BUILDING RESEARCH INSTITUTE

Where Do
Demolished
Buildings Go?
This month’s installment of our series introducing the varied activities of Japan’s Building ResearchInstitute (BRI) looks at some of the advanced recycling techniques the BRI has under development for
waste construction materials, in particular concrete.

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Figure 1: Production of concrete and the estimatedgeneration of concrete waste
Concrete production volume
Production volume / Volume generated(million tons)

Estimated generated concrete
waste volume

Year

Figure 2: Remaining capacity and remaining years of final
disposal sites
Remaining capacity

Remaining years

Remaining capacity(thousand cubic meters)

Estimated remaining years

Fiscal year30

t is predicted that there will soon
be a large amount of constructionwaste produced in Japan because
the time is coming for when thebuildings constructed during the period of rapid economic growth of the
1960s will be demolished and rebuilt.
In addition, since buildings consist ofa large amount of materials such asconcrete, steel and wood, many resources and much energy are required
for their construction.
Figure 1 shows the production ofready-mixed concrete and the estimated generation of concrete waste.
Concrete production was at 150 million tons in 1960 and grew to nearly
600 million tons in 1973—an averageannual increase of around 30 million
tons. Since then production has beenaround 600 million tons. However, theamount of concrete waste generated
has suddenly started to rise thirty toforty years after the economic growth
period. The amount generated in 2000
was around 100 million tons, but it ispredicted to climb to over 400 million
tons in 2020.
Figure 2 shows the remaining capacity of final disposal sites and theestimated remaining years before theyreach capacity. The capacity of final
disposal sites has been very limited, sothe remaining capacity steadily continues to remain almost unchanged. But
thanks to progress in recycling technology, the remaining life of these sites
has been growing longer. However,when considering the future increase inwaste, even more advanced recycling

techniques will need to be developed.
In addition, since Japan is poor in natural resources, accelerating the use ofrecycled and unused materials becomesa big issue.
The Building Research Instituteis developing and assessing recycling techniques for construction
materials. The following are somerecycling techniques for concrete,
which makes up a large proportionof construction waste.

Figure 3: Typical composition of concrete

Cement Water

Coarse aggregate

Fine aggregate

Composition of Concrete
Figure 3 is the typical composition ofconcrete. Concrete is mainly made up of
cement, water and aggregate (coarseaggregate and fine aggregate), andweighs about 2,300 kg per cubic meter.
This document describes recent topics inrecycling technology for the materials
that make up the greater proportion ofconcrete: cement and aggregate.
Regarding cement, this document
describes the efforts to reduce CO 2emissions and include large amounts
of industrial waste and byproducts incement produced in Japan, as well as thedevelopment of a new cement calledeco-cement.
Regarding aggregate, this document
describes recycled aggregate, which isUnit Weight (kg/m3)

extracted from the aggregate that comesfrom concrete waste generated from thedemolition of concrete structures.

dustry. An unusually large amount oftypes and volumes of industrial waste
and byproducts are used in the production of cement, and those which
Cement and Recycling
include calcium and silica are used as
ingredients and mineral admixtures
Use of industrial waste and byproductsthat make up a few percentage points
The main ingredients in cement are of the ingredients in cement. In addilimestone, clay and iron, however tion, organic materials are mainly
other than those, a large amount of used for thermal energy. The producindustrial waste and byproducts are tion of cement has been declining
also used. Table 1 shows the types and since its peak in 1996 when 99.267
volumes of industrial waste and by- million tons were produced, but inproducts utilized by the cement in- recent years the amount of industrial
waste and byproducts usedin the manufacture of ceTable 1: Volume of industrial waste and byproducts used in cement production
ment has reached almost(FY 2009)
t h e s ame lev el, a n d t h eVolume usedamount used per ton of ce(thousand tons)
ment is increasing.
TypeMain use
Great efforts are also
FY 2003
FY 2006
FY 2009
being made to reduce CO 2
Blast furnace slag
Raw materials, mineral admixtures
10,1739,7117,647
emissions from the manufacture of cement in Japan.
Coal ash
Raw materials, mineral admixtures
6,429
6,995
6,789
Through developments inSludge
Raw materials
2,413
2,965
2,621
the optimization of heating processes and use of
Soil generated by
Raw materials
629
2,589
2,194
waste heat, the consumpconstruction
tion rate of kiln fuel in theByproduct gypsum
Raw materials (additives)
2,530
2,787
2,090
manufacture of cement has
been declining year by
OthersUsed mainly as raw materials
2,382
2,594
1,798
year, and has been held atUsed mainly for thermal energy
2,632
2,633
2,633
a very low level even incomparison with foreign
Other378
615
518
countries ( figure 4).
Total
27,56430,89026,291
Even now cement is a
textbook example of a
Volume used per ton of cement (kg/t)
375
423
451
material for a recyclingSource: Japan Cement Association
oriented society.
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BUILDING RESEARCH INSTITUTE
Figure 4: Consumption rate of kiln fuel during cement manufacture

BUILDING RESEARCH INSTITUTE

Consumption of kiln fuel(MJ/ton)Twelve European countries: Austria, Belgium,Denmark, Finland, France, Germany, Greece,
Luxembourg, Netherlands, Spain, England, Italy

United States
China

India
Twelve European countries

disposal sites.
However, unlike typical cement, since there is little longterm strength development (figure6), there is a strength deficiency
in the long-term strength development of the compressive strengththat has been expected until now.
Also, because it includes a comparatively large amount of chloride ion, there is a high probability
for the corrosion of rebar encasedin concrete, so caution is requiredin the way that it is used. TheBuilding Research Institute has
conducted many experiments regarding the properties of fresh
concrete, strength and durabilityof concrete made from ecocement, and has developed guidelines for mix design and construction techniques when using ecocement in building construction.

Fiscal Year

Aggregates and Recycling

Source: Japan Cement Association

Figure 5: Eco-concrete manufacturing process

DeliveryPre-processing/Drying, crushing,pulverizing

Firing/Breakdownof dioxins at 1,350°C
and higher

Processing of emissions

Emissions

Development of Eco-Cement
The term eco-cement combines thewords ecology and cement. The reason
that eco-cement is considered an ecological material is that around half ofthe material used for the cement during
the manufacturing process is waste incinerated ash and sewage sludge (figure5). In Japan, trash is first incinerated,
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Finishing/
Pulverizing

Heavy metal extraction facility

Wastewater

Extraction of heavy metal

and then once its volume is reduced, it
is disposed of. But as mentioned earlier,
it is becoming difficult to insure that
there will waste disposal sites for it.
For these reasons eco-cement is considered an ecological material from thedual perspectives of contributing to theconservation of limestone resources aswell as to the conservation of waste

Eco-cement

Waste incinerated ash andsewage sludge

Extraction of steel and aluminum

As shown in figure 3 , a large
amount of aggregate is used inconcrete. However, since there
is a limit to natural high-quality
aggregate, maintaining a continuous supply of it has become
an important issue. The technology for appropriately handling the large amounts of concrete waste generated in thefuture is also necessary. Taking
these things into consideration,technology has been developed
for recycled aggregate extracted
from aggregate from concrete
waste generated from the demolition of concrete structures inJapan. Photo 1 is an example ofrecycled aggregate, and photo 2
is an example of a recycled aggregate manufacturing plant.
Recycled aggregate is relatively low quality when compared to natural aggregate, and muchmoney and energy is required tomanufacture high quality aggregate.
Therefore, as for the manufacture ofrecycled aggregate, of course it will
be manufactured at a high quality, but
it is also important to maintain aquality that is appropriate for the useof the aggregate. The Building

Figure 6: Strength of eco-cement
EC: Eco-Cement
OPC: Ordinary Portland Cement
W/C: Water Cement Ratio

Compressive Strength(N/mm2)

Research Institute has developed quality standards forrecycled aggregate based on its use, and has studied
the methods for mix design for appropriate use. Basedon these research results, three quality standards for
aggregates have been established as part of Japan
Industrial Standards (JIS): Recycled aggregate class H,
recycled aggregate class M and recycled aggregateclass L (table 2).
The technology for recycling construction materials
is indispensable for creating a sustainable society.
Technological development is making progress inJapan, and the recycling of materials as well as the useof recycled material is increasing. In comparison to virgin materials, however, they are lacking in performance,
so it has become an issue of using the proper materials
in the proper place. The Building Research Institute willcontinue to define quality standards and assessment
methods for recycled materials, and make strides in
R&D to provide methods for their appropriate use thatmeets each purpose.

Curing Time (day)Photo 1: Recycled aggregate

Photo 2: Recycled aggregate
manufacturing plant

Table 2: Main uses and quality standards of recycled aggregate
Aggregate type

Crushed aggregate

Recycled aggregateclass H

Recycled aggregateclass M

Recycled aggregateclass LStandard

JIS A 5021

JIS A 5022
Annex AJIS A 5023
Annex A

Main use

All buildings and publicworks (equivalent tonatural aggregate)

Buildings and public works Roadbed material, backfill (for All buildings and public(only foundations and other filling) concrete, concrete for works
areas that are not affected levelingby drying shrinkage orfreeze-thaw)

Dry density (g/cm3)

2.5 and greater

2.3 and greater-

2.5 and greater

Water absorption
ratio (%)

3.0 and lower

5.0 and lower

7.0 and lower

3.0 and lower(Naturalaggregate)(Natural aggregate)
JIS A 5005

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