built at the Kumagaya cement plant in 1998 (Figure9.5). Fly ash from the Kumagaya Sanitation Center with a
15% chloride ion concentration was treated by washingand dechlorinating. The resulting cake contained achloride ion concentration of 0.5% or less, thus achieving
a dechlorination rate of 97%.

Fig. 9.5 Ash Washing Facility 10)

The washing and dechlorinating filtrate was neutralizedwith kiln exhaust gas.

Ash washing / foreign matter removal
process
Ash washing process (dust)
Belt filter
Water

Solution
Dehydrated cake

Dust

Wastewater treatment process

Dissolution tank
Filtrate

Harmless
wastewater

Fuel

Magnetic separator

Foreign matter removal
process (incineration ash)

Sieve

Incineration ash

CrusherCoarse

Metal

Fine

Large lump remover
RecyclePreheater

Fig. 9.4 Ash Washing System Flow Diagram 9)99

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

Finishing process

Rotary kiln for burning

Compatible
matterOther treatments to further ensure its safety included
treatment with liquid chelate, advanced filtration using
sand filtration and treatment with mercury chelate resin.
With analysis of the wastewater confirming that all values
complied with regulatory values, “fly ash washing system”
technology was implemented. The filter solids after
washing and the solids produced by precipitating,separating and filtering the pH-treated filtrate were used
as cement raw material, with the treated wastewaterdrained into the sewage system.
(2) Ecocement 2)
Like “ash washing”, “ecocement” was developed withthe aim of recycling the incineration ash from municipal
waste and biosolids into cement raw material.
When municipal waste incineration ash is used as
cement feedstock, the chlorides in the ash can
detrimentally affect the quality of the final cement
product, as discussed previously. The first step indeveloping ecocement was to develop rapid-hardening
ecocement using chloride as a constituent element incalcium chloroaluminate (11CaO·7Al2O3·CaCl2).
However, having only a rapid-hardening product meant
limited applications for the product (cement).
Development continued with the aim of developing amore versatile cement. Isolating and removing chlorides
and heavy metals during the manufacturing process
resulted in the development of “ordinary ecocement” witha chloride content lowered to a level similar to that ofordinary Portland cement.
Test production of ecocement was taken on as a MITI
(now Ministry of Economy, Trade and Industry: METI)“lifestyle industrial waste processing/utilizing technology
research” project in 1994. Research and development
began on “ecocement production technology to utilize
general municipal waste”, with funding provided by the
Ecocement system flow

government. Based on the test production results, thefully industrial Ichihara Ecocement Plant commenced
operation in 2001 in Ichihara, Chiba Prefecture, as theworld’s first ecocement facility. The plant can produce
around 110,000 tons of ecocement per year, withincineration ash feedstock provided from the waste of 1.5
million people, around quarter of the population of Chiba
Prefecture. In 2006, the Tokyo Tama Ecocement Facility
started operating in Hinode, Nishi-Tama, Tokyo,
processing the ash from incineration plants for 25 cities
and 1 town in the Tama area of Western Tokyo. It
produces 110,000 tons of ecocement per year from its
primary raw material of waste incineration residue(around 90,000 tons per year) generated in the Tama area
(population around 3.9 million). Figure 9.6 shows aphotograph of the Tokyo Tama Ecocement Facility, while
Figure 9.7 shows a flow chart of the facility.
Incineration ash (primary ash) and incineration fly ash(dust) from the municipal waste incineration plants isreceived by the ecocement plant, where it is blended,
dried and ground in a vertical mill with the limestone andother natural raw materials. Once powdered, it is pumped
into the raw material homogenizing tank. The
homogenized raw material is sent to the rotary kiln to be
burnt at 1350°C or higher to form clinker, thesemi-processed form of cement.

Fig. 9.6 Tokyo Tama Ecocement Facility 11)

Metal, glass, etc.

For recycling

To recycling

To smelting plant

CopperLead

Raw materialflow
Gas flow

Denitrification
tower

Heavy metals recovery system

Smokestack

Zinc
Bag filter

Municipal
waste

Bag filter

Incineration
plant

Shipping tank
Homogenizing
tank

Grinding mill

CycloneIncineration
ash
Dust

Cooling tower

Tank

GypsumClinker

Ecocement

Rotary kiln

Supplementary materials (limestone, etc.)

Drying and grindingmill

Fig. 9.7 Ecocement Manufacturing Process 9)

History of Cement Manufacturing Technology

100The clinker is blended with gypsum to produce
ecocement. The exhaust gas from the burning process iscooled in the cooling tower and the dust is removed bycyclone and bag filter. The nitrogen oxide is removed in
the denitrification tower and is released into theatmosphere. Since the dust collected in the bag filter
contains chlorides containing heavy metals, it is sent to
the heavy metals recovery system (discussed later in
9.2.6) and recycled as “artificial ore” containing copper,
lead and zinc.
The ecocement manufacturing process differs
significantly from that of ordinary Portland cement in thefollowing three ways.
1 The raw materials are fed directly into the kiln rather
than through a preheater, in order to decompose thedioxins immediately.
2 The cooling tower prevents dioxins fromresynthesizing.
3 Heavy metals are recovered and chlorides removed
through a chloride volatilization process, allowing
the heavy metals to be extracted from the heavy
metal chlorides and recycled.
Ecocement manufactured by the above process wasstandardized under the JIS in 2002. It has two types:“ordinary ecocement”, which has properties similar toordinary Portland cement, and “rapid-hardening
ecocement”, which has rapid hardening properties.
The quality standards for ordinary ecocement arelargely the same as for ordinary Portland cement. The
only difference is the upper limit for sulfur trioxide (SO3)and chlorine ion content. Even in terms of the upper limit
for chlorine ion content (0.035% or less for ordinary
Portland cement, 0.1% or less for ecocement), it isgenerally possible to take the view that “ordinary
ecocement is almost identical in quality to ordinary
Portland cement”, considering that the standard forchlorine ion content in ordinary Portland cement inEurope is 0.1% or less (EN 197:2000), although someattention should be paid to the chlorine ion content of theconcrete.
Rapid-hardening ecocement hardens more rapidly thanhigh-early-strength Portland cement. Although it
demonstrates high-early-strength properties and can beused in the area of unreinforced concrete, as at 2015 it is
not in production.
(3) AK System 2)
The ash washing system and ecocement aretechnologies that use incineration residue of municipal
waste from incineration plants as cement raw materials.
However, in recent years, there have been concerns overdioxins and it has become more difficult to constructincinerators. The Applied Kiln (AK) System wasdeveloped by Taiheiyo Cement to enable cement plants to101

accept municipal waste in its original state for cement raw
materials. The system has been operating commerciallysince 2002. The following is a summary of thisdevelopment.
The municipal waste decomposing process at the coreof the system is based on rotary kiln aerobic fermentation
technology owned by Bedminster AB (Sweden), which
has achieved results in the United States and othercountries. While prior investigation showed that there
were significant advantages to using the company’s rotarykiln Eweson Digester for the municipal waste cement
feedstock process, the following had to be validated
before introducing the technology.
(1) Can the technology process Japanese waste thesame way?
(2) Some Japanese operations also have the capacity
to process only municipal waste without biosolids.
Does the technology demonstrate the same effectwhen processing only municipal waste?
In order to validate the technology, validation testing
was carried out in December 1999 using a
Bedminster-owned facility (located in Sweden). The main
waste used for the testing was collected from the area
near the testing facility, modified to be similar incomposition to general combustible waste from Hidaka,
Saitama Prefecture, where the first actual plant wasplanned. The testing facility waste was put into plasticbags and deposited directly into the digester. After threedays of fermentation processing, the contents had allcome out of the bags and the bag-breakdown effect wasdeemed adequate. Corrugated cardboard and disposable
diapers were also deposited directly into the digester andcame out broken down into pieces after processing. Dueto this superior ease of handling, the shredding down
effect was also confirmed. The coliform count of thefermentation product was less than 2.5 × 102 MPN/g (dryweight), fully compliant to the US EPA safety standard
for composted product pathogenicity of 1.0 × 103 MPN/g(dry weight). This suggested that the increase intemperature in the digester (45-50°C after one day) could
sterilize the pathogens in municipal waste. The test results
confirmed that the Eweson Digester could be used in themunicipal waste cement feedstock process. A technology
license contract was signed with Bedminster in July 2000
for the Eweson Digester and the know-how to operate it.
Based on this fermentation technology, Taiheiyo
Cement established its own AK system technology withthe basic design ideas below.
1 Garbage from both household and industry is
accepted directly by the cement plant;
2 Wastes are aerobically fermented in a “feedstockkiln” modified from a cement burning kiln;

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

3 Recycled into cement raw materials.
Verification testing of the municipal waste cement
feedstock process using the AK system started in March
2001 and continued for one year at the Taiheiyo Cement’s
Saitama Plant in Hidaka. The plant started commercial
operation in November 2002. Figure 9.8 shows aphotograph of the entire AK system. For the City of
Hidaka, it meant no more rebuilding of deteriorated
incinerators, with all general combustible waste sent toTaiheiyo Cement for disposal. For the cement plant, thiswas a chance to reutilize kilns that were no longer used
due to reduced demand and convert them to resource
recycling kilns.

Fig. 9.8 AK System: Taiheiyo Cement Saitama Plant 9)
The rotary kiln on the left is the waste feedstock kiln; therotary kiln on the right is the cement burning kiln.

Figure 9.9 shows the cement manufacturing processusing the AK system. In the AK system, municipal waste
brought directly into the cement plant is first transported
to the feedstock kiln in the fermentation process. Inside
the feedstock kiln, the garbage bags break down and thewaste converts into odorless, easily-handled “feedstock
matter” that is easily screened, magnetically separated
and crushed. In the following crushing and separatingprocess, any metals in the feedstock matter are removed
by magnetic separator and the remainder crushed to a
manageable size of 30-40mm. In the following burning
process, the plastics and other combustible content in thefeedstock matter is effectively utilized as alternative fuelfor cement burning. Meanwhile, some of the incineration
residue is burned in the rotary kiln and put into the clinker(alternative feedstock). Since the cement burning kiln
operates continuously at a high temperature of 1450°C,
no dioxins or other harmful substances are generated byburning the municipal waste.
Thus, the AK system makes waste incinerators andfinal disposal sites unnecessary and also prevents thegeneration of dioxins from incineration. As a result, thesystem has attracted wide attention as a new waste
disposal technology suited to a resource-recycling
society.
9.2.6

Technology for Extracting Heavy Metals
from Chlorides 2)
Until the 1990s, cement plants mainly accepted wastethat was low in chlorides or heavy metal content.
However, as the cement plant industry’s resource
recycling business expanded, the demand has grown for
accepting waste matter that contains high chlorides or
heavy metals, such as incineration ash. Accordingly,
efforts have been made to develop technologies that focus
on the heavy metals in chlorides as well as
chloride-focused technologies such as the ash washingsystem and ecocement. The following is an outline oftechnology for extraction of heavy metals from chlorides,
generated at ecocement plants.
In the ecocement manufacturing process, heavy metals
contained in the feedstock of waste incineration ash
undergo chloride volatilization in the rotary kiln during
the burning process and are collected in the bag filter. An
extraction system was developed in which lead, zinc andcopper are extracted from the collected chlorides andrecycled as raw materials for non-ferrous smelting, while
calcium and other compounds are reutilized as cement
feedstock. This Heavy Metal Extraction (HMX) system ismade up of the following five processes.
1 Dealkalization process: The heavy-metal-containing
chlorides collected in the bag filter are mixed withwater to elute the soluble chlorides (NaCl, KCl),
which account for around 80%. This reduces thesolid content volume to around one-fifth, allowing
the equipment for the following processes to be
more compact.
2 Copper ion and zinc ion elution process: The
solid-liquid separation residue from the
dealkalization process has sulfuric acid added to it toelute the copper ions and zinc ions.
3 Lead ion elution process: The solid-liquid separation
residue from process 2 has a sodium hydroxideaqueous solution added to it to elute the lead ions.
Since the remaining residue is calcium hydroxide, it
is returned into the cement feedstock.
4 Lead, copper and zinc compound separation process:The solid-liquid separated filtrates from processes 2
and 3 is pH adjusted to separate and remove the lead,copper and zinc compounds.

History of Cement Manufacturing Technology

102Holding tank

Deodorization
Garbage truck

RecycledmatterWaste feedstock kiln

Incinerating
plant

Not
neededCrushing, screening,
separating

Receiving room
(sealed)Clinker silo

GypsumPreheater
Deodorizer(for
no-operation
period)Dustcollector
Limestone

CoalintakeClay
SilicaFerrousmaterialRawmaterial
grinding millCement burning kiln

BurnerCement grinding mill

Raw mix
silo

Cement silo
Clinker cooler

Dispatch

Fig. 9.9 Cement Manufacturing Process using the AK System 9)

5 Wastewater treatment process: The wastewater fromprocess 4 is treated to meet the effluent water
standards.
Since the residue from process 2 contains calcium,
calcium sulfate is produced by reacting it with an aqueous
sulfuric acid solution. As a result, the main compound in
the residue obtained by solid-liquid separation in process
2 is calcium sulfate containing small amounts of leadsulfate. The sodium hydroxide aqueous solution added inprocess 3 not only elutes the lead ions, but also acts totransform the calcium sulfate into calcium hydroxide.
While it is still a calcium compound, calcium hydroxide
is preferable to calcium sulfate in cement. This method ofallowing residues to be recycled into cement feed is amajor advantage to the HMX system. A mini plant wasestablished while the technology was gathered to scale it
up. The Tokyo Tama Ecocement Facility adopted thesystem in 2006.
9.2.7

Decomposition of Fluorocarbons: The
World’s First Decomposition Technology
Using a Cement Kiln 2)
Since the 1990s, many countries including Japan haveplaced strict legal regulations on fluorocarbons as
substances that destroy the ozone layer. A major issue has
been the establishment of technology that will decompose
fluorocarbons safely and reliably. Chichibu Onoda
Cement (now Taiheiyo Cement) started joint researchwith the Tokyo Metropolis in 1994 with the aim ofcreating such technology using a cement kiln. This
resulted in the world’s first successful use of a cementkiln to decompose fluorocarbons. The cement kiln
method was one of the technologies accepted at a
Meeting of the Parties to the Montreal Protocol on

103

Substances that Deplete the Ozone Layer. The treatment
method is outlined below.
Since fluorocarbons decompose at 900°C or higher,
inserting them into a cement kiln with a burning zone
temperature of around 1500°C causes the breakdown
reaction shown in formula (1), generating hydrogenchloride and hydrogen fluoride.
CCl2F2(CFC-12) + 2H22ĺ+&O+)&22 ···· (1)The acidic gas of the generated hydrogen chloride andhydrogen fluoride passes through the cement kiln and isabsorbed into the bases in the cement raw materials anddust. Reactions (3) and (4) take place, generating calcium
chloride and calcium fluoride, which are eventually
incorporated into the cement.
CaCO3 OLPHVWRQH ĺ&D2&22 ····················· (2)&D2+&Oĺ&D&O+2O ·························· (3)&D2+)ĺ&D)2 + 2H2O ···························· (4)This process has significant advantages. It has anextremely high decomposition efficiency of 99.99% orhigher. Also, since the harmful gases mentioned above(hydrogen chloride and hydrogen fluoride) generated by
the decomposition of the fluorocarbons are incorporated
into the cement, there is no need to treat the exhaust gas.
The technology was put into operation at Taiheiyo
Cement’s Chichibu No. 2 plant, but fluorocarbon disposal
had to stop when the plant discontinued cement
production (September 2010) due to reduced demand for
cement.

9.3 Cement Plants Active in Waste Processing
from the Great East Japan Earthquake

12)

In the Great East Japan Earthquake of March 2011, themajor earthquake and accompanying tsunami caused

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. Marchunprecedented major damage across a vast area of the
Pacific coast. The disaster left behind all kinds ofearthquake and tsunami waste and deposits in 239 cities,
towns and villages in 13 prefectures (excluding theevacuation area in Fukushima). Earthquake waste
amounted to 20.188 million tons, while tsunami deposits
amounted to 11.016 million tons across 36 cities, towns
and villages in six prefectures. The waste matter wascontaminated with salt from the tsunami, which was amajor obstacle in the subsequent reconstruction process.
In Iwate Prefecture, the disaster waste disposal plan
centered on “processing of disaster waste at cement plants
in and out of the prefecture as cement feedstock”. There
were three reasons for this:
1 It is possible to process large volumes of disaster
waste rapidly and in a short period of time using
existing facilities.
2 It reduces the amount of disposal sites needed fordisaster waste incineration ash.
3 The cement manufactured at the waste processing
stage can be supplied as a rebuilding material.
7DLKHL\R&HPHQW¶VƿIXQDWRSODQWLQƿIXQDWR,ZDWH
Prefecture, sustained substantial damage from the tsunami
and was unable to operate. However, efforts were made tostart rebuilding the plant at the same time as theprocessing of disaster waste. A “disaster waste
desalination system” was developed that made it possible
to use salt-contaminated disaster waste as cement raw
materials. Working facilities (Figure 9.10) were
established and started operation. By March 2014, at theend of the contract period agreed with the prefectural
government, the plant had received and processed morethan 950,000 tons of disaster waste.
This system produced four types of desalinated disaster
waste: soil, sand, combustible material and incombustible
material. The soil and sand were improved to conform to
the Iwate Prefecture disaster waste recycling manual. A
new project was commenced for processing disaster
waste into earthworks material for the rebuilding of theprefecture. This initiative and the cement feedstock
initiative made it possible to increase the amount ofdisaster waste processed.

Fig. 9.10 Disaster Waste Desalination System at Taiheiyo&HPHQW¶VƿIXQDWR3ODQW SKRWRJUDSKHGE\WKe author)

To cover vast disaster areas, other cement plants in the7ǀKRNXUHJLRQ0LWVXELVKL0DWHULDOV¶,ZDWHSODQW(Ichinoseki) and Hachinohe Cement (Hachinohe, Aomori
Prefecture), assisted in the processing of a variety ofdisaster waste. Taiheiyo Cement’s Kumagaya andSaitama plants and Mitsubishi Materials’ Yokoze plant(Chichibu, Saitama) and Aomori plant (Hachinohe)assisted from afar with the processing of wood chips.
7KXVFHPHQWSODQWVLQWKH7ǀKRNXDQG.DQWǀDUHDV
contributed to the processing of disaster waste.
In the spring of 2013, Their Majesties the Emperor andEmpress came to inspect the rebuilding of thedisaster-DIIHFWHGDUHDLQWKH7ǀKRNXUHJLRQ7KHWRXU
LQFOXGHGDYLVLWWR7DLKHL\R&HPHQW¶VƿIXQDWRSODQWDQG
observation of disaster waste processing in operation.
This imperial visit was regarded as an honor for the wholecement industry, a major event carried out because thenation, the prefecture and the local community highly
regarded the contribution of cement plants to disaster
waste disposal.
Note 1: Industrial waste and byproducts“Alternative fuel and raw materials purchased for a price” bycement plants are termed “byproducts”, while “alternative fueland raw materials received with a processing fee” are termed“waste”. Examples of byproducts include blast-furnace slag andbyproduct gypsum.

References (all in Japanese)
1) Takashi Shimoda, “Cement R & D in the Cement
Industry Toward the 21st Century”, Cement &Concrete, No. 635, pp.2-9, 2000.
2) Keiichi Miura, “Research and Development ofEnvironmental Technologies”, Journal of Researchof the Taiheiyo Cement Corporation, No.150,
pp.57-75, 2006.
3) Japan Cement Association, Introduction to Cement &Concrete, 2013.
4) Japan Cement Association, Cement Handbook, 2014.
5) Shoichi Tsuda, Motokazu Kikuchi, Tadatoshi
Shimazaki, Toshio Tsuji, Shunro Ueda andMasamichi Kabaya, Patent Application No. 1-32175,“Manufacturing Method for Cement Clinker”.
6) Mitsuhiro Ito, “R & D for Effective Cement
Manufacturing”, Journal of Research of the Taiheiyo
Cement Corporation, No.150, pp.29-56, 2006.
7) Naoki Ueno, Hiroshi Harada, Kanzaburo Suto,“Chlorine Bypass System for Stable Kiln Operationand the Recycling of Waste”, Cement & Concrete,
No. 634, pp.28-35, 1999.
8) Tokuyama Corporation website, October 2015.
9) Supplied by Taiheiyo Cement Corporation.
10) Taiheiyo Cement website, September 2015.
11) Supplied by Tokyo Tama Wide Area Resource
Recycling Association.
12) Hideki Kondo, “Role of the Cement Industry”,
Concrete Journal, Vol.53, No.1, pp.97-101, 2015.

History of Cement Manufacturing Technology

10410 Summary: Systematization of Cement
Manufacturing Technology

The major course of cement manufacturing technology
development discussed in the above chapters through to
Chapter 9 is summarized in the appended diagram“Systematization Diagram of Cement Manufacturing
Technology in Japan”. To keep it simple, the diagram
focuses on Japanese cement manufacturing technology.
Western cement manufacturing technology inventions
and developments, from the invention of Portland cementin the United Kingdom at the start of the 19th century
through to the mid-20th century, are adequately
understood by examining the development of theJapanese technologies based on them. Japan had drawn
even with the West by the mid-20th century and then fromthe 1980s onwards led the world. The appended table“Chronology of Cement Manufacturing Technology” isprovided at the end of the report to help readers
understand this course of events.
From the invention of Portland cement to the presentday, the greatest driving factors for advances in cement
manufacturing technology have always been the pursuitof energy-saving and ensuring a consistently high-quality
product. Accordingly, this systematization of thetechnology is also taken mainly from these two angles.

10.1 Burning Process: Technology
Development Goals of Saving Energy
and Producing High-Quality Clinker
When Portland cement was first invented, it wasbatch-produced in shaft kilns. Even Japan’s first cement
plant, the Fukagawa Cement Works, produced
inconsistent quality during the shaft kiln era, with thehigher quality product having to be screened from theclinker coming out of the kiln. The development of therotary kiln at the end of the 19th century enabledcontinuous burning of clinker. The rolling movement of
the raw materials within the kiln also improved theburning reaction and made it possible to mass produce
high-quality cement. However, the rotary kiln had thesignificant drawback of poor thermal efficiency. The
main causes of heat loss were heat escaping with theexhaust gas and heat escaping with the clinker.
Technology developments to improve the thermal
efficiency of rotary kilns focused on these two points.
(1) Exhaust gas residual heat (kiln exhaust gas
thermal loss)
At the start of the 20th century, waste heat power
generation technology using waste heat recovery boilers

105

was developed and spread in use. In Japan, theintroduction of waste heat power generation facilitated
the transition from steam to electricity as the source ofpower for cement plants. This led to improved efficiencyof machinery.
However, as it became easier to purchase electricity
externally, or as more efficient in-house power generation
facilities were developed, cement plants began utilizing
exhaust gas to preheat raw materials directly rather thanfor kiln waste heat power generation, as the maintenanceof the boilers and generators took time and labor.
In the 1930s, the first Lepol kiln was invented inGermany, which had an attached preheater thattransferred heat directly from the exhaust gas to the raw
materials. This was widely adopted in Japan up until the
1960s.
In the 1950s, the suspension preheater (SP) kiln wasdeveloped in Germany, which had even better heatrecovery, made the kiln larger and offered longer
operation. The SP kiln and the Japanese-developed newsuspension preheater (NSP) kiln, with improved thermal
efficiency, long-term operation and upscaling capability,
have been the world’s dominant cement burning devices
ever since.
Meanwhile, in 1907, soon after the emergence of therotary kiln, Asano Cement patented a “calcined lime
burning process” to decarbonize the limestone in advancein a thermally-efficient shaft kiln in order to improve thethermal efficiency of the rotary kiln. The company
adopted the method for its rotary kilns. However, themethod was discontinued in the 1940s as it was difficult
to increase the size of the limekiln. The later developmentof a large-scale limekiln by Onoda Cement, among otherfactors, led to the revival of the calcined lime burning
process in the mid-1950s in the form of the “New
Calcined Lime Burning Process (NCB)”. Production
volumes were successfully quadrupled for a dry-processkiln with a boiler attached. When the SP kiln was
introduced to Japan, Japanese cement companies noted its
superiority and also its limitations for upscaling. Theycame up with the idea of incorporating the advantages of
the NCB into the SP kiln and competed to develop the
New Suspension Preheater (NSP), an SP kiln with
attached precalciner. Several formats were in operation by
the early 1970s. The NSP system had a number ofadvantages, such as saving energy, long-run operation,
reduced NOx emissions and use of alternative feedstock.
It is world-class cement manufacturing technology
developed in Japan.
(2) Clinker residual (sensible) heat (cooler exhaust
heat loss)

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchWhen rotary kilns were first developed, there was norecovery of heat from the clinker coming out of the kiln.
In the 1910s, a “rotary cylinder cooler” was invented,
which allowed heat to be recovered as secondary air for
blowing fuel into the kiln. In the 1920s, a “multi-cylindercooler” was invented in Denmark, which further
improved the heat recovery. These were widely adopted
in Japan for rotary kilns until the 1940s. At around thesame time, a number of device manufacturers in the West
were developing air-quenching coolers (AQC). Whilethese began to be introduced to Japan before the war, they
did not grow widely in popularity until the 1950s, after
the Second World War. Although AQC systems offeredslightly poorer thermal efficiency than the multi-cylinder
system, they gained popularity due to greater ease ofmaintenance and better cement quality. The Fuller system
was adapted for upscaling and was the only cooler systeminstalled from the 1970s onwards. Under the NSP system,
the technology was further developed, with the remaining
cooler exhaust heat in the secondary air utilized as
precalciner combustion air or for drying coal. The
residual cooler heat has been thoroughly utilized.

10.2 Raw Materials Grinding: Technology

Development Goals of Saving Energy
and Producing Raw Materials of Good
Burnability

At the time of the invention of Portland cement to thelate 19th century, when Japan began manufacturing
cement, adequate grinding machinery was not developed
yet. It was very difficult to grind limestone and other hardmaterials finely. Instead, a method was used of calcining
the limestone to form quicklime and then mixing it withwater to form slaked lime powder (the wet process).
In 1891, the tube mill was invented in Germany, which
improved the grinding performance as well as thegrinding efficiency. This was introduced to Japan and by
the end of the 19th century, the grinding of shaft kiln raw
materials had shifted to the dry process.
Up until the 1940s, it was not easy to adjust the powder
fineness nor to achieve good homogeneity of raw
materials by using the tube mill dry process. On the other
hand, in response to consumer demand in the 1930s to
develop concrete technology, cement companies had tobegin producing high quality cement, such as
high-early-strength cement and moderate-heat cement.
They chose to use wet process grinding in order to obtainfinely-ground, well-homogenized raw materials. However,raw materials ground using the wet process required moreheat during the burning process than dry process materials
to evaporate the moisture content. Companies in the Westdeveloped wet process kilns attached with both a boiler
and filters to filter out the moisture content. Also, the long
wet kiln was developed. This elongated kiln used waste
heat for drying raw feed. Japan introduced the former in1932 and the latter in 1954.
In the 1950s, improvements in separators meant
improved adjusting of powder fineness during dry process

grinding of raw materials. The introduction of theblending silo, developed in Germany in the 1960s, further
improved the homogeneity of the raw materials as well.
In the 1970s, technology was developed that incorporated
online X-ray fluorescence analysis and computerized
control of raw mix proportioning. The dry process thensurpassed the wet process in terms of proportioning
accuracy, powder fineness and homogeneity. The wet
process, which required more heat consumption, was nolonger necessary. As the dry process SP kiln rose todominance, the wet process disappeared from cement
plants altogether.
In the 1930s, vertical (roller) mill technology wasdeveloped for grinding raw materials. Since it required
less energy than the tube mill, it began to be widelyadopted around the 1960s, as better structural materials
were developed for the grinding rollers and table. The
vertical mill used kiln exhaust gas to dry the raw
materials at the same time. It was also capable of
upscaling. Combined with the SP kiln, it formed anenergy-efficient integrated process from raw materials toburning.

10.3 Finishing Process: Technology
Development Goals of Saving Energy andProducing High-Quality Cement
Powdered cement in the shaft (bottle) kiln era wasweathered to prevent rapid hardening and to prevent
expansion of the concrete due to free lime. The issue of
rapid hardening was solved by the addition of gypsum,
introduced in 1888. The introduction of the rotary kiln
also reduced the amount of free lime. The weathering
process was discontinued as shaft kilns fell out of use.
At the end of the 19th century, tube mills wereintroduced into the finishing process as well, improving
the grinding efficiency (energy efficiency) as well as
improving the quality of the cement by improving theparticle size distribution. In 1973, the addition of grinding
aids was approved under the JIS, further improving thegrinding efficiency.
As the facilities for the burning process increased insize due to the adoption of SP and NSP systems, thefacilities for the finishing process also increased in size.
This resulted in the development of new Japanesetechnologies and devices, such as eddy current separators,
clinker (finishing) grinding vertical mills and finishingmill pre-crushers. These were exported to the world,
along with the NSP system.

10.4 Shipping Process: Technology
Development Goal of Reducing
Distribution Cost
In the late 19th century and early 20th century, cement
was transported in barrels. Jute sacks were used from the
1910s, followed by paper sacks from the late 1920s. In

History of Cement Manufacturing Technology

106

the 1950s, it became more common for concrete to bemixed at the ready-mixed concrete plant and transported
by mixer truck to construction sites rather than mixing
concrete on site. Accordingly, bulk shipping became thepredominant method of shipping cement from cement
plants to storage silos in markets. The shift to bulk
shipping of cement resulted in a dramatic change incement distribution, or a “distribution revolution”. Thisand the upscaling of cement plants made possible by the
SP and NSP systems were the primary factors enabling
the cement industry’s integration of production inlarge-scale cement plants in coastal areas.

10.5JIS Standards and Cement Diversification
As the first industrial standard in Japan, the Japanese
test method for Portland cement was enacted in 1905.
This kept being revised to reflect advances in technology
and consumer demand. In the 1970s, cement products
diversified through advances in cement chemistry, withcorresponding standards established. In the 1990s, JIS
standards for alkalis and chlorine ion content in cement
were set in order to ensure concrete durability. Also in the
1990s, concrete additives were developed to become themain means of determining concrete performance.
Accordingly, very few further attempts were made to107

produce new types of cement after that.

10.6Evolving to a Core Industry Supporting a
Resource-Recycling Society in the 21
Centuryst

From around the 1970s, the cement industry began touse large volumes of industrial waste and byproducts asalternative fuel and raw materials (AFR). The use ofindustrial waste was initially a means of reducing fuel andraw material costs. From the 1990s, the industry
expanded in scope from recycling industrial waste toincluding general municipal waste. In the 21st century, thecement industry has evolved from a “key industry
providing construction materials” to a “core industry
supporting a sustainable resource-recycling society”.
Throughout this process, Japan has continued to develop
new technologies, such as the chlorine bypass system,ecocement, ash washing and the AK system. Technology
development by cement companies continues to focus on
recycling even more waste as cement feed.
Following the Great East Japan Earthquake of March7DLKHL\R&HPHQW¶VƿIXQDWRSODQWDQGRWKHUFHPHQW
SODQWVLQWKH7ǀKRNXDQG.DQWǀDUHDVPDGHDVLJQLILFDQW
contribution to disaster waste disposal.

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March11 Conclusion and Acknowledgements
In 1899, with the 20th century looming, master inventor
Thomas Edison proclaimed that the 20th century would be
the century of concrete. He began constructing a cement
plant with an output capacity of 1600 tons per day, an
unprecedented volume for the time. Edison’s prediction
was correct: as the provider of the key ingredient for
concrete, the cement industry has indeed made asignificant contribution to society throughout the 20th
century as a key industry providing an essential material
to social infrastructure, including homes, high-risebuildings, roads, railroads, harbors, rivers andwatercourses. The latter half of the 20th century inparticular saw huge advances in cement manufacturing
technology. Systems were created that made it possible toproduce and supply mass volumes of inexpensive yet highquality cement. Cement types became more diverse in
response to demand for greater concrete performance andfunctionality. The supply of this high quality cement inmass volumes, consistent quality and low prices has
indeed undergirded the “concrete civilization” of the 20th
century.
Chapters 1 to 8 of this report discussed the history oftechnology in the cement industry. The Japanese cement
industry originated with the government-managed cement
plant of the late 19th century. Equipment was purchasedfrom the West and the technology was studied anddeveloped. In the 1970s, Japan was producing
ground-breaking new technologies, such as the NSP
system. By the end of the 20th century, Japan had risen toworldwide preeminence in product quality and energy
conservation. Leading-edge Japanese cement
manufacturing technology is now being exported to theentire world. Japanese cement companies have been
expanding overseas (mainly into Asia and the Pacific) inearnest since the 1990s and this technology gives themthe competitive edge.
Meanwhile, the domestic demand for cement in Japan
reached full maturity in the 1990s and unfortunately nofurther quantitative expansion of domestic demand is
expected. Given these severe economic conditions, theJapanese cement industry used its cement manufacturing
technology to advance into a new area of waste recycling,
thus contributing to a sustainable resource-recycling
society and setting itself up for new growth in the 21st
century.
The Japanese cement industry began utilizing waste in
the 1970s. Since the dawn of the cement industry in thelate 19th century, it has been developing manufacturing
facilities and technology, as well as building up a wealthof knowledge in cement chemistry. By actively utilizingthese assets and also developing new technologies, theindustry has pioneered ambitious new areas, allowing it toincrease the variety, quality and volume of waste it canprocess. Chapter 9 discussed the innovations in the
cement industry over the past two decades. The
trailblazing waste recycling technology of the Japanese
cement industry is gaining international attention with thegrowing awareness of global environmental issues.
In order for cement companies to contribute to asustainable resource-recycling society, it is essential thatthey sell cement. There needs to be a cement industry forthere to be waste recycling. Consequently, those in the
cement industry must never forget their time-honored roleof producing the valuable commodity that is cement,
while also taking pride in their position as a core industry
in a sustainable resource-recycling society. Meanwhile,wider society needs to be aware that cement is more thanjust an ingredient in concrete; it is an essential ingredientin the building of a sustainable resource-recycling society.
These closing comments are from the author as a memberof the cement industry for half a century.
Acknowledgements
The Japan Cement Association Research andDevelopment Laboratory and Taiheiyo Cement
Corporation have cooperated fully in the writing of thisreport. The author expresses sincere thanks those below
who took part.
Japan Cement Association Research andDevelopment Laboratory+LGHNL.RQGǀ7RVKLNL1DJDWD
Taiheiyo Cement Corporation
Kenji Ogawa, Keiichi Miura, Takayoshi Okamura,
Mamoru Ishii, Takeshi Katsuki, Kayomi
Yamanishi, Keiko Takahashi, Rie Yoshino
Toshiki Nagata offered assistance collecting materials
and checking document manuscripts related to the cement
industry and the Cement Association. Keiichi Miura and
Takatoshi Okamura organized the collaboration system
for Taiheiyo Cement, while Takatoshi Okamura also
provided valuable knowledge of manuscript contents.
Kayomi Yamanishi offered a lot of support in searchingmaterials in the company’s library and proofreading
manuscripts. Rie Yoshino created and corrected a numberof figures and tables, including the technology
systematization diagram. The author is deeply grateful toyou all.
The author also wishes to express heartfelt thanks to all
the writers of the many papers cited in this report. In
particular, a paper by Dr. Tomikazu Dainobu was widely
cited in Chapter 3 “Cement Manufacturing Technology inJapan in the Meiji and Taisho Periods”. The author
wishes to express his gratitude with this special mention.

History of Cement Manufacturing Technology

108

109
Meiji

TaishoRaw materials
process(shaft kiln)(rotary kiln)(Rotary kiln)

Wet
process

Dryprocess

Dryprocess

Showa

Heisei• Blending silo
• on-line X-ray fluorescence analysis• Computerized control of raw material
proportioning• Vertical mill

Tube mill separator / closed circuit grinding
Wet process
grinding

Kiln

Finishing andshipping
processes(discontinued)(dry process) kiln with boiler
attached

Rotary kiln

• Robotic analysis system

Upscaling(discontinued)
SP kiln

Upscaling

Prevalence of NSP

NSP kiln
Calcined lime
burning process(revived) new calcined lime
burning process(discontinued)• Low waste heat power
generation• Computerized control(wet process) kiln with boiler
attached

Wet process

Government-managed cement plant established• Shaft kiln

Dry process

Burning
process

Prevalence of dry
process

Cooler• Rotary cylinder(discontinued)

Chlorine bypass(discontinued)

Long kiln

Ash washing(discontinued)(semi-dry process) Lepol kiln

Ecocement
AK system• Fuller typeMulti-cylinder

Waste recycling
technology

Fuel• Heavyoil• CoalPowersource• Electricity, electricmotor• Steam engine• Weathering• CoalAdding gypsum

Grinding aids

• Closed circuit
grinding

Tube millVertical millUpscaling• BarrelStandardizationand productdiversification
Waste andbyproduct
recycling

Paper
sack

Jute sackIndustry standards
established• Blast-furnace slag
(blast-furnace slag
cement)Bulk shipping

Bulk distribution system established• Product diversification
White cement, high-early-strength cement,
moderate-heat cement, blended cement• Byproduct gypsum• Greater diversification

Alkali and chlorine content
regulation• Coal ash• Tires, waste plastic, waste oil• Incineration ash, municipal waste, biosolids, otherindustrial waste
Great East Japan
Earthquake disaster
waste processing

Core industry supporting a sustainable resource-recycling society

Western calendar(year)
Japanese calendar(year)

Invention of Portland cement

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March

Systematization Diagram of Cement Manufacturing Technology in Japan(cited from the National Museum of Science and Technology Center of the History of Japanese Industrial Technology database)
No.

Name

Year
manufactured

Manufacturer

1

Shaft kiln of the former Onoda
Cement Company

1883

2

Roller from a fret grinding millc.
1875-18 Unknown
82

3

Steam engine

Taiheiyo Cement
Corporation

Type ofresource

Status ofresource

Structure

Taiheiyo Cement
Open to the
Corporation Onoda OfficepublicSanyo-Onoda, Yamaguchi

As the only complete cement burning shaft kiln in Japan, this kiln is a very
valuable piece of the history of the modern ceramics industry. It has importanceas the central facility of the former Onoda Cement Company, which undergirded
the modernization of the construction industry in Western Japan. Designated as
an important cultural asset in December 2004. See Section 2.3.3.

DeviceAsano ConcreteOpen to the
Corporation
publicKoto, Tokyo

Cement manufacturing equipment from the days of the Ministry of Industry
Fukagawa Works Sub-Bureau, Japan’s first cement plant. The plant was latersold to Asano Cement Company in 1883. See Section 3.2.3.

DeviceTaiheiyo Cement
Open to the
Corporation Onoda OfficepublicSanyo-Onoda, Yamaguchi

A steam engine used to drive the cement manufacturing machinery from when
Onoda Cement, Japan’s first private cement company, started operating. It is theearliest extant steam engine used in a domestic plant. It is the only extant engine
manufactured by the Osaka Army Arsenal for a private plant. See Section 3.5.

Location

Reason for selection

1881

Osaka Army
Arsenal1936

Kiyotada Maru is Japan’s first bulk cement tanker, commissioned in April 1967.
With a total tonnage 3,079 (deadweight tonnage 3,648), this single-helix diesel
Ube Shipping & Logistics,
Model
Open to thevessel had a propulsion of 1,650 hp. Loading was done by a more rational
Heavy Industries,
Ltd.
photographpublicair-blown method rather than a Western-style conveyor system. Combined with
Ube, YamaguchiLtd.
theestablishment of stock points nationwide, this achieved remarkable
Kobe Shipyard
streamlining of transportation. See Section 4.12.3.

1972

Ube Industries,Ltd.

The Isa No. 1 Kiln is a suspension preheater (SP) kiln 6.2m in diameter and
Ube Industries, Ltd.
Open to the Ube Construction Materials 125m in length. Its fire lighting ceremony was held on September 29, 1972. It
Photographpublic Co., Ltd.
has an annual output capacity of 1.86 million tons, the highest in the world at theMine, Yamaguchi
time. It is also the largest existing SP kiln in the world. See Section 5.1.

Ube Industries,
Ltd.

Japan’s first pozzolan cement blended with fly ash emitted from a coal-fired
Ube Industries, Ltd.
Ube Construction Materials power plant was released on the market in February 1987. Compared to ordinary
Open to the Co., Ltd.
Portland cement, pozzolan cement blended with fly ash has greater long-term
Literature
Research & Development strength, better finishing, less free lime, better water resistance, better chemical
publicCenterresistance and less shrinkage. It was later standardized under JIS R 5213 (fly-ash
Ube, Yamaguchi
cement). See Section 8.3.2 (3).

Mitsubishi

History of Cement Manufacturing Technology

4Japan’s first bulk cement tanker,
Kiyotada Maru

5

The world’s largest SP kiln, Isa
No. 1 Kiln

6

Japan’s first fly-ash cement(pozzolan cement)

1956

110

Chronology of Cement Manufacturing Technology
Western
calendarJapanesecalendar

Japan

BC

World

Related major events (Japan, world)7000 BCArchaeological site in Israel containing concrete-likematerial
3000 BCDadiwan archaeological site in China containing
concrete-like material
2600 BCEgyptian pyramids containing inorganic adhesivematerial
1000 BCGreece, volcanic ash mixed with slaked lime
200BCRome, “kiln” built to manufacture quicklime andhemihydrate gypsum
The age of “ancient cement” in Greece, Rome and the Middle Ages 1770s Industrial Revolution in England(technical stagnation)
1776 American War of Independence
1789 French Revolution
1820s Industrial Revolution in Germany

1750
1756

Smeaton (UK)
Invention of “hydraulic mortar” (beginning of modern
cement)1796

Parker (UK)
Invention of Roman cement

1815

John (Germany), 1818 Vicat (France)
Invention of a method of manufacturing “hydraulicmortar” by burning a mix of limestone and clay

1824

Aspdin (UK)Patented “Portland cement”

1830

Fuchs (Germany)“hydraulic properties due to chemical bonding between
silicic acid and lime”

1844

Johnson (UK)
Established the basic principles of Portland cement
manufacturing

1848(France) Portland cement manufacturing begins

1790

1810

1820

1830

1840

1850

1850
(Germany) Portland cement manufacturing begins
mid-1800s(UK) Regulating of setting by weathering

1860
1861

Bunkyu 1

Portland cement first imported (construction of Nagasaki
Ironworks)
1862
1867

Langen (Germany)
Discovery of the latent hydraulic properties of
granulated blast-furnace slag
Monier (France)
Invention of reinforced concrete
1868 Meiji Reformation

1870

Meiji 3

1870

1873

Meiji 6First manufacture and shipping of cement by Fukagawa
government-managed cement plant

1875

Meiji 8

Fukagawa government-managed cement plant starts
manufacturing cement rivalling the quality of imported product

1871

Michaelis (Germany)
Discovery of the delayed setting effect of gypsum
Discovery of the basic principle of blended cement(USA) Portland cement manufacturing begins
1872 Great Fire of Tokyo/Ginza

1877 Satsuma Rebellion
1880

Meiji 131883

Meiji 16

Onoda Cement plant (Yamaguchi) starts operation (privately
managed)Shipping in barrels, net weight per barrel of 400 pounds (181
kg)

1884

Meiji 17

Fukagawa government-managed cement plant sold to 6ǀLFKLUǀ
Asano

1878

(Germany) World’s first cement standard

1882

Le Chatelier (France)
Uses polarization microscopy of clinker thin flakes to
identify the most commonly occurring phase in clinker
as 3CaO·SiO2
Prussing (Germany)
Invention of blast-furnace slag cement

1883(Germany) Addition of gypsum approved

1885

Michaelis (Germany)
Proposal of “hydraulic modulus”
Ransome (UK)Patented the use of rotary kilns for cement burning
Jackson (USA)Published on pre-stressed concrete

1886
1888

Meiji 211890

Meiji 23

Asano starts adding gypsum to regulate setting
Onoda starts manufacturing using the shaft kiln dry process

1893

Meiji 26

8 cement companies request the Minister of Agriculture andCommerce for standardized cement test methods

1895

Meiji 28

Reinforced concrete technology imported

1896

111

1880s (Germany) White cement manufacturing begins
1890s Atlas (USA)
Successful burning of cement in a rotary kiln
1892
Davidsen (Denmark)Invention of the tube mill1892
Michaelis (Germany)
Discovery of hydrate “cement bacillus”

1897

Meiji 30

Onoda changes the net weight per barrel to 380 pounds (172
kg)

1898

Meiji 31

Onoda starts using jute sacks holding 190 pounds (86 kg)“Japanese Imperial Portland Cement Test Methods” proposedby cement industry members

1899

Meiji 32

Asano installs a tube mill (raw materials grinding, Moji plant)

1900

Meiji 33

Japan Portland Cement Association established
Onoda manufactures Japan’s first blended cement

1891 Mino-Owari Earthquake (proof of the earthquake-resistanceof concrete)

1894-95 First Sino-Japanese War
1895 Roentgen (Germany)
Discovery of X-rays
1896

Atlas Cement Company (USA)
Successful burning in a rotary kiln with cooling cylinder
attached

1897

Törnebohm (Sweden)
Naming and heavy media separation of clinker minerals

1900

Polysius (Germany)
Invention of the compound tube millNational Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. MarchWesterncalendarJapanesecalendar

1901

Meiji 34

Cement barrel unified across the industry at 380 pounds (172
kg)

1903

Meiji 36

Asano installs the first rotary kiln in Japan (Fukagawa plant)
The first concrete bridge (Lake Biwa Canal)

1904

Meiji 37

The first reinforced concrete construction (Sasebo)

1905

Meiji 38

The first cement standard created
Ministry of Agriculture and Commerce Notice No. 35 “JapanesePortland Cement Testing Methods”

Japan

World

1907

Meiji 40

Asano patents the calcined lime burning process

1909

Meiji 42

Onoda starts operation at its Dalian plant (the first overseas
plant)

1910

Meiji 43

Asano installs an air separator

1911

Meiji 44

Onoda and Asano’s Moji plant start using electricity as a powersource1912

Taisho 1

Jute sacks start being used instead of barrels

1913

Taisho 2

Yawata Iron Works starts producing “blast-furnace slag
cement”

Related m ajor events (Japan, world)

1901(USA) Construction completed on master inventor
Thomas Edison’s cement plant

1905(UK) Cem ent standard created

1906(USA) Cem ent standard created(USA) Bates packer patented

1906 (USA) Cottrell precipitator patented(successfully used on a working machine at practical use
at a lead smelting works)

1913

Kuhl (Germany)
Proposal of silica modulus and iron modulus
Spindel (Austria)
Successful manufacturing of high-early-strength cement

1913 Bragg father and son (USA)
X-ray analysis of crystal structure

1915

Rankin (USA) & Wright (USA)C-S-A 3-way phase equilibrium diagram completed(USA) Successful implementation of waste heat boiler(using forced draft)
Emley (USA)
Proposal of a method of free lime quantitative analysis(*)(* This method later spread after being improved uponby Lerch (USA) & Bogue (USA) in 1930)

1904-05 Russo-Japanese War

1912 Laue (Germany)
Discovery of X-ray diffraction phenomenon

1914

1914-18 First World War

1915

1916

Taisho 5

Onoda starts manufacturing white cem ent

1917

Taisho 6

Asano installs a Cottrell electrostatic precipitator at its
Fukagawa plant

1920

Taisho 9

Onoda installs a waste heat power generation boiler (Onoda
plant)

1921

Taisho 10

The industry establishes two types of jute sacks, 127 pounds(58 kg) and 95 pounds (43 kg)

1922

Taisho 11

Asano installs a Bates packer

Taisho 13

The industry adopts the metric system and standardizes
shipping weight at 50 kg for sacks and 170 kg for barrels

1923
1924

1920 (Japan) Recession following the First World War
worsens

1923

FL Smith (Denm ark)
Development of a multi-cylinder Unax cooler

1925

Taisho 14

Chichibu uses paper sacks for cement packaging

1925(USA) Continuous slurry filter installed on a wet process
kiln

1926

Taisho 15

Blast-furnace slag cem ent standardized

1926

Hansen (USA) & Bogue (USA)Use of X-ray diffraction to identify clinker minerals

1927

Showa 2Asano adopts a multi-cylinder cooler (Fukagawa plant)

1928

Showa 3Tokuyama installs an air-quenching cooler

1928

Freyssinet (France)
Established the basic principles of pre-stressed
concrete

1929

Showa 4

Asano installs a wet process kiln (Nishitama plant )Asano starts manufacturing high-early-strength cement

1929

Bogue (USA)
Proposal of the Bogue method for calculating clinker
mineral composition

1930(Germany) Invention of the Lepol kiln

1932

Showa 7

Onoda installs a kiln with a wet process filter attached (Fujiwara
plant)

1932(USA) Grinding aid RDA goes on the market(USA) Large volumes of low-heat cement used in dam
construction

1934

Showa 9Mikawa installs a Lepol kiln (Tahara plant, Aichi)
Asano starts manufacturing moderate-heat cement

1934

Polysius (Germany)
Development of the air blending silo
(Germany) First use of a Loesche vertical mill at a
cement plant

1935

Showa 10

A number of companies start manufacturing silica cem ent

1936

Showa 11

Ube commissions bulk cement tanker Kiyotada Maru (3600
tons)
Domestic cement bulk cement shipping

1937

Showa 12

1938

Showa 13

Early-high-strength cem ent standardized

1938

Mussgnug (Germany), Hagerman (Germany)
Publication on the optimum amount of added gypsum

1939

Showa 14Pre-stressed concrete technology introduced

1927 (Japan) Financial crisis

)

1941

Showa 16

1942

Showa 17

1945

Showa 20

1946

Showa 21

Cem ent Technology Association founded

1947

Showa 22

Cem ent exports resum e

1949

Showa 24

The first ready-mixed concrete plant, Iwaki Narihirabashi(Tokyo)Pre-stressed concrete put to practical use

1950

Showa 25

JIS for cement established in place of the JES for ceramics
Cement free trade system resumed

1951

Showa 26

Nihon Cement installs the first Fuller cooler (Nishitama plant)
Ube starts burning with heavy oil
Onoda installs an electron microscope

1953

Showa 28

Moderate-heat cem ent standardized under JIS

1954

Showa 29

Tokuyama installs the first wet process long kiln

1955

Showa 30

<Advances in bulk shipping from around this time>

1956

Showa 31

Ube starts marketing fly-ash cem ent

1957

Showa 32

Aso introduces a blending silo (batch-type)

1959

Showa 34

Onoda starts transitioning to new calcined lime burning process
Onoda introduces a continuous blending silo
Ube installs the first raw material vertical mill (Loesche)

1960

Showa 35

Fly-ash cement standardized under the JIS
Transition to heavy oil advances rapidly from this year
Trial computerized process control begins around this year
EPMA is applied to cement chemistry research from aroundthis time

1929 Worldwide Great Depression

1937 Second Sino-Japanese War

1941 Pacific War
Non-construction cem ent standardized
1945 (Japan) Potsdam Declaration accepted1950

Humboldt (Germany)
Development of the SP kiln

1950 Korean War

1955-56 (Japan) Economic boom

1959Riverside (USA), Ideal (USA) and others
Start of computerized control

1959 (Japan) Economic boom

1961 (Japan) Trade liberalization begins

History of Cement Manufacturing Technology

112WesterncalendarJapanesecalendar

Japan

1962

Showa 37

Chichibu installs computerized control at its Kumagaya plant

1963

Showa 38

Daiichi installs the first SP kiln
Mitsubishi installs the first double rotator mill (Higashitani plant)

World
Wedag (Germany)
Development of cyclone separator

1962 (Japan) Smoke and Soot Regulation Law

1964

CPC (USA)
Trial computerized control of raw materials and burning
processes

1964 (Japan) Tokyo Olympic Games
7ǀNDLGǀ6KLQNDQVHQRSHQV

1965
1966

1965-70 (Japan) Izanagi economic boom
Showa 41

Chichibu adopts the first cyclone separator
The Cement Technology Association is reorganized into the
Research and Development Laboratory
The Ono Method of microscopy mostly complete from aroundthis time

1967

1967

Magotteaux (Belgium)
Development of high Cr wear-resistant balls (allowing asmaller diameter)

1968

Showa 43

5th International Symposium on the Chemistry of Cement heldin Tokyo1968 (Japan) Air Pollution Control Act

1971

Showa 46

Mitsubishi installs the world’s first NSP kiln (Higashitani plant,
Fukuoka)
SF and RSP developed within one year
Cement sacks lightened from 50kg to 40kg

1971 Dollar shock1973

Showa 48

JIS revised to enable the use of grinding aids

1973 Oil crisis

1974

Showa 49

Chichibu/IHI export SF technology to Fuller (USA) (first cement
technology export)

1976

Showa 51

Onoda establishes Onoda Engineering(first engineering subsidiary of a cement company)

1977

Showa 52

Regulation of cement kiln NOx begins
Ube implements a 1-kiln 1-mill system using a Loesche mill

1978

Showa 53

Sulphate-resistant cement standardized under the JIS
Nihon Cement develops technology for feeding waste tires into
kilns

1979

Showa 54

Onoda develops the O-SEPA, the world’s first eddy current
separator
Addition of up to 5% additives permitted by JIS for ordinary
cement1980

Showa 55

<Waste heat power generation starts spreading to the NSP
system around this time><Concrete damage from alkali and chloride content becomes
an issue><Research and development of high belite cement becomes
more active>

1986

Showa 61

Alkali content of cement standardized under the JIS

1987

Showa 62

Chichibu develops the CKP finishing mill pre-grinder

1988

Showa 63

Onoda develops the OK mill, the world’s first vertical cement
grinding mill

1988 -DSDQ &RQVWUXFWLRQRIWKH$NDVKL.DLN\ǀ%ULGJHEHJLQV1990

Heisei 2

Chichibu invents the chlorine bypass system

1990 (Japan) Bubble economy begins to burst
1991 USSR dissolves

1992

Heisei 4

Chlorine ion content of cement standardized under the JIS(0.02%)
Alkali content of all types of Portland cement is regulated to be
0.75% at maximum
Chichibu commercializes high belite cement
Tokuyama develops technology for using waste plastic as kiln
feed

1994

Heisei 6

Onoda and Chichibu merge to form Chichibu Onoda
Sumitomo and Osaka merge to form Sumitomo Osaka Cement

1996

Heisei 8

Domestic cement production of 99.27 million tons (declining
trend after that)
Cement sacks lightened 40kg to 25kg

1998

Heisei 10

Chichibu Onoda merges with Nihon to form Taiheiyo Cement
Ube and Mitsubishi form a joint venture Ube-Mitsubishi Cement
Taiheiyo starts operating the first incinerator ash washingsystem1999

Heisei 11

The WBCSD launches the Cement Sustainability Initiative(CSI) for international cooperation on environmental issues

2001

Heisei 13

Taiheiyo and its partner companies start operating the Ichihara
Ecocement Plant

1995

113

Related major events (Japan, world)

1962

1978

(USA, Germany) Development of high-belite cement
begins around this time1978 Oil crisis

1995 (Japan) Great Hanshin Earthquake

2002

Heisei 14

Taiheiyo starts commercial operation of the AK system

2003

Heisei 15

Chlorine ion content of cement eased to 0.035%

2005

Heisei 17

Taiheiyo changes from a Cottrell to a bag filter at the
Kumagaya plant

2006

Heisei 18

Tokyo Tama Ecocement Facility commences operation2011

Heisei 23

2011 (Japan) Great East Japan Earthquake

National Museum of Nature and Science Survey Report of Systematization of Technology, Vol.23 2016. March