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«• jr NBS SPECIAL PUBLICATION 542

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

Possible Contributions

of Cement and Concrete

Technology to Energy

Conservation

IbO
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The

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The National Bureau of Standards was reorganized, effective April 9, 1978.
Possible Contributions of

Cement and Concrete Technology

to Energy Conservation

Summary of the NBS/DOE Workshop held

October 3-4, 1977 at the National

Bureau of Standards, Gaithersburg, MD

Edited by:

Geoffrey Frohnsdorff

Paul W. Brown

James R. Clifton

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

Prepared for:

U.S. Department of Energy

20 Massachusetts Avenue, NW

Washington, DC 20234

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued May 1979
Library of Congress Catalog Card Number 78-600056

National Bureau of Standards Special Publication 542

Nat. Bur. Stand. (U.S.), Spec. Publ. 542, 76 pages (May 1979)

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For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402- Price $2.50

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ABSTRACT

A workshop on Possible Contributions of Cement and Concrete Technology to Energy Conservation by the Year 2000 was held at the National

Bureau of Standards on October 3 and 4, 1977. The purpose of the workshop was to identify and record ideas on possible contributions of

cement and concrete technology to energy conservation in the near term

and by the Year 2000. This included consideration of current technology

as well as areas in which technological advances might be realized.

The workshop was divided into working groups on cement composition,

cement production, blending materials, concrete production, efficient

use of concrete, and institutional factors. The essential results from

the six working groups were statements of Energy-Saving Opportunities,

Research Needs, and Unresolved Issues. The statements, which are the

major part of this report, are presented without critical analysis.

They suggest, however, that there are a large number of possible

opportunities which should be evaluated for their ability to contribute

to energy conservation in the cement and concrete industries.

Key Words: Cement; concrete; research needs; energy-saving

opportunities
EDITORS' NOTE

With the exception of Chapters 1 and 8 and the introductory sections of the other chapters, the views expressed are those of the workshop participants. They are edited versions of the written statements

prepared by the working groups and their chairmen and they are presented

without critical analysis. We hope our efforts to express them in a

reasonably uniform style have not in any way changed or obscured the

meanings of the statements.

iv
Table of Contents

Page

ABSTRACT iii

1. INTRODUCTION 1

1.1 Background 1

1.2 Objective and Scope of the Workshop 1

2. CEMENT COMPOSITION 3

2.1 Background 3

2.2 List of Statements Prepared by the Working Group . 3

2.3 Summary of the Discussions 4

2.4 Energy-Saving Opportunities 5

2.5 Research Needs 6

3. CEMENT PRODUCTION 9

3.1 Background 9

3.2 List of Statements Prepared by the Working Group . 9

3.3 Summary of the Discussions 11

3.4 Energy-Saving Opportunities 12

3.5 Research Needs 16

3.6 Unresolved Issue 23

4. BLENDING MATERIALS 24

4.1 Background 24

4.2 List of Statements Prepared by the Working Group . 24

4.3 Summary of the Discussions 25

4.4 Energy-Saving Opportunities 25

4.5 Research Needs 26

v
Page

5. CONCRETE PRODUCTION 29

5.1 Background 29

5.2 List of Statements Prepared by the Working Group 29

5.3 Summary of the Discussions 30

5.4 Energy-Saving Opportunities .... 31

5.5 Research Needs 37

5.6 Unresolved Issue 39

6. EFFICIENT USE OF CONCRETE 41

6.1 Background 41

6.2 List of Statements Prepared by the Working Group 41

6.3 Summary of the Discussions 42

6.4 Energy-Saving Opportunities ... 43

6.5 Research Needs 49

7. INSTITUTIONAL FACTORS 52

7.1 Background 52

7.2 List of Statements Prepared by the Working Group 52

7.3 Summary of the Discussions 53

7.4 Energy-Saving Opportunities 57

7.5 Research Needs 59

7.6 Unresolved Issues . 62

8. SUMMARY 62

9 . ACKNOWLEDGMENTS 65

Appendix I Workshop Steering Committee and Working Group

Chairmen 66

Appendix II Lists of Participants and Working Group Members. . . 67

vi
1. INTRODUCTION

1.1 Background

Concrete is the most widely used material of construction in the

U.S. with more than 500 million tons being placed each year. The

primary constituents of concrete are cement, sand, aggregate, and water

with steel reinforcement being used in many structural applications.

In addition, chemical admixtures are often used to modify characteristics of concrete such as rheological properties, air content and

setting times.

More than 95% of the concrete placed in the U.S. contains portland

cement as the main cementing material. In terms of the energy required

to produce concrete, the manufacture of portland cement uses the largest

amount. In 1975, the U.S. cement industry produced approximately 70 x 10^ tons of portland cement and consumed about 2% of the energy used

in the nation's industrial processes or about 6 x 10 joules.*

Energy conservation in cement manufacture cannot properly be consid

ered independently of the concrete industry which ultimately determines

the efficiency with which the cement is used. Because of the interrelationships between the cement and concrete industries, and the desirability of being able to consider energy conserving options of both

industries simultaneously, the Department of Energy and the National

Bureau of Standards sponsored a two day workshop on the Possible Contributions of Cement and Concrete Technology to Energy Conservation by the

Year 2000. The workshop was held at the National Bureau of Standards

on October 3 and 4, 1977. A special effort was made to obtain the participation of well-informed persons representing a wide range of viewpoints and interests. The total number of participants was 95 with 12

being from foreign countries. As a precondition for participation, each

had been required to submit in advance written ideas for discussion.

The membership of the workshop steering committee is given in Appendix

I and the list of participants in Appendix II.

1.2 Objective and Scope of the Workshop

As its name indicates, the objective of the workshop was to identify opportunties for energy conservation in the manufacture and use of

cement and concrete in the near future and by the Year 2000. The workshop scope included modifications of cements and cement manufacturing

processes, the replacement of a portion of the cement in concrete by

waste or byproduct materials, and the more efficient production and

J.R. Clifton, P.W. Brown, and G. Frohnsdorff, Energy Conservation

Through the Facilitation of Increased Blended Cement Use, NBSIR

76-1008, National Bureau of Standards, Feb. 1976.

1
use of concrete. An equally important part of the scope concerned

institutional factors which might affect the use of energy-conserving

technologies by the producers and users of cement and concrete. To

promote discussion in these areas and bring out as many ideas as

possible, six working groups were established within the workshop under

the headings:

Cement Composition

Cement Production

° Blending Materials

° Concrete Production

Efficient Use of Concrete

0 Institutional Factors

The working groups were of roughly equal size and, as far as possible, assignments to them were based on the interests and expertise

of the participants and the desire to have a broad range of viewpoints

represented in each group. The working group chairmen (See Appendix I)

had been selected in advance and they had been asked to work with

their groups to discuss and prepare statements on the possibilities

for energy conservation in their assigned areas. Between them, the

working groups prepared 59 statements on energy-saving opportunities,

and 67 on research needs; they also drew attention to 4 unresolved

issues. Energy-Saving Opportunities referred to steps which the

respective groups felt could be taken in the near term using current

technology, while Research Needs related to further research which

would have to be carried out if potential energy-saving opportunities

were to be confirmed and exploited. Unresolved Issues indicated areas

where it was felt, at least by some, that there might be opportunities

for energy conservation though there was not now sufficient information

to assess the potential.

This report includes six chapters detailing the outputs of the

six working groups, and a final chapter giving a summary of ideas put

forward by the working groups. It should be noted that the working

groups were requested not to rank the ideas in order of importance.

In view of the limited time available, it was decided it would be

better to try to record all ideas and leave critical analysis and

ranking for another activity.

We hope this report will stimulate energy-conservative actions and

encourage the formulation of still other ideas for energy conservation

in the cement and concrete industries.

2
2. CEMENT COMPOSITION

2.1 Background

Four main types of portland cement are currently produced in the

U.S. Each of these cement types is composed of four primary compounds

which approximate to the compositions: C^S , C2S, C2A, and C^AF, where

C = CaO, S = Si0 2

, A = AI2O3, and F = Fe

2 03

. The relative amounts of

these compounds can, to some extent, be controlled by the manufacturer.

This is done to meet specification requirements and to adjust performance. The four main cement types and their uses and special features

may be summarized as follows:

ASTM Cement Use or Special Characteristics Salient Feature

Type of Specification

I General purpose construction least restrictive

spec

.

II Moderate heat of hydration or

moderate sulfate resistance 8% C3A

III High early strength 1-day strength

1800 psi (12.4MPa)

3-day strength

2. 3500 psi (24.1MPa)

V High sulfate resistance 5% C3A

2.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

a) Standard reference materials

b) High free lime clinker

c) Better matching of cement properties to use

d) Combined production of cement and other products

Research Needs:

a) Optimization of properties of blended cements

b) Nucleating agents for cement hydration

c) Low-lime clinkers and cement
d) Low-temperature processes for production of hydraulicallyactive dicalcium silicates

e) Hydrothermal pretreatments for activation of silicious materials

f) Lime-pozzolan mixtures as replacements for concrete

g) Autoclaved calcium silicate materials

h) Spurrite as a cementing material in autoclave processes

i) Cements containing large quantities of calcium sulfate

j) Cements for use with glass fiber reinforcement

2.3 Summary of the Discussions

The working group on cement composition considered how possible

changes in cement composition could contribute to savings in energy and

materials. Because the calcination of limestone consumes much of the

energy used in portland cement manufacture, several suggestions were concerned with reduction of the lime content of cements; this could be

done either by manufacture of portland cements of lower lime content

or of blended cements containing significant amounts of other inorganic

materials as partial replacements for ground portland cement clinker.

Another group of suggestions recommended the use of silicious cements

which, because they would not contain portland clinker, would require

less energy to manufacture, though more to cure. The more efficient use

of cements by better matching of properties to end use or by enhancement

of performance through the use of nucleating agents was also considered.

Because a reliable analysis of raw materials and products is necessary

for close control of the cement manufacturing process, attention was

drawn to the potential benefits of providing standard reference materials. The adjustment of cement compositions to minimize corrosion of

other constituents of concrete (e.g., steel reinforcing bars and glass

fibers) was considered worthy of research.

In reviewing the discussions, the working group chairman pointed out

the desirability of learning how to increase the grindability of clinkers

and of how to make satisfactory portland cements containing larger

amounts of MgO or calcium sulfate than are presently accepted. He

emphasized the importance of understanding the interactions between

the ingredients of blended cements so that their performance could be

optimized. He also said that, though no specific suggestions were

made, the group had discussed possible uses of waste kiln dusts as

cementing materials, neutralizing agents, fertilizers and replacements

for gypsum in portland cement, and the collection of nitrogen compounds

from kiln gases for possible use in fertilizers. Altogether, the working

group prepared 4 statements of energy-saving opportunities and 10 statements of research needs.

4
Energy-Saving Opportunities

a) Standard Reference Materials

Variations in clinker composition due to variations in kiln

feed cause increased use of energy in clinker production.

Improved control of the composition of kiln feed has been

assisted by the development of rapid analytical techniques, such

as x-ray emission, but the use of these techniques could be

simplified and extended if a larger range of standard reference

materials could be made available. Standard reference materials

are needed for shales, limestones, cement raw mixes, coals, and

coal ash.

b) High Free Lime Clinker

Portland cement clinker is usually required to have a low

free lime content. This helps insure satisfactory performance,

but often at an increased energy cost. A recent patent issued

in the Soviet. Union suggests that energy savings of about 10%

can be obtained in manufacture of clinker by making high free

lime clinkers at temperatures not exceeding 1380°C. The benefits claimed are reduced fuel use in clinker formation,

increased life of kiln linings, improved performance of blended

cements made with the clinker, and easier grinding. This

appears to offer an energy-saving opportunity provided the performance is satisfactory and appropriate standards are available o

c) Better Matching of Cement Properties to Use

The limited number of varieties of cement available hinders the matching of cement properties to user needs. This

may lead to overdesign of concrete mixes with the use of unnecessarily large amounts of cement. More efficient use of materials could be obtained through the mixing of cements with blending materials such as certain types of slags, organic admixtures

and reinforcing materials.

d) Combined Production of Portland Cement and Other Products

Portland clinker is usually manufactured as the sole product of the manufacturing plant. However, depending on the raw

materials available, it is sometimes possible to manufacture

Portland clinker simultaneously with one or more of the following materials: alumina, sulfuric acid, phosphate fertilizers,

and potash. Investigations should be carried out to determine

whether processes involving the combined production of portland

clinker and other products are energy-conserving.
2.5 Research Needs

a) Optimization of Properties of Blended Cements

For any specific blending material (e.g., granulated blastfurnace slag, fly ash, natural pozzolan) it is assumed there is

an optimum portland clinker for use in making a blended cement.

This might not necessarily be the best clinker for making a portland cement. There is a need for research on the effects

of clinker composition and other factors on the performance of

blended cements. If our resources are to be used most effectively, the effects that the phase compositions and particle

size distributions of the clinker and the blended materials have

on the performance of blended cements must be determined.

b) Nucleating Agents for Cement Hydration

It has been observed that the addition of certain hydrated

calcium silicates, such as afwillite, to a paste of the cement

compound alite, accelerate the hydration of the alite and the

hardening of the paste. Further, the hardened paste shows only

about half the drying shrinkage of the hardened paste without

added afwillite. It has also been observed that the addition

of ettringite can accelerate the hardening of a portland cement

paste and increase its rate of strength gain. These effects are

not well understood but it is assumed that the added materials

act as nucleating agents for the hydration products of the

cementing material. If advantage is to be taken of such phenomena in improving the performance of cements, the feasibility

of accelerating cement hydration by means of nucleating agents

should be investigated. Efficient use of all potential cementitious binders will only be realized when there is a fundamental

understanding of the factors causing strength gain, when the

reactivity can be measured and controlled, and when the optimum

microstructure can be produced from each cementing material for

the application in which it is to be used.

c ) Low-Lime Clinkers and Cements

Preliminary research has indicated that cements containing

larger quantities of alumina and SO3 than portland cements can

be made. They contain less lime than portland cements and,

using S to represent SO3, the phases present may include C4A3S

but not C2S. Cements of this type should be compared with portland cements from the points of view of performance and energy

requirements for manufacture and use. There is a need to know

whether the cements make durable concretes and whether they can

be made from sulfur-containing industrial wastes.

6
d) Low-Temperature Processes for Production of HydraulicallyActive Dicalcium Silicates

g-Dicalcium silicate is one of the major cementing compounds in portland cements. However, it reacts much more slowly

than tricalcium silicate. Recent research has shown that much

more reactive g-dicalcium silicate can be made by spray-drying

of gels at about 900°C. This suggests that a dicalcium silicate

cement requiring little or no grinding might be made at a much

lower temperature than portland cement. This possibility should

be investigated.

e ) Hydrothermal Pretreatments for Activation of Silicious Materials

It is suggested that the reactivity of siliceous materials,

such as quartz, granulated slags, and fly ashes, might be

improved through a pretreatment with high pressure steam or with

alkali prior to their use as constituents in blended cements.

f ) Lime-Pozzolan Mixtures as Replacements for Concrete

It is suggested that, for some purposes, lime-pozzolan

mixtures could replace portland cement concrete. Improved

understanding of the reactions between lime and pozzolans and

new ways of controlling them should be sought. This research

should include studies of the effects of low-pressure steam

curing on lime-pozzolan mixtures.

g) Autoclaved Calcium Silicate Materials

In some European countries autoclaved calcium silicate

materials are used on a scale comparable with portland cement

concrete. The products include dense materials such as sandlime block, and less dense ones such as aerated concrete. In

some cases they are reinforced. It may be important that autoclaved calcium silicate products can be made using waste materials such as fly ashes, slags, mining wastes, and other industrial by-products. It is recommended that the potential energy

saving from making autoclaved calcium silicate materials in

the U.S. be evaluated. This would require the total energy

requirements for manufacture of autoclaved calcium silicates

and portland cement concretes to be compared taking into

account all steps from the production of the raw materials

to the completion of construction.

7
h) Spurrite as a Cementing Material in Autoclave Processes

Spurrite is a calcium silicate carbonate which might be a useful cement for use in autoclave processes. Since its manufacture would probably require less enegy than the manufacture

of lime or portland cement, it should be determined whether

spurrite is indeed viable as a cement for autoclaving uses and

whether it can be economically produced both in terms of cost

and energy use.

i ) Cements Containing Large Quantities of Calcium Sulfate

Calcium sulfate dihydrate (gypsum) is an abundant naturally

occurring mineral and also a common process waste. If a substantial fraction of the portland cement used in a variety

of applications could be replaced by some form of calcium

sulfate*, this would almost certainly save energy and help in

the disposal of waste sulfates. Substantial quantities of

calcium sulfate are used in supersulfated cements, but use of

similar quantities in portland cements may lead to the disruptive expansion of concrete. If the factors causing expansion

were understood, they might be controlled so that greater quantities of calcium sulfate could be used. There is, therefore,

a need to carry out research on the factors which cause expansion in cements containing substantial quantities of any of the

forms of calcium sulfate.

j ) Cements for Use with Glass Fiber Reinforcement

There is considerable interest in the use of glass and other

fibers for increasing the tensile strength of mortars and

concrete. Although alkali-resistant glasses are available,

there is still uncertainty about their long-term durabilities

when used in portland cement concrete. Research is needed to

aid the design of cement-fiber systems that are economical and

durable. Research on such systems would have energy-saving > potential because panels of fiber-reinforced materials could

replace thicker panels of concrete or panels of metal such as

aluminum or steel.

* The main forms are anhydrite (CaSO^), hemihydrate (CaSO^'1/2 H

2 0), and

dihydrate (CaS04 *2H2 0)

8
3. CEMENT PRODUCTION

3.1 Background

The manufacture of Portland cement is comprised of three major processing stages for which the approximate average energy requirements

are: * Approximate Approximate Frac

Energy Requirement tion (%) of Total

Process Btu/ton joules /Kg Energy Requirement

Raw materials processing 1.0 x 10 6 1.0 x 10 6 13

Pyroprocessing 5.9 x 10 6 6.1 x 10 6 80

Finish grinding 0.5 x 10 6 0.5 x 10 6

7

Total 7.4 x 106 7.6 x 106 100

Raw materials processing includes quarrying, crushing, drying and grinding. Pyroprocessing shows the largest energy requirement largely because

of the energy required for the calcination of the lime-bearing materials.

In the finish grinding step, the cement clinker, along with the appropriate gypsum addition, is ground to cement fineness. The tabulated figures

are averages for the whole industry. In general, the dry process for

cement manufacture, in which the raw materials are kept dry while being

prepared for pyroprocessing, uses less energy in the first two stages,

while the wet process, in which the raw materials are ground and blended

as slurries, uses more.

3.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

a) Use of finely-divided raw materials

b) Metallurgical slags as raw materials

c) Simultaneous drying and grinding of raw materials

d) Dewatering of raw material slurries by filtration

e) Use of classifying mill liners and flow-controlling diaphragms

to improve mill efficiency

* Energy Conservation Potential in the Cement Industry , Conservation

Paper No. 26. FEA, June 1975; NTIS No. PB-245.159

9
f) Substitution of combustible wastes for traditional fuels

g) Fuels derived from municipal and industrial wastes

h) Use of low grade fuels as partial replacements for high

grade fuels

i) Use of mineralizers to lower the temperature of clinker formation

j) Improved methods for control of the clinkering process

k) New or modified pyroprocessing systems

1) Use of lower-grade heat

m) Cogeneration of electricity and/or steam with clinker

Research Needs:

a) Coal refuse as a cement raw material

b) Flue gas desulfurization wastes as cement raw materials

c) Sewage treatment waste as a cement raw material

d) Production of portland cement from high surface area lime

e) Separate grinding of raw materials

f) Dispersion of raw materials and clinker during grinding

g) Thermal comminution of limestone and other raw materials

h) Alternative methods of comminution

i) Electrical heating of kilns

j) Clinker as a by-product of coal-fired power plants

k) Low-temperature processes for cement production

1) Modeling of clinker production

m) Phase diagrams for portland cement compositions with

mineralizers in kiln atmospheres

n) Measurement and control of clinkering by microscopic analysis

o) Improvement of clinker grindability by control of cooling

history

10
Removal of undesirable volatile components from cement kilns

by increasing exhaust temperatures

q; Reduction of dust generation in clinker manufacturing processes

r) High temperature dust collectors

Dust recycling and waste heat recovery

Effect of clinker structure on grinding energy requirements

Alternative to electrical energy for driving grinding mills

Improvement in efficiency of particle size classification

Cogeneration of electricity and clinker

x; Reduction of power requirements for cement production

Unresolved Issue:

a) Feasibility of complete recycling of dust when using high

sulfur coal as fuel

3.3 Summary of the Discussions

The working group on cement production considered how cement manufacturing operations might be controlled or changed to bring about

savings in energy and materials. It was suggested that certain

finely-divided, or other highly-reactive, raw materials had potential for

reducing the energy required in clinkering and that energy savings in

raw materials preparation could be achieved through changes in methods

of dewatering and drying raw materials. Suggestions were made as to how

the amount of electrical energy used in grinding raw materials and clinker could be reduced and possibilities for use of lower-grade fuels were

mentioned. The importance of controlling the cement kiln to obtain

easily-ground clinker showing optimum performance in cement was touched

on, and the possibility of using fluxes in the raw materials to lower

the kiln burning zone temperature was noted. Improved heat recovery from

kiln exit gases, which could be assisted if high temperature dust collectors could be made available, was seen to offer opportunities for

further energy conservation. A related topic was the possibility of

cogeneration of steam and electricity with clinker. It appeared there

was still some need for new information on phase relationships in oxide

systems relevant to cement manufacture, and the potential benefits of

continuing development of mathematical models representing the kiln

operation were noted. The group documented 13 energy-saving opportunities, 24 research needs, and an unresolved issue relating to the feasibility of complete recycling of kiln dust when high sulfur coal is used

as the fuel.

11
3.4 Energy-Saving Opportunities

a) Use of Finely-Divided Raw Materials

Certain materials with potential for use in cement manufacture normally occur in a finely-divided condition. Examples

are fly ash, aragonite, some silicates, and some forms of silica

and alumina. The complete or partial substitution of these for

more commonly used raw materials could lead to a reduction in

the energy used in the grinding of raw materials.

b) Metallurgical Slags as Raw Materials

There are a number of metallurgical slags which have potential for use as cement-making raw materials. These include

phosphate slags, iron blastfurnace slags, steel slags, foundry

slags, and slags from nonferrous smelters. Although constraints

to the use of some of these slags may be posed by their chemical

compositions, variability, continuity of supply, and transportation and purchase costs, the fact that they have already

undergone heat treatment means they would require less energy

for conversion into clinker. It was recommended that information be published on all slag sources giving the slag chemistry and location in respect to cement plants. Computer programs should be developed to determine whether a particular slag

could be used in combination with a cement plant's raw materials

to give suitable cement compositions.

c) Simultaneous Drying and Grinding of Raw Materials

Using waste heat or supplementary heaters, grinding mills

now available can simultaneously grind and dry materials initially containing up to about 20% of water. Such mills could save

as much as 15% of the heat used in wet process cement manufacture. It is believed such mills could be installed (retrofitted) in most wet cement plants.

d) Dewatering of Raw Material Slurries by Filtration

Certain raw materials, such as chalks and clays, can only

be used in the wet process. It is suggested that the slurries

produced in grinding these materials should be dewatered by filtration to produce the driest practicable filtercake for feed

to the kiln. It is predicted that about 20% of the energy normally required in the wet process could be saved through the

use of filtration. (It should be noted that the separate grinding of alkali-containing materials and filtering them separately

presents an opportunity for removing water-soluble alkalis with

the filtrate water). The major restraints to installation of

filtration equipment are likely to be space and availability

of capital. Good maintenance of filters would be necessary for

avoidance of problems.

12
e) Use of Classifying Mill Liners and Flow-Controlling Diaphragms

to Improve Mill Efficiency

It appears that the efficiency of grinding mills can be

increased through the installation and use of classifying mill

liners and flow-controlling diaphragms. Increases in efficiency

of up to 15% are claimed by manufacturers. Although several

such systems have been installed in the U.S., documentation by

impartial observers has not been made. It would be valuable

in helping cement companies recognize the energy-saving potential of systems of this type, if the claims of the manufacturers

could be verified.

f ) Substitution of Combustible Wastes for Traditional Fuels

Several types of waste materials not currently used as

fuels have potential for replacing the traditional fuels used

in cement manufacture. Examples are waste crank-case oil, waste

solvents, waste cellulosics, and by-product hydrogen. While

there may be logistical and environmental difficulties in making

the fuels available for cement manufacture, and while, particularly in the case of hydrogen, the flame characteristics may

not be the optimum for heat exchange, it is recommended that

the use of these waste materials as fuels be investigated.

g) Fuels Derived from Municipal and Industrial Wastes

There are a large number of possibilities for the production of fuels from municipal and industrial wastes. The

fuels could be in solid, liquid or gaseous form. Although few

of the production processes are commercially proven, several

pilot plants are in operation. It is recommended that consideration be given to the possibilities for using these fuels for

full or partial replacement of the traditional fuels used in

cement manufacture.

h) Use of Low-Grade Fuels as Partial Replacements for HigherGrade Fuels

Lower-grade fuels such as water gas, lignite, and petroleum coke, have a potential for at least partial replacement

of higher-grade fuels for use in cement manufacture. Lignite

and petroleum coke could be supplied to any cement plant and

a water gas plant could be constructed on site with facilities

for removing S02 and/or H 2 S from the gas. The possibilities of

using such fuels in cement manufacture should be investigated.

Among the possible constraints are the availability of the fuel,

the amount of air needed for proper combustion, and the low

heat value of water gas. It is possible that, particularly in

the case of water gas, new burning techniques such as oxygen

enrichment would be needed.

13
Use of Mineralizers to Lower the Temperature of Clinker Formation

It is well known that there are mineralizers which lower

the temperature of clinker formation. Examples are fluorides,

magnesium compounds, and sulfate-containing compounds. Unfortunately, there is a lack of documentation on full and pilot

scale tests to determine the energy savings per ton of clinker,

the effects of mineralizers on kiln linings, the effects of mineralizers on the operation of suspension preheaters and various

types of kilns and, most important, on cement performance. In

view of the possibility of conserving energy through the use

of coarser kiln feeds and shorter burning times, the use of

waste materials containing fluorides and sulfates as mineralizers should be explored. These wastes include fluorosilicates, by-product gypsum, and sulfate scrubber sludges.

Improved Methods for Control of the Clinkering Process

Energy is wasted in the manufacture of portland cement

clinker through irregularities in the operation of cement kilns.

The use of improved methods of kiln control, therefore, has

potential for energy savings. Although equipment suppliers

should have an economic motivation to do research in this area

and publicize the results, information on the technological

advances occurring in the world does not seem to be adequately

disseminated. Few cement manufacturing companies can spare the

staff for the world-wide travel needed. There are two recent

examples of the value of technology-gathering trips. These are

the Kaiser Engineers trip around the world to study precalcining

kilns in at least 24 plants and the European tour conducted

by the PCA after the recent VDZ Congress in Germany. It is

recommended that this type of activity be encouraged with the

PCA being a possible focus.

New or Modified Pyroprocessing Systems

There appear to be several new or modified pyroprocessing

systems which could result in reduced energy consumption in the

manufacture of clinker. Examples are the fluidized bed process,

the air slide kiln for calcining, the oscillating plate kiln

for calcining and clinkering, the use of residual fuels in conventional kilns, and the use of a shaft kiln to preheat pellets

before clinkering in a rotary kiln. Unfortunately, there are

several constraints which hinder the full scale evaluation of

new systems. They include the reluctance of the cement industry

to accept the technical risk of using a virtually untried system

its reluctance to deal with small firms which may not be able

to provide the long-term support needed, and the lack of capital

in the industry. There is, therefore, a need for technical

evaluation and demonstration of these systems in regard to

14
energy use, first cost and operating costs, environmental factors, and process limitations. Between them, the new or modified systems have potential for processing of kiln dust, the

cogeneration of power and clinker, the use of waste-derived

fuels or other low-grade fuels, the replacement of existing or

obsolescent suspension preheaters, and use in small plants.

Some possible options for aiding exploitation of the opportunities are: provision of government or industry insurance

against technical risks, government-instituted revolving loan

funds with low interest rates, industry-sponsored investment

systems and programs for development, higher cement prices,

. and the incentive provided by increases in fuel costs.

1) Use of Lower-Grade Heat

The use of the lower-grade heat which is usually wasted in

the cement plant poses an energy-saving opportunity. New attention should be given to the use of the lower-grade heat for

cement manufacture and the distribution of waste heat, or electricity manufactured from it, outside the cement plant. After

the fullest use of energy in the manufacturing process, space

heating would be the main use for heat at the lowest end of

the temperature spectrum. Constraints on the distribution of

heat and electricity outside the cement plant are the rate

structures and regulations concerning feeding from nonregulated generators into a regulated net, and community

attitudes towards industry. It is recommended that consideration be given to the use of the lower-grade heat for drying,

in-plant space heating, heating of fuel and raw materials,

community space heating, and process heating (as in paper

plants using low pressure steam).

m) Cogeneration of Electricity and/or Steam with Clinker

Cement plants can burn lower grade fuel and convert it to

electricity. This can be done with fuels which are not

suitable for use by power companies. The availability of steam

from waste heat boilers makes possible the use of direct drive

equipment running on steam and other uses of steam which do

not require conversion to electricity. Although many plants

which once operated in this way were shut down for technical

and economic reasons, these reasons may not be applicable

today. The cogeneration of electricity and/or steam with

clinker is most likely to be attractive in new processes where

it can be integrated into the design. It may also be economic

in existing modern plants, where preheaters and long kilns

permit gases to leave at reasonably high temperatures, and

in some older plants where it would increase fuel efficiency

and use existing steam/ electric equipment.

15
3.5 Research Needs

a) Coal Refuse as a Cement Raw Material

Coal refuse contains fuel values as well as lime, silica

and alumina. If it could be used in cement manufacture, it

would help conserve natural resources, including fuel, and contribute to the disposal of coal mining wastes. Although the

iron and alkali contents of coal refuse, and transportation

costs, may hinder its use, it is recommended that research be

carried out on the suitability of this type of refuse for use

in cement manufacture, including studies of the effects of sulfur, alkalies and trace elements on phase equilibria and cement

performance.

b) Flue Gas Desulfurization Wastes as Cement Raw Materials

Flue gas desulfurization (FGD) systems typically produce a

CaSOx waste material. Although their contents of sulfate, sulfite and iron might be detrimental, it appears these wastes

could be combined with fly ash to provide all the necessary

oxide constituents for portland cement manufacture. If FGD

wastes could be used in this way, it would help reduce a disposal problem and contribute to the conservation of natural

resources. It is recommended that possibilities for manufacturing cement from FGD wastes be explored. Since the cement

industry has no obvious economic incentive to support such

development, the support would probably have to come from governmental or institutional sources.

c) Sewage Treatment Waste as a Cement Raw Material

Sewage treatment waste has a potential fuel value and it

contains silica and lime. It can be generated in the form of

a wet sludge or a dry incinerator ash. If this material could

be used in cement manufacture, it would help to reduce waste

disposal problems and aid in the conservation of fuel and other

raw materials. It is recommended that the potential of this

waste for use in cement manufacture be investigated. The

research on the wastes should include investigations of the

range of compositions, heating values, methods of handling,

attendant environmental problems, and the economics of use.

d) Production of Portland Cement from High Surface Area Lime

High surface area lime can be produced by the rapid heating of calcium carbonate raw materials under a low partial

pressure of carbon dioxide. It is believed that the high

surface area lime would react more rapidly with silica,

alumina and iron oxide in the formation of portland clinker,

and with a lower requirement for energy. It is recommended

16
that research be carried out on the calcination of calcium

carbonates to form high surface area limes and that the energy

» costs and product quality be evaluated.

e) Separate Grinding of Raw Materials

The segregation of the components of the raw meal for cement manufacture can sometimes be traced to the variability in

the grinding rates of the raw materials. Because of segregation, longer burning times are needed for the meal and more

energy is used in clinker manufacture. Separate grinding of

the raw materials to the optimum fineness with subsequent blending would probably reduce the energy requirement for clinker

manufacture. Among potential benefits would be reduced fuel

requirements, improved product quality, reduced dust generation,

increased production, and conservation of materials by allowing

use of lower-quality materials.

f ) Dispersion of Raw Materials and Clinker During Grinding

Dispersing agents such as water, glycols, and other organic

compounds with polar molecules are commonly used as grinding

aids in the cement industry. In some cases, grinding aids tailored to a specific mill need have reduced the power required

for grinding by 10 to 15 percent. Unfortunately, the benefits

vary significantly with the application and the energy savings

have seldom been quantified. This is because past studies have

not been systematic and grinding aids have often been marketed

in terms of their effects on the flow properties of the dry

powder rather than on grinding efficiency. In order to help

establish the energy saving potential of increased use of grinding aids, it is recommended that research be carried out to

study the effects of grinding aids on energy requirements and

product characteristics. The research should include studies

of the dispersion phenomena in terms of their origin and the

factors affecting them, e.g., electrostatic forces, heat,

surface characteristics, etc. The results of such research

could help the industry understand conventional and new types

of dispersing agents, and increase the cement industry's ability

to select the proper agents for optimum energy reduction.

g) Thermal Comminution of Limestone and Other Raw Materials

It has been observed that aragonite, one of the naturallyoccurring forms of calcium carbonate, breaks up into micrometer

sized particles when heated in a conventional rotary kiln.

If the factors contributing to this reduction in particle size

on heating were understood, it might be possible to reduce the

energy requirement for clinker manufacture by inducing thermally-induced comminution within the kiln. It is recommended

that research be carried out on this phenomenon exhibited by

17
aragonite (which is abundantly available in the Caribbean

and Persian Gulf areas) and on the possibility of extending

application of the knowledge to other sources of calcium

carbonate.

Alternative Methods of Comminution

The conventional ball mills used for grinding cement raw

materials and clinker are very inefficient. It has been estimated that less than 5 percent of the energy put into the mill

is actually used in surface area generation. The finish grinding of cement consumes about 40 percent of the electrical

energy used in a cement plant equipped with a suspension

preheater kiln. Because of the high potential for reducing

the electrical energy used in cement manufacture if grinding

could be made more efficient, it is recommended that fundamental studies of milling be carried out in the search for more

efficient processes. Directions worthy of investigation might

be suggested by analyzing the Snyder process, the torroidal

steam autogenous mill, coal comminution processes, solvent

processes, and processes developed by the Syracuse Research

Corporation and by Russian technologists.

Electrical Heating of Kilns

It appears that several alternative energy sources could

only be used for clinker manufacture if electric power could

be used for heating a kiln. Among these alternative energy

sources are nuclear, solar, geothermal, wind, tidal, ocean

thermal, and photovoltaic. Unfortunately, with current technology, electrical heating is not economically attractive.

In view of the importance of determining the possibilities

of replacing fossil fuels with essentially renewable sources,

it is recommended that research be carried out on the feasibility of using electric power for the production of clinker.

Clinker as a By-Product of Coal-Fired Power Plants

The fluid-bed process for combustion of coal includes the

addition of limestone to the fuel bed to absorb sulfur dioxide.

The possibility that the conditions in the bed could be controlled so that the lime would also combine with the coal ash

to form a cementitious ash or an ash which was particularly

suitable for the manufacture of cement clinker should be

explored. Since such a process might have potential for

lowering the energy requirements for manufacture of hydraulic

cements, it is recommended that theoretical research be carried

out to determine the feasibility of such a process and, if

feasible, to extend the research to pilot plant and field

trials to determine the range of application and the fuel

efficiency.

18
k) Low-Temperature Processes for Cement Production

Although the present method of clinker production requires

a large input of energy to heat the raw materials to high temperatures, there is some evidence that cements can be formed

at much lower temperatures by mechanical action (grinding)

between lime and silicates. Lime can also be produced at lower

temperatures than are usually used. Because of the possibility

of eliminating the traditional cement kiln with its high energy

consumption, it is recommended that research be carried out on

the feasibility of low-temperature formation of cementitious

materials which could be substituted partially or completely

for portland cement. The initial efforts should be focused on

the low-temperature production of lime. If this is successful,

the low-temperature production of cement should be investigated.

1) Modeling of Clinker Production

Changes in the distribution of the oxides in the raw materials for portland clinker production and changes in kiln operating conditions affect the physical character of the clinker,

and the composition and distribution of the compounds in it.

These changes in turn affect cement performance. An improved

understanding of these relationships can be obtained through

development of mathematical models. Certain aspects of this

problem are fairly-well understood, particularly the basic

gas-solid heat exchange equations and certain relationships

involving raw material granulometry , chemistry and burning

zone profile. However, research is needed on the conditions

under which clinkering reactions take place and the critical

factors in the formation of minor compounds. Research is also

needed on the critical factors affecting the kinetics of coating

formation and clinker formation, including the temperature profile. All of these should be integrated in a comprehensive model which would have importance for improving kiln design, and

optimizing operations in regard to clinker quality, clinker

grindability , refractory life, and fuel consumption.

m) Phase Diagrams for Portland Cement Compositions with Mineralizers in Kiln Atmospheres

It is generally accepted that the use of mineralizers

(fluxes) in clinker production has potential for energy conservation. Although some phase "equilibria" data have been

obtained for the calcium f luoride-portland clinker system, and

for spurrite and its analogs occurring in the 1000-1100°C

temperature range, there is a need for more detailed information on phase relationships in systems containing fluorides,

chlorides, and sulfates with portland clinker compositions in

kiln atmospheres. Information is also needed on the effects

of mineralizers, individually and in the presence of others,

on:

19
1. Alkali volatilization,

2. Minor components such as MgO,

3. Melt viscosity,

4. Calcination temperature,

This information is needed to help in the selection of mineralizers

.

Measurement and Control of Clinkering by Microscopic Analysis

Improvement of clinker quality can lead to lower overall

costs of cement. Methods have been developed to monitor clinkering so as to maximize the performance potential of the clinker. However, more research is needed to complete the evaluation of the methods. Research is needed to provide knowledge

of the relationships between microscopic results and performance

characteristics of the resultant cement, such as setting time,

slump loss, rate of strength gain, and clinker grindability

.

If it could be developed, an automatic on-line sensor which

functioned as an analog to a microscopic analyzer would have an

important energy-saving potential. It is estimated that there

is a potential for saving at least 20% of the energy required

for cement manufacture.

Improvement of Clinker Grindability by Control of Cooling History

Portland clinkers can differ substantially in their grindability. The grindability is known to be affected by the rate

of cooling. Clinker is usually cooled by a stream of air in

reciprocating grate coolers, traveling grate coolers, or

planetary coolers. A portion of the air is recovered for use

as combustion air in pyroprocessing. The excess air is vented

through a dust collector or is used as a low-grade heat source.

Research is needed to determine if alternative cooling methods

might be developed which could improve clinker grindability

using thermal shock. Investigations should also be carried out

to determine if cooling media more energy-efficient than air

could be found in order to eliminate the capital and energy

costs of air cleaning. The possible benefits are more easily

ground clinker, more efficient cooling, and reduction or elimination of the need for air cleaning.

20
Removal of Undesirable Volatile Components from Cement Kilns

by Increasing Exhaust Temperatures

Heat recovery from the exhaust gases of cement kilns is

often hindered by the presence of undesirable vapors, such as

those of alkali sulphates and chlorides in the gases. Because

only low quantities of these salts can be tolerated in clinker,

their vapors should not be allowed to condense on the incoming

kiln feed. If the exhaust temperatures of the kilns could be

increased, this could aid in the removal of the undesirable

volatiles and help to optimize the total energy costs. Such

a process modification could only be economical if an adequate

heat recovery technology was available. Alternative energy

sources or new processes may require higher exhaust temperatures

so that systems with 100% separation (bypass) of the exhaust

gases from incoming feed could be considered without causing

an appreciable loss of efficiency. Research is needed to provide knowledge of the physical and chemical properties of high

temperature gases leaving the clinkering environment. This

knowledge would assist in the design of heat transfer equipment

needed in the development of new processes.

Reduction of Dust Generation in Clinker Manufacturing Processes

Dust represents a substantial loss of the energy expended

in quarrying, feed preparation, and, particularly, in pyroprocessing. There is, therefore, a need to carry out research

to evaluate the following possibilities for reducing dust

losses:

1. Separate preheating and/or calcining of raw material

components

2. Separate grinding of each raw material component to

minimize production of fines before entering the kiln

3. Better control of particle size in grinding the raw

material mix to minimize the quantity of unnecessarily

fine material entering the kiln

4. The use of mineralizers to allow the use of coarse raw

feed

5. Reducing gas flows by oxygen enrichment or the use of

noncombustion heat sources such as electrical or solar

6. Pelletizing the kiln feed, and

7. Using a fluid bed kiln.

21
r) High Temperature Dust Collectors

The need exists for the removal of dust from the exhaust

gas stream of cement kilns without appreciable lowering of the

temperature. For this purpose, it will be necessary to develop

a dust collector which will operate in the range of 1500-2500°F

(800-1350°C) . The benefits of removal of dust from the hot

stream will be much greater utilization of the heat in the

stream.

s ) Dust Recycling and Waste Heat Recovery

The ability to remove dust from hot gas streams will permit

greater use of the heat in the stream. It should be possible to

remove dust from cement kiln gases using a high temperature

cyclone collector. Since the alkali will probably stay in the

gas stream, this dust may be completely recycled. A waste heat

boiler could then be designed to remove the alkali and recover

the heat, the final dust collection being accomplished with a standard bag house collector. Research may be necessary to develop

a high temperature cyclone for use with a specially designed waste

heat boiler.

t ) The Effect of Clinker Structure on Grinding Energy Requirements

Research has shown that the energy required for grinding

is a function of the relation between the mean size of the

crystals to be ground and the mean particle size of the product.

Reductions of up to 25% in the amount of energy required for

grinding have been demonstrated by control of crystal size.

Research is now needed to determine the factors which govern

the crystal size in clinker and to test pertinent theoretical

explanations. Since the correlations between the crystallography and the grindability which are of concern are those

which are found in the processing plant, research in the plant

is needed with the results being documented and published. It

is recommended that researchers be given the opportunity to work

in a cement company to make plant level observations and correlate this data with laboratory grinds.

u) Alternatives to Electrical Energy for Driving Grinding Mills

Although electrical energy is most commonly used for driving grinding mills, other forms of energy could be used. For

example, drives can be driven directly with steam from waste

heat boilers and there are direct diesel drives. Because of the

desirability of substituting waste energy for diesel fuel, modern technology for direct steam drives should be evaluated.

22
v) Improvement in Efficiency of Particle Size Classification

Particle size classification is used to increase the

efficiency of grinding circuits. Present classifiers use air

and the efficiencies attained are between 30-60%. Energy is

lost in transporting the materials and as a result of mill

inefficiency. Research is needed on mechanisms or devices

for increasing the efficiency of particle size classification.

This could include the use of additives. The benefits would

be more efficient mill operation, reduced circulating loads

in mill circuits, and reduced capital costs.

w) Cogeneration of Electricity and Clinker

The cost of electric power is rising because of increasing

costs of fuel and plant investment. Cost penalties will be

developed for use of peak period power. Because it may be

necessary for the development of new pyroprocesses based on

alternative energy sources (e.g., nuclear, solar), research is

needed to provide knowledge of the physical and chemical properties of high temperature gases leaving the clinkering environment. This knowledge will assist in the design of heat transfer

equipment.

x) Reduction of Power Requirements for Cement Production

The production of a ton of cement requires an average of

135KWH of electric power at a cost of about $4. The fuel

requirement for production of a ton of cement is about 4 million

BTUs at a cost of about $5. Although there are well-defined

programs for reducing fuel consumption, there are none for

power reduction. It is therefore recommended that research be

carried out to determine how electric power requirements for

cement production can be reduced, and how the efficiency of

the equipment can be improved. A program similar to that which

exists for reduction of fuel consumption should be established.

Unresolved Issue

a) Feasibility of Complete Recycling of Dust when Using High

Sulfur Coal as Fuel

Increasing pressure is being placed on the cement industry

to use high sulfur coal. This results in the generation of

dusts with alkali and sulfur contents which are too high to

be tolerated in the product. On the other hand, return of dust

to the kiln is desirable for the sake of economy and efficiency.

It is not yet clear what the ultimate resolution of this problem

will be. It may depend on results of research on alkali and

sulfur compounds in the clinker. It is also possible that

23
a compromise on regulations regarding emissions and the types

of fuel permitted will have to be reached between DoE and EPA.

4. BLENDING MATERIALS

4.1 Background

For the purposes of this workshop the category of blending materials included chemical admixtures and pozzolanic and latent hydraulic

materials. Chemical admixtures are usually organic compounds or soluble

inorganic salts added to concrete in small amounts to modify water

requirement, air content, or setting time. Pozzolanic materials are

solids which, though not cementitious in themselves, are capable of

reacting with lime in the presence of water to produce cementitious

products. Latent hydraulic materials are solids which will react with

water to form cementitious products when activated, usually by exposure

to a high pH environment. Pozzolanic and latent hydraulic materials are

used in concrete in much larger proportions than chemical admixtures,

usually as partial replacements for portland cement. When these materials are interground with portland clinker or blended with portland

cement at a cement plant, the product is referred to as a blended

cement. When they are to be added to concrete at a job site they are

referred to as mineral admixtures.

4.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

a) Increased use of fly ash in cement and concrete

b) Increased use of slag in cement and concrete

c) Increased use of superplasticizers in concrete

Research Needs:

a) Standard test methods for chemical resistance of blended

cements

b) Accelerated tests for pozzolanic reactivity

c) Mechanism of pozzolanic reactions

d) Quality control and benef iciation of fly ash

e) Elevated temperature curing of concrete products containing

pozzolans

24
f) Reduction in variability of concrete performance through the

use of slag

g) Slag activators

h) Use of slags other than granulated blastfurnace slags

i) Special clinkers for use in blended cements

j) Optimization of slag hydraulicity

k) Use of superplasticizers with blended cements

1) Cement-admixture interactions

4.3 Summary of the Discussions

The working group on blending materials considered both admixtures

and materials suitable as partial replacements for portland cement.

Based on the criteria of availability, compositional suitability, uniformity and cost, it was agreed that increased use of fly ash and

blastfurnace slag could result in significant energy savings. The use

of superplasticizers to reduce the water content of concrete mixes was

also seen to have implications for energy conservation. None of the

opportunities had been fully exploited because of lack of knowledge about

reactions of the blending materials and the lack of adequate standard

test methods for evaluating performance. Comments on these matters are

contained in the three statements of energy-saving opportunities and

twelve statements of research needs which the group prepared.

4.4 Energy-Saving Opportunities

a) Increased Use of Fly Ash in Cement and Concrete

Energy can be conserved through the use of suitable fly ash

as a partial replacement for portland clinker in cement or for

Portland cement in concrete. The basic concrete mix design

principles are known and neither the supply of suitable fly

ash nor the economics of its use are limitations. However,

among constraints to fly ash use are the sometimes unnecessary

requirements for rapid strength development, inadequacies in

standard specifications and test methods, uncertainties

regarding the uniformity of fly ashes and the effects of their

variability, and institutional factors such as consumer acceptance and industry apathy. Apart from use in conventional

applications of concrete, other opportunities for use of fly ash

in concrete include use in special applications such as k-crete

and econocrete, and use in precast products cured at elevated

temperatures. It should be noted that some lignite and sub25
bituminous fly ashes have cementitious properties which might

be exploited. The immediate need is for dissemination of information about fly ash use in concrete and research to increase

knowledge of fly ash characteristics.

Increased Use of Slag in Cement and Concrete

Suitably granulated blastfurnace slags have latent hydraulicity. As a result, when ground granulated blastfurnace slags

are properly activated, they can be used as partial replacements

of portland cement. A major constraint on such energy-saving

use is that the amount of granulated slag currently produced

in the U.S. is very small.

Increased Use of Superplasticizers in Concrete

Superplasticizers can lower the water requirements for concrete and increase its strength. This has energy-conserving

implications because lower water requirements result in improved

concrete durability and make possible a reduction in the cement

content of concrete. While the use of superplasticizers is

growing, their use could probably be increased by improved dissemination of information about them.

4.5 Research Needs

a) Standard Test Methods for Chemical Resistance of Blended Cements

Concretes containing blended cements have often demonstrated chemical resistance and durability superior to that of concretes made with Type I portland cements. However, the use of

blended cements in applications where chemical resistance is

important has been limited by the inadequacies of standard specifications and test methods. This barrier could be overcome

by the development of standard tests for the durability of

cements, particularly in the areas of sulfate resistance,

alkali-aggregate reactivity and soundness. New or improved

standards would facilitate the use of blended cements by

providing objective bases for comparison with the various types

of portland cements.

b) Accelerated Tests for Pozzolanic Reactivity

Current tests for pozzolans for use in cement and concrete

require 28 days for completion. This is much longer than is

desirable for acceptance tests. It is recommended that research

be carried out to provide the technical basis for the establishment of more rapid acceptance tests for fly ashes and other

pozzolans.

26
Mechanisms of Pozzolanic Reactions

Understanding of the rate-controlling factors in pozzolanic reactions would almost certainly broaden the potential

applications for pozzolans. It should lead to development of

methods for increasing the rate of strength development of

pozzolan-containing cements and concretes and make possible

higher levels of cement replacement. It should also help in

the identification of possibilities for benefication of fly

ashes to obtain improved performance, the evaluation of

pozzolanic potential of waste materials other than fly ash,

and optimization of pozzolan use as, for example, by use of

elevated curing temperatures.

Quality Control and Benefication of Fly Ash

Fly ash varies considerably depending on the sources of

the parent coal. This variability hinders ash use in cement

and concrete because of uncertainty about its effects. There

is a need to quantify the effects of ash variability on the

performance of concrete. This could lead to improved quality

control, to improved beneficiation procedures for improving

ash quality, and to higher levels of use of ash in cement

and concrete.

Elevated Temperature Curing of Concrete Products Containing

Pozzolans

Elevated temperature curing of concrete allows the use

of higher levels of replacement of portland cement by pozzolan.

Energy savings would result from research which would lead to

guidelines for optimization of concrete mix designs taking into

account the rates of strength development required and the

curing conditions available. This could, in addition, encourage

the use of waste and by-product materials not currently used

in construction as replacements for traditional materials with

a high energy requirement for their production, such as silica

flour, and stimulate the development of new types of precast

building materials.

Reduction in Variability of Concrete Performance Through the

Use of Slag

There are indications that the blending of separatelyground, granulated blastfurnace slag with portland cement can

decrease the variability in 28 day strength. Research is needed

to confirm this effect and to provide a sound basis for its

exploitation. This would allow more efficient use of concrete

since less overdesign would be required. A current constraint

is that suitable granulated slags are not produced in the U.S.

27
Slag Activators

The use of granulated blastfurnace slag in cement is limited in some applications because it tends to reduce the rate

of strength development. Research needs to be carried out to

identify improved activators for slag-containing cements so as

to broaden their potential range of applications.

Use of Slags Other Than Granulated Blastfurnace Slags

The use of granulated iron blastfurnace slags in cement is

well-established in many foreign countries. However, there

appears to be additional potential for energy savings by using

slags from other industries or the use of blastfurnace slags

which are partially crystalline. Research is needed to evaluate

other slags, such as phosphate slags and pelletized "air granulated" blastfurnace slags, for use as cementitious materials.

Special Clinkers for Use in Blended Cements

Slags and pozzolans differ in their chemical characteristics and reactivities. It is not known whether the compositions

of currently produced portland cement clinkers are close to the

optimum for use with them in blended cements. Higher free lime

clinkers might offer a potential for more rapid strength development of blended cements while lowering the energy requirements

for clinker production. Research is needed to confirm this and

to assess its implications for energy conservation.

Optimization of Slag Hydraulicity

Performance of slags in cement and concrete is related to

composition, glass content, and fineness. There is a need to

investigate the relationship between slag fineness and strength

development in slag-containing cements. The study should extend

well beyond the range of finenesses normally used and should

include assessment of the effects of the particle size

distributions. The effects of fineness and particle size

distribution on other properties such as air entrainment and

workability should also be considered. This could increase the

potential application of slag-containing cements by improving

their rates of strength development and ultimate strengths.

Use of Superplasticizers With Blended Cements

The use of superplasticizers in blended cement concretes

has the potential for increasing the rate of strength gain and

for lowering the cement content needed. The use of less expensive blending materials, such as fly ash or slag, should compensate for the cost of the superplasticizer. Research is

needed to develop a more complete understanding of the inter28
action of superplasticizers (and other admixtures) with cements,

pozzolans, and slags and to explore ways of reducing admixture

consumption by the unburned carbon usually present in fly ash.

The research should include work on concretes containing superplasticizers .

1) Cement-Admixture Interactions

Admixture behavior in concrete depends on cement composition, temperature, time of addition, and dosage. Changes in

these factors can lead to variability in setting behavior, water

requirement and workability. In many cases these changes cannot

be predicted. Research is needed to elucidate the mechanisms

of water reduction to develop an understanding of the rheological properties of concrete of low water-cement ratio, and

to elucidate the effects of admixtures on the chemistry of cement hydration, on the properties of the cement hydration products, and on the microstructure of hardened cement pastes and

concretes in order to improve our capabilities for the prediction of concrete performance.

5. CONCRETE PRODUCTION

5.1 Background

Concrete is the most widely used construction material in the United

States and accounts for about 75% by mass of all the construction materials consumed annually. The major constituents of concrete are cement,

sand, aggregate, admixtures, and mixing water with significant amounts

of steel being used in reinforced concrete. Roughly 65% of the concrete

placed in the United States is proportioned at ready mix plants and

transported to the sites of construction. Approximately 5% of the concrete placed contains mineral admixtures.

5.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

a) Optimization of the batching sequence

b) Test methods and compliance criteria

c) Production control methods

d) Improved thermal resistance through water reduction

e) Water-reducing, strength-improving admixtures

f) Specification of strength at the required age

29
g) Information on the performance of cement

h) Long-term cost and energy benefits of concrete

i) Maintenance of pavements and bridge decks

j) By-product and marginal aggregate materials

k) Unnecessary curing requirements

1) Energy-efficient design and maintenance of concrete plants

m) Heating and cooling requirements for plastic concrete

n) Conservation of heat contained in concrete aggregates

o) Conservation of heat contained in cements

p) Packaged forming and automatic self-curing systems for

concrete castings

q) Thermal shock requirements for reinforced concrete

Research Needs:

a) Fuel use in concrete production

b) Energy requirement for mixing of concrete

c) Energy consumed in transporting concrete

d) Optimization of the transportation network

e) Energy required in placing concrete

f) Curing requirements for different end uses

g) Alternatives to accelerated curing in block manufacture

h) Reduction of corrosion of steel reinforcement

Unresolved Issue:

a) Incentives for cost-effective research and development in the

cement and concrete products industries.

5.3 Summary of the Discussions

The working group on concrete production considered existing oppor

tunities for saving energy in the production of concrete and research

30
needed in seeking additional energy conserving possibilities.

Attention was given to each of the operations inherent in the

production, handling, and transportation processes. This included

the use of optimized batching sequences in charging mixes and the

use of well-designed, carefully-inspected production plants audited

for energy consumption.

The possibilities for changing specification requirements to make more

efficient use of materials and energy were discussed as were possibilities for the use of insulation to retain heat generated during cement

hydration. The potential benefits from use of water-reducing and other

admixtures, marginal aggregates, and the partial substitution of fly ash

or ground granulated blastfurnace slags for portland cement were also

considered. An unresolved issue concerned incentives for cost-effective

research in the cement and concrete industries. The 17 energy-saving

opportunities and the 7 research needs which the group identified are

outlined below.

5.4 Energy-Saving Opportunities

a) Optimization of the Batching Sequence

The performance of concrete is affected by the sequence

in which the ingredients are added to the mixer. For example,

the effect of the addition of a chemical admixture can vary

depending on the delay time following the first mixing of

cement and water. It is important that the personnel of

concrete plants should be properly trained so as to understand

the effects of improper batching on the quality and performance

of the finished product.

b) Test Methods and Compliance Criteria

Uncertain test results may lead to the rejection, demolition and rebuilding of supposedly defective concrete structures with a consequent waste of energy. To avoid this,

improvements in the accuracy and precision of all concrete test

methods are needed and realistic compliance criteria based on

the test methods should be established. Problems are caused

by a lack of understanding of the inherent variability of all

tests for cement and concrete, the apparent belief by specifiers that results on test reports are indisputable, and the

lack of standards of performance for testing laboratories. It

is recommended that national and international standards be

established which define the test methods and provide for

regular verification of the methods. It is also recommended

that standards for testing laboratories and facilities be

established.

31
Production Control Methods

The quality of concrete made to a given specification is

usually quite variable. As a result, there is a tendency to

require concrete and its ingredients to be of unnecessarily

high quality. Improvements in production control methods which

would result in the production of more uniform concrete could

lead to savings in energy by reducing the requirements for

cement and processed aggregates. Related factors are the

demand by specifiers for concrete and concrete materials of

unnecessarily high quality and unrealistic code requirements

which restrict the producer's options and prevent him from usin

his expertise. Among steps which could be taken to reduce the

waste of energy are to seek recognition of existing production

control principles in codes of practice and to provide training

courses on production control methods. Improved production

control could lead to reduction of design safety factors and

more efficient use of materials, whether of low or high quality

Improved Thermal Resistance through Water Reduction

The quantity of water in hardened concrete in the exterior

of buildings is governed by the porosity of the concrete and

should be minimized if advantage is to be taken of the inherent

thermal resistance of concrete. This is because the thermal

conductivity of water is higher than that of the other constituents of concrete. Unfortunately, construction practices and

attitudes favor the use of relatively high water-cement ratios

to obtain good workability. Other ways of obtaining good

workability without such high water-cement ratios are through

carefully-controlled additions of superplasticizers or fly ash

to the concrete, or by vacuum de-watering after placing. To

achieve the benefits of reduced water contents, it is recommended that changes be sought in the specification requirements

and attention be drawn to the potential benefits through educational programs for concrete technologists, building owners and

other decision makers. The energy savings will be cumulative

throughout the life of the structure and will result in reduced

life-cycle costs.

Water -Reducing , Strength-Improving Admixtures

In general, reduction in the quantity of water in a concrete mix increases the ultimate strength. For this reason,

increased use of water-reducing, strength-improving chemical

admixtures can save energy by reducing the required cement content of concretes. At present, about 50% of all concrete produced in the U.S. includes such admixtures and it appears the

percentage can be increased much further. The principal constraints to increased use of these admixtures are prescriptive

rather than performance specifications and the difficulty in

32
predicting and controlling performance. With certain cement

compositions, admixtures may do little to increase strength and

may even cause strength reductions. The variability of

cement-admixture performance resulting from variations in either

the cement or the admixture is a frequent problem. Additional

research is needed to identify appropriate selection and control

procedures. Further, the possible energy savings from the use

of admixtures should be considered in determining the composition of the cement produced. Although present U.S. cement

specifications do not permit the inclusion of these chemical

admixtures in the manufactured cement, this is not a major constraint since it is probably best to add the admixtures during

the mixing of the concrete, even though a greater quantity of

admixture per unit weight of cement may be required.

Specification of Strength at the Required Age

Present building codes and codes of practice traditionally

use the 28-day strength of a concrete as the final quality control standard of its strength potential. This frequently leads

to a requirement for unnecessarily high strength at 28 days when

the structure may not be loaded for a much longer period. While

recognizing that delay in acceptance of the concrete could cause

some inconvenience if acceptance was based on strength at later

ages, it is recommended that provision be made for structures

which have long construction periods to be accepted on the basis

of the 56-day, or other appropriate age, strength. This would

require ACI to provide for use of different test ages for structures having construction periods of different lengths.

Information on the Performance of Cement

It appears that producers of concrete could adjust their

mixes to produce concretes of more uniform strength if cement

producers would supply them with more information. This is

done in Australia where results of tests in the cement plant

laboratory are sent by teletype to users as soon as possible

following shipment. This would require cement companies to have

concrete laboratory facilities, to keep records of the origin

of individual shipments and, possibly, to store the cement for

an extra day or two before shipment. The cement plant could

use the accelerated tests now used in control of ready mix

concrete, but the exact details of the tests would have to be

developed. As an example, it might be possible to establish

that a mill run composite of a silo yielded results representative of all shipments from that silo.

33
Long-Term Costs and Energy Benefits of Concrete

It is believed there are many applications where the total

lifecycle costs and energy use of concrete structures are superior to those of competing materials. Examples are concrete

building enclosures which benefit from the thermal inertia of

concrete, underground housing, heat transfer and storage systems, and concrete pavements. However, because of the difficulty in quantifying the energy savings, no organized approach

to their evaluation has been developed. It is therefore suggested that technical support efforts should be provided to

document the long-term cost and energy benefits of specific

applications of concrete.

Maintenance of Pavements and Bridge Decks

Traffic delays due to maintenance work on concrete pavements and bridge decks cause significant wastes of energy. The

waste could be reduced if the repairs could be made more

rapidly. The use of rapid-setting cements and special concrete

formulations can help achieve this objective. Constraints to

their use are state and other government specifications based

on conventional concrete techniques, the high first costs of

some products, and inadequate knowledge about the durability of

others. Energy conservation would be assisted by more effective

dissemination of information about the availability and properties of suitable materials. This could possibly be assisted

through a Transportation Research Board-sponsored synthesis

project.

By-Product and Marginal Aggregate Materials

Manufactured fine aggregates (sands) which are currently

available can be used successfully in many concrete applications. In many cases, these aggregates are manufactured from

by-product or waste materials and the processing required is

usually less than for natural sands. Local specifications and

lack of familiarity with the materials provide barriers to the

use of the manufactured sands in concrete. It is recommended

that acceptance of sands of this type be encouraged through

dissemination of performance data, enlistment of the support

of appropriate technical organizations, and revision of specifications .

Unnecessary Curing Requirements

The heat curing of concrete requires a considerable amount

of energy. New developments in casting, curing and materials

technologies make possible much shorter heat curing cycles than

present specifications allow. If prescriptive specifications

could be supplemented by performance specifications, this could

34
lead to large reductions in fuel consumption. It is recommended

that incentives be provided to contractors, precasters, state

highway departments, etc., to investigate the use of new materials, new construction methods, and shorter curing periods.

1) Energy-Efficient Design and Maintenance of Concrete Plants

The plant layouts and the operating and maintenance procedures of many ready mix and pre-cast concrete plants result in

waste of energy. Examples are the unnecessary handling and

transportation of concrete, leaks in air and steam lines, uninsulated and leaky steam kilns, idling machinery, and inefficient

means of heating and cooling. Unfortunately, the additional

effort and maintenance required to reduce the energy losses,

and the apparent low return on the investment, mitigate the

effects of the effort made. It is recommended that programs

be developed for carrying out energy audits of existing and proposed new plants to assist in identification of inef f iciences

and methods for their correction.

m) Heating and Cooling Requirements for Plastic Concrete

In many cases, plastic concrete must be heated or cooled

by energy-intensive methods to meet specification requirements.

Even though a combination of different curing conditions and

chemical admixtures can reduce the energy expenditures while

providing concrete of the required quality, current specifications and construction practices emphasize temperature

control. It is recommended that specification writing bodies,

especially ACI, be encouraged to include alternatives to temperature control in their specifications and to recommend construction practices which do not require temperature control.

n) Conservation of Heat Contained in Concrete Aggregates

Stockpiles of concrete aggregates are subject to seasonal

changes in temperature. When an aggregate is moved from a stockpile to a storage bin, the material is usually taken from

the exterior where the temperature variations are the greatest,

rather than the interior where the variations are the least.

Although additional capital expenditures are required to construct structures and equipment for withdrawing materials from

the interior of a pile, it is recommended that this approach

be promoted to minimize the need for cooling aggregates in summer and heating them in winter. This could be accomplished

through publication of recommended practices and procedures for

the storage of aggregates to minimize the effects of external

temperature variations.

35
Conservation of Heat Contained in Cements

Good concrete practice suggests that hot cement should

not be supplied to the job in summer although it could be

desirable in winter. Using available technology, it appears

that hot cement could be delivered to insulated bins at concrete

plants to produce warmer concrete in winter. It should also

be possible to use solar or other naturally-heated systems for

heating water and other concrete materials in winter. This

would be analogous to the practice in the asphalt industry

of maintaining the temperature of hot asphalt during delivery

so as to reduce the mix plant's energy use. The asphalt industry

is also experimenting with the use of solar heat to keep surge

bins and storage tanks hot.

Packaged Forming and Automatic Self-Curing Systems for

Concrete Castings

The pre-cast concrete industry uses highly-insulated forms

so that much of the heat liberated during the hydration of the

Portland cement is retained. This heat, which accelerates the

strength gain, is available at no cost. Form manufacturers

should be encouraged to market self-contained forming and curing

systems which utilize efficient insulation. Such forming systems should include automatic systems (master-slave systems) for

curing the quality control specimens under the same

time-temperature history as the concrete in the insulated forms.

Automatic master-slave curing systems should also be used for

concrete structures and the associated quality control specimens

at the construction site. Complete packaged forming and

self-curing systems with master-slave curing systems for quality

control specimens are available from electrical controls companies. Automatic curing systems can make possible much shorter

curing periods through a combination of internal exothermic

heating and external heating applied for a short time. Specifications will need to be modified to allow these shorter curing

periods. Industry acceptance of such systems would be stimulated if they were recognized by state highway departments,

since these departments have the most rigid specifications for

casting, curing and quality control.

Thermal Shock Requirements for Reinforced Concrete

Limitations on the rate of cooling of winter concrete in

cases where restraint of volume change is minimal or the content

and distribution of steel is adequate for crack control should

be reviewed. At present, the specifications do not properly

distinguish between conditions where thermal shock is important

and where its effects are minimal. It appears that the requirements could be modified to allow the use of energy-saving curing

methods including the use of insulated forms, and shorter

periods of high temperature curing and controlled cooling.

36
5.5 Research Needs

a) Fuel Use in Concrete Production

Energy conservation efforts relating to the production and

use of concrete will be assisted if quantitative data can be

made available on fuel use factors for all materials and

operations. The opportunities can then be assessed on a rational basis. It is, therefore, recommended that research be

carried out to identify the fuel use factors per unit mass of

concrete and concrete materials. This should include the energy

used in the production of the materials, and in transportation,

processing, and storage. A data base on fuel use factors would

enable private sector firms and government agencies to evaluate

opportunities for energy conservation and reduction of materials

and construction costs in the production and use of concrete.

b) Energy Requirement for Mixing Concrete

There are many different types of central plant mixers,

truck mounted mixers, and non-agitating units for the mixing

of concrete. However, the optimum combination of mixer and

batching sequence for minimizing energy consumption is not yet

known. It is recommended that research be carried out on mixers

and batching sequences to identify ways of minimizing the mixing

time and energy consumption. It is believed there are significant opportunities for energy conservation although the magnitude is not readily determinable. If it is assumed that the

mixing function consumes ten percent of the energy used in the

manufacture and delivery of ready mixed concrete, it is conceivable this could be reduced by at least half.

c) Energy Consumed In Transporting Concrete

Truck size, engine size and type, concrete capacity, and

truck routing strategies are among the factors which influence

the amounts of energy used in transporting concrete. In

general, the relative importance of these factors is not known

so the energy conservation benefits of changing concrete transportation practices and equipment cannot be assessed. It is

recommended that research be undertaken to identify the quantities of energy consumed in various concrete transportation

activities and the quantities of energy which could be saved

through changes which might be effected. Since about 80 to 90

percent of the energy used in mixing and delivering ready mixed

concrete is consumed in the transportation operation, it is

believed this information could lead to substantial energy

savings. In addition, improved practices in concrete transportation could increase the profitability of the ready mixed

concrete industry, reduce costs for concrete construction, and

retard inflationary price increases.

37
Optimization of the Transportation Network

Analysis of the total system of concrete and materials

transportation is needed if energy is to be used most efficiently. Factors influencing energy use include the location

of production facilities relative to material supplies and customers, methods of transportation available, and local environmental and zoning considerations. It is recommended that a methodology be developed for the analysis of the total transportation system for concrete and its constituent materials,

and that it be used to determine the most efficient use of

energy. This would lead to conservation of energy and increased

efficiency in the transportation of concrete and related materials .

Energy Required in Placing Concrete

There are many techniques for placing concrete but little

is known about the energy used in each. Further, the placing

method affects the properties of the concrete and, therefore,

the energy content of the constituent materials. It is

recommended that the energy used in placing by pump, crane and

bucket, belt, chute and buggy should be evaluated. The effects

of mix proportions, mix properties, and the concrete materials

necessary for successful application of the various placing

methods should be taken into account since they affect the

energy required in placing. It is believed that the physical

placing methods, except for their effects on mix composition,

only consume a small portion of the total energy used in concrete construction.

Curing Requirements for Different End Uses

Under certain conditions, satisfactory concrete can be

obtained with little or no additional curing after placement.

The exact conditions under which curing can be minimized or

eliminated for a particular end use are generally not known

and need to be delineated. It is, therefore, recommended that

research be carried out to determine the conditions under which

curing can be eliminated without adverse effects on the required

strength, durability, appearance, and other characteristics of

a concrete product or type of construction; the minimum curing

necessary to obtain a particular level of quality should also

be established. The establishment of criteria for minimum

curing requirements would lead to more efficient use of materials and energy.

38
g) Alternatives to Accelerated Curing in Block Manufacture

Current practices in the manufacture of concrete block use

energy-intensive methods of accelerated curing to achieve the

early strength needed for the rapid cycling of production

facilities. The curing accounts for five to ten percent of the

unit manufacturing cost and it is believed that the energy

requirements could be reduced by at least 50% through the use

of alternative methods of curing. It is, therefore, recommended

that research be carried out to develop ways of minimizing

energy consumption in the concrete block curing process through

new techniques in control of cement hydration. The benefits

could be complete elimination of fuel used in the curing of

concrete block, with attendant reductions in capital and maintenance costs.

h) Reduction of Corrosion of Steel Reinforcement

Significant losses due to the corrosion of reinforcing

steel in concrete structures exposed to salt occur even when

good concrete quality control has been exercised, since corrosion reduces the life of these structures. It has also been

reported that corrosion of reinforcement in foamed concrete

limits the continued use of this insulating concrete. It is

therefore recommended that research be carried out to

(1) develop improved guidelines for the quality of concrete and

depth of cover required for reinforced concrete subjected to

salt exposures, and (2) find ways of reducing the rate of corrosion of steel in concretes, such as foam concrete, which have

a high permeability to air and moisture. Among the possibilities which should be investigated are alternatives to regular

steel reinforcement or the use of organic and inorganic coatings

on the steel.

5.6 Unresolved Issue

a) Incentives for Cost-Ef fective Research and Development in the

Cement and Concrete Products Industries

There appears to be a lack of economic incentives for innovative, cost-effective research and development in the cement

and concrete products industries. This is an important problem

because cost-effective research would help stem the inflow of

foreign capital and technology by the Year 2000 and would help

reduce energy use in the manufacture and application of concrete

products. Indeed, it impacts on the foundation of modern

society since there is no alternative to a viable cement and

concrete industry. By its nature, the industry is presently

39
one of

impact

our most energy-intensive industries.* Factors which

on the problem are:

Inflow of foreign capital

Fragmentation of the industry, both horizontally and

vertically

Adverse effects of some legislation and government

regulation

Inadequate tax legislation

Depletion and depreciation

Inadequate transfer of information to decision makers

Possible adverse effects of government requirements and

procurements

Insufficient support by government of cost-effective

basic research for the cement and concrete industry

Restrictive effects of codes and zoning.

It is recommended that an in-depth business systems analysis

be undertaken on the effects on prof itibility of the introduction of energy-saving innovations into the system on a continuing basis. Research is also needed to develop in situ performance and durability standards for concrete to protect the

consumer and establish life-cycle costs. A second workshop

should be organized for high level government and industrial

decision makers showing the result of this workshop in dollars

and cents. A coordination center for cement and concrete

research, technology development, and information documentation

and retrieval should be established. Relevant solutions adopted

in Europe and Japan, including low-cost loans and government

cost-sharing in the development of innovative industrial processes should be examined.

It is the 6th most energy-intensive industry (Editor's note)

40
6. EFFICIENT USE OF CONCRETE

6.1 Background

Efficient use of concrete is closely linked with concrete production, cement production, and blending materials. Variability in any com

ponent of concrete ultimately results in variability in concrete performance. Because of the variability of concrete, concrete structures

are frequently highly overdesigned. Efficient use of concrete requires

careful consideration of both mix design and structural design, proper

selection of cement, consideration of the trade-offs between site placement of concrete and the use of precast elements, and ensuring the

required service lives of structures.

6.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

Application of generally-accepted practices and principles

of concrete technology

Tailoring of concrete to meet functional and environmental need

Accelerated testing

Certification for energy saving

Two-course construction

Innovative consolidation techniques

Use of ultra-rapid hardening cements

Very high strength concrete

Precast concrete

Concrete for special structures

Use of slags in concrete

Recycled concrete as aggregate

Fiber-reinforced cements and concretes

Autoclaved calcium silicates and other alternative materials

for concrete

Polymer and sulfur concretes

Titanium alloy reinforcing bars

41
Research Needs:

Waste or by-product utilization

Recycled concrete as a source of cementitious materials

Fiber-reinforced concrete

Ferrocement

Polymer- or sulfur-modified concrete

New lightweight aggregates

Phase change materials

6.3 Summary of the Discussions

The working group on efficient use of concrete perceived that energy

is wasted in the concrete industry chiefly by the failure to tailor concrete properly to its functional and environmental needs. This is

apparent from several of the recommendations. Prescriptive specifications, which require the concrete to contain a specific (or exceed

a minimum) cement content, have a large effect on the efficient use of

concrete. Because the greatest opportunity for energy savings lies in

the reduction of the cement content to the minimum required, such specifications prevent significant energy savings. If only the functional and

environmental requirements of the concrete to be used in a particular

application were specified, the producer could apply ingenuity to produce

an acceptable concrete with minimum energy input. This tailoring concept

is also evident in proposals for the use of two-course construction in

which concrete of high quality, or of particular environmental resistance, is combined with other concrete not exposed to the aggresive

environment; to extend the use of ferrocement, fiber concrete and

polymer concrete; and to build special structures out of a sophisticated

laminated system.

Although an obvious contribution of concrete to the conservation of

energy is the use of the thermal properties of concrete in enclosing

space in buildings, this was not considered in-depth since it was deemed

to be outside the scope of the workshop.

Recycled concrete was regarded as a source of both aggregate and

cement and was considered in detail, as was precast concrete. It was

recognized that essential factors in the implementation of the proposed

techniques would require technology transfer to the man in the field and

the certification of workmen and inspectors. The working group identified 17 energy-saving opportunities and 7 research needs.

42
6.4 Energy-Saving Opportunities

a) Application of Generally-Accepted Practices and Principles

of Concrete Technology

Failure to apply generally-accepted practices and principles of concrete technology often results in excessive use of

energy. Examples of energy-intensive practices are (1) the use

of higher cement contents than are needed to meet service conditions, (2) the limited use of blended cements and pozzolans,

and (3) the requirement of low-alkali cements in the absence

of proven reactive aggregates. Energy conservation will result

from definition of different service conditions, whether for

different structures or different portions of the same structure, and selective use of materials to meet these different

conditions. Practices which improve the uniformity of concrete

also conserve energy directly or indirectly. To take advantage

of these opportunities, there is a need to transfer known technology but, at present, there is a lack of training materials

and publications with an emphasis on energy conservation. A

related problem is the lack of access to foreign literature.

Steps which could be taken to promote the transfer of technology

are the organization of seminars for specification writers,

design engineers, local agencies, and concrete producers. The

seminars could be organized by the ACI and industry groups.

Agencies preparing recommended practices and technical documents

should be encouraged to emphasize energy conservation. Wellinformed technical representatives from industry and trade

associations with field contacts (similar to those which the

PCA had some years ago) would be useful. There is also a need

for a foreign translation service.

b) Tailoring of Concrete to Meet Functional and Environmental Needs

Unnecessarily high cement contents are frequently used in

concrete because of specifications requiring minimum cement contents. There is, in addition, reluctance on the part of concrete specifiers to select cement based on the environmental

conditions to which the concrete will be subjected. If specifications permitted the tailoring of concrete to meet functional

and environmental needs, this would avoid over-specification and

reduce the use of cement. It is recommended that prescriptive

specifications be eliminated so that determinations can be made

for each project as to the type of concrete actually needed.

c) Accelerated Testing

Almost all codes and specifications require that concrete

be evaluated by its 28-day strength; accelerated testing to

assess strength development is not recognized. If earlier

assessments of concrete acceptability could be made, the

43
producer could react more quickly to changes in strength levels

and allow a reduction in the margin of safety above the design

strength. This would result in a savings of both cement and

energy. It is recommended that codes and specifications be

revised so that concrete may be accepted on the basis of accelerated tests when these tests have been correlated with 28-day

tests using job materials. At the same time, design procedures

should be changed so that design could be based on accelerated

strength tests instead of 28-day strengths.

Certification for Energy Saving

Quality assurance of concrete would save energy by eliminating the waste which results from overdesign and overspecification. It would also reduce the overall costs of

concrete and encourage the substitution of concrete for steel,

which requires more energy to manufacture. As an essential part

of the quality assurance program, it is recommended that a system of certification of field personnel (supervisors, foremen,

inspectors, etc.) be established with a licensing system for

those qualified to work with concrete. With such quality

assurance, more use could be made of performance specifications

through which concrete would be tailored to needs, thus savings

materials and energy. Prescriptive specifications, which tend

to be costly and wasteful, would become unnecessary provided

adequate quality assurance was provided at the construction

level. At present, it appears that the industry does not fully

realize the waste of energy and materials caused by the present

system. A possible approach to a certification program would be

through political jurisdictions or professional societies.

Two-Course Construction

Normal concrete is relatively weak and the aggregates in it

are unlikely to be superior in durability or other performance

characteristics such as susceptibility to polishing. Better use

of concrete materials can be made by using a facing concrete of

the desired properties for the surface of a concrete member

while using slightly inferior concrete for the interior which

may account for as much as 7 5% of the total volume. Examples

are (1) bridge decks of conventional concrete with a two-inch

cover of latex-modified concrete for chloride protection, (2)

highway pavements with a thick course of regular concrete overlaid with two-inches of high quality concrete containing aggregates which provide good skid resistance, and (3) concrete beams

with flanges of fiber-reinforced concrete attached to webs of

less expensive concrete. It is recommended that opportunities

be provided for designers/constructors to be innovative in using

different quality materials in sandwich-type configurations to

produce the surface properties needed, while using less expensive fillers where the properties are less demanding. This

44
could lead to significant savings of energy. However, it should

be noted that the placing of such concretes requires exceptional

care and inspection to see that the work is done properly. Cold

joints can seldom be tolerated and the different concretes must

be compatible, particularly in thermal properties, if premature

deterioration is to be avoided. The principle of two-course

construction has been used successfully in dams, panels with

exposed aggregate surfaces, bridge decks, and pavements.

Innovative Consolidation Techniques

In the past, economic conditions have favored the use of

workable concrete which minimizes manpower requirements and

facilitates high rates of production. Unfortunately, the high

water contents used to obtain workability can lead to requirements for high cement contents. Innovative consolidation techniques, such as the use of roller compactors, large internal

and external vibrators, heavy drop tables, and vacuum dewatering

devices, make possible the use of less workable concrete. The

reduction in the water content of concrete leads to energy

saving through reduction in cement use; however, these techniques will only be used if the savings in cement are sufficient

to offset the costs of these special consolidation techniques.

Use of Ultra-Rapid Hardening Cements

Ultra-rapid hardening cements have potential for conserving energy in applications such as the rapid repair of

transportation facilities and cold weather concreting where they

may be used without the need for external heating. They are

particularly useful for reducing the cycle time in precast

concrete plants without the need for steam curing.

Very High Strength Concrete

Very high strength concrete can reduce the volume of concrete needed in compression members and some flexural members.

Because of the smaller quantity of material used, the total

energy required is below that for lower strength concretes. In

addition, the use of high strength concrete extends the possibilities for replacement of other materials such as steel.

The lower columns in high rise structures and the towers of

cable-supported bridges are ideal uses of very high strength

concretes. The use of very high strength concretes requires

careful control of all aspects of production including material

selection. High strength aggregates are required and the

required concrete strengths may not be achieved for two or three

months. Special consideration must be given in design to the

control of deflections and it must be recognized that very

high strength concretes may be much more brittle and notch sensitive than lower strength concretes.

45
i) Precast Concrete

Energy can be conserved by using precast concrete rather

than cast-in-place concrete for many applications. Some of

the constraints to the optimum use of precast concrete are

(1) the need for research on materials quality, predictability,

and methods of test, (2) the need for research on new materials

to achieve weight reduction and architectural design flexibility, (3) the energy consumed in transporting elements cast off

site, (4) lack of building designs providing repetition and

simplified joinery, (5) reluctance by builders to accept the

challenge and risk, of innovation, and (6) the need to provide

extra strength for temporary lifting during erection, as for

thin walls. Among the benefits to be achieved are savings in

the time taken to complete the work with resultant savings in

the energy used in support activities; reduced needs for form

materials; possibilities for incorporation of fiber-reinforced

concrete and various polymer-containing concretes; reduced use

of energy for curing which may be achieved by the use of

ultra-rapid hardening cements; reduced use of energy for manpower support facilities; improved quality control resulting in

more precise concrete design and reduced quantities of material

used in equivalent elements.

j) Concrete for Special Structures

Although the amount of concrete used for special structures is comparatively small, the amount of energy which may

eventually be saved may be considerable. In many cases, only

the surface layer or other limited portion of a structure has

to meet special requirements such as toughness or high erosion

resistance. Energy savings may be achieved through use of

specially-tailored composite concrete members. For example, the

safety containment for a nuclear power plant could consist of

a layered structure with an energy-absorbing outer cover to provide the necessary impact resistance, the whole requiring less

energy than a conventionally-reinforced concrete shell. Another

example might be in offshore and shore protection structures

which require high erosion and cavitation resistance in the

immediate vicinity of the surface. The bulk of these huge

structures can consist of mass concrete of rather low quality

provided the surface has the necessary qualities. A major constraint to the use of specially-tailored composite concrete members is the increased requirement for skilled manpower and the

fact that each new application has to be considered separately.

Close collaboration between materials engineers and structural

engineers is essential.

46
Use of Slags in Concrete

There is a high potential for energy saving through partial

substitution of ground granulated blastfurnace slags for portland cement in ready mixed and other concretes. In general, the

concrete mixes should be redesigned. At present, the exploitation of this potential saving is hindered by lack of suitable

granulated slags, lack of slag granulation plants, and lack of

education of the concrete community. Steps which should be

taken are the development of an educational program and a quality standard program, improvement of specifications and methods

of test, and investment in slag granulation facilities.

Recycled Concrete as Aggregate

Concrete prepared using recycled concrete as aggregate is

as workable as conventional concrete, has a compressive strength

of at least 70% of that of conventional concrete, and a modulus

of elasticity which is at least 60% of that of conventional

concrete. Other properties such as resistance to freezing and

thawing and volume stability are similar to those of conventional concrete. It is recommended that research be carried

out to develop additional data about how the various parameters, such as time and water-cement ratio, affect the strength

and durability properties of concretes containing recycled concrete aggregate and the sensitivity of mechanical properties to

the properties of the recycled concrete aggregate. It has been

established that, where recycling plants are competitive, energy

savings are realized in the form of savings of transportation

fuel. Specifically, for each hour of recycling plant operation,

a saving of 180 gallons of fuel is obtained. At present, there

are 15 recycling plants in operation while the market conditions

permit the profitable operation of an additional 50 plants. Assuming that the research mentioned would trigger the establishment of 50 additional plants, the fuel savings would be of the

order of 18 million gallons per year.

Fiber-Reinforced Cements and Concretes

The use of fiber-reinforced cements (FRC) and concretes

can, at least in some cases, aid in the reduction of energy

consumption on a construction project through (1) reducing the

quantity of cement needed, (2) reducing the product weight,

(3) eliminating or reducing the conventional reinforcement,

(4) reducing construction time, (5) increasing service life, and

(6) decreasing maintenance requirements. In precast products

such as pipe, architectural panels, and underground utility

boxes, the section thicknesses can be smaller because of the

superior flexural strength of glass or steel FRC. Energy

savings in production and transportation can result from the

reduced quantities of material required, the reduced product

47
weight, and the decreased dead load on structures. However, it

should be noted that the fibers are energy-intensive materials

such as steel, glass, and polypropylene, and the concrete mixes

are cement-rich. There are also advantages to the use of

shotcrete-applied FRC in slope stabilization. The FRC follows

the slope contours, there is no minimum thickness constraint,

no mesh is required, and the construction time is significantly

reduced. Similar considerations apply to the use of FRC shotcrete mining and tunneling applications. If the full performance potential of fiber-reinforced concrete could be achieved,

it is possible that the material costs in given applications

would be less than those for portland cement concretes. Further

development of the equipment required to handle fibers and

fibrous concretes is neededc

Autoclaved Calcium Silicates and Other Alternative Materials

for Concrete

Autoclaved calcium silicate products can be substituted

for portland cement concrete in some applications. These

include both dense products such as sand-lime block and less

dense ones such as aerated concrete. Autoclaved products may

also be reinforced. Other alternative products may be made

using lime-pozzolan mixtures and low-pressure steam-cured

lime-silica materials. Although such products and materials

will only save energy relative to concrete in areas where there

are favorable factors, the possibilities should not be overlooked. Restraints to the widespread use of autoclaved calcium

silicate products are (1) the fact that they can, in general,

only be used for precast work, (2) existing autoclave processes

are probably not energy-efficient, and (3) a significant capital

investment is required to establish a plant. Nevertheless, it

is recommended that studies be made of possibilities for the

use of autoclaved calcium silicate products and the institutional barriers to be overcome to exploit them. In particular,

the possibilities for the use of autoclaved aerated concrete

in regions where thermal insulation is important should be

investigated. It is possible that cements which are unsuitable

for normal use (e.g., cements which are high in MgO) could be

used.

Polymer- and Sulfur-Concretes

Polymers and sulfur can be used in concrete to produce concretes of improved performance. It should be possible to

reduce the overall energy costs associated with some structures

if the service life can be increased and if less material is

needed. Although it is known that great improvements in properties such as strength and durability can be achieved, it is

not yet possible to determine the life-cycle costs. Field

trials are urgently needed in applications such as structures,

48
p) Titanium Alloy Reinforcing Bars

The corrosion of steel reinforcement in waterfront structures leads to waste of materials and energy. The problems are

particularly severe in tropical locations where seawater has

to be used for mixing and where the only aggregates are corralline limestone. The durability and service life of such

structures could be increased many-fold if titanium alloys

instead of steel, were used for reinforcement. Reduced maintenance requirements would lead to a reduction in energy consumed

in repairing or replacing the structure. The unit mass of

titanium alloy is 44 percent less than that of steel, the thickness of concrete cover over titanium could be less than that

over steel, the working stresses in titanium-reinforced concrete

could be increased at least 100 percent over those for

steel-reinforced concrete so that micro-crack development

in the concrete cover would pose no problems, and the dead

weight per unit volume of titanium-reinforced concrete would be

appreciably less than that of steel-reinforced concrete. The

reduced cross-sectional areas of the structural components, the

correspondingly reduced dead weights, and the absence of spalling would compensate for the initially greater cost of the

titanium alloy reinforcing bars. A strict analytical study of

a concrete section reinforced with Ti-6A1-4V alloy is needed

to determine the effects of titanium reinforcement on the structural behavior of slabs and piles including stiffness, strength,

safety, ductility, and allowable working stresses. It would

also be necessary to survey titanium alloy producers to

ascertain the feasibility of commercial production of deformed

titanium alloy reinforcing bars for use in all future construction of commercial and governmental reinforced concrete waterfront structures.

6.5 Research Needs

a) Waste or By-Product Utilization

Designers have become very selective and wasteful in

choosing concrete materials. In part, this is due to the past

low cost of concrete materials which made it possible to justify

their selection on the basis that less inspection would be necessary. Today, the balance between labor and materials has

changed so that less costly materials should be used when feasible. The use of less costly waste and by-product materials

often contributes to energy conservation. A variety of waste

and by-product materials exists, primarily at the local level,

which can be used in concrete provided due care is excercised.

These include incinerator wastes, slags, ashes, ceramic wastes,

waste sludges, and building demolition products. Many of these

wastes could be incorporated in foundations or similar structural

49
uses of concretes. To facilitate their use, a guide book

for operators of concrete plants should be prepared. The

book should provide information on individual waste and

by-product materials and precautions required in their use.

Research which could provide the necessary data is underway at

the Bureau of Mines and the Federal Highway Administration but

large numbers of samples will need to be tested to develop

suitable guidelines. Other work is needed to identify the types

and quantities of materials available at the local level, particularly in areas which are short of aggregates.

Recycled Concrete as a Source of Cementitious Materials

The recycling of concrete as aggregate has been demonstrated. However, it has not been established whether the

hydrated portland cement in recycled concrete could be reused

as a cementitious material. Since it is likely that the dehydration of the hydrated cement could be accomplished at relatively low temperatures, it is recommended that the possibilities be investigated. The concept could be explored through

a modest reserch effort.

Fiber-Reinforced Concrete

Most fiber-reinforced concretes are made with fibers which

have no special provision for bonding or anchorage and which are

distributed more or less uniformly throughout the concrete. If

improved bonding or anchorage of the fibers could be obtained,

and if fiber distribution and orientation could be optimized

in areas of maximum tensile stress, wear or impact, performance

equal to the usual fiber-reinforced concretes could be obtained

with a much lower volume of fibers. A smaller quantity of

fibers would permit less cement paste to be used in the matrix

without loss of quality. Fiber contents for equivalent performance in many applications can be reduced by 75 percent and,

with the associated reductions possible in the cement content,

large reductions in energy requirements over conventional

fiber-reinforced concrete can be achieved. Research needs are

(1) determination of the bonding or anchorage of individual

fibers needed to provide maximum strength without loss of ductility, (2) development of practical means for orientation of

fibers, (3) determination of the mechanical behavior of

sectional members reinforced by fibers only in the areas of

maximum tensile stress, wear, or impact, (4) development of a

rational means for measuring toughness by which various

fiber-reinforced concretes can be compared, and (5) determination of those properties, other than strength and toughness,

which distinguish individual fiber-reinforced concretes from

plain concrete and how these properties should be measured.

50
d) Ferrocement

Ferrocement is a composite material consisting of a portland cement mortar reinforced with multiple, closely-spaced layers of reinforcement, such as wire mesh. This produces a relatively flexible, ductile concrete which lends itself to factory

production. However, further work is needed to make this system

competitive from an energy viewpoint and to provide information

on performance characteristics required for designing ferrocement structures. Development of construction techniques in

which the matrix is sprayed on to the preformed reinforcement

is needed. Among the benefits are the replacement of more

energy-intensive materials such as steel, the use of ferrocement

as formwork which can be left in place, and ability to tailor

systems to meet specific needs.

e) Polymer- or Sulfur-Modified Concrete

Within the last decade, much research has been devoted to

various kinds of polymer and sulfur concrete composites. Interest has been stimulated by the improvements obtained in properties such as strength, ductility, stiffness, impermeability,

and durability. More information is needed for potential users

who must assess the initial and long-term costs of these types

of concretes in relationship to performance in applications such

as highways and structures. Research should be carried out to

establish the cost-effectiveness and energy use requirements for

all principle types of polymer- and sulfur-containing concretes.

This should take into account (1) present and estimated lowest , future costs of production and processing, (2) present and

conceivable applications, (3) short and long-term performance

and reliability, and (4) cost and energy benefits in comparison

with conventional concrete, e.g., benefits of reduced maintenance costs.

f ) New Lightweight Aggregates

The use of lightweight aggregate concretes in tall structures reduces the loads on columns, thus allowing smaller

column sections. This results in savings in cement and energy.

At present, lightweight aggregates are produced by bloating

clays and shales in rotary or other kilns. With the increase

in oil and gas prices, the cost of producing lightweight aggregate has risen considerably. Alternative, lower cost methods

and materials are now needed for the production of lightweight

aggregates. Research is needed on the use of coal wastes as

sources of lightweight aggregate materials since the residual

fuel value of the waste could be exploited. Other systems

with potentials for energy savings should also be investigated.

51
g) Phase Change Materials

The storage of thermal energy at ambient temperatures is a central design feature of building structures which are to provide for optimal use of hybrid energy sources. These sources

include active and passive solar systems and off-peak electrical

energy. Methods for incorporating phase change materials in

concrete-based composites should be developed. Two methods

which should be evaluated are encapsulation and inclusion as

an emulsion. The effect of the phase change material on the

properties of the concrete should be investigated. It is estimated that the use of phase change materials could result in

savings of 50 percent of the heating and cooling costs of new

structures and about 30 percent in existing structures.

7. INSTITUTIONAL FACTORS

7.1 Background

Energy conservation in the cement and concrete industries is not a purely technical matter. Many institutional factors affect the generation, transfer and exploitation of the technical knowledge necessary

for energy conservation. Examples are the societal climate, the availability of capital, the tax structure, transportation subsidies and tariffs, the educational system, the standards system, support for research

and development, the technical information system, and environmental

legislation. It was the purpose of the working group to consider if

and how institutional factors might be employed to foster more efficient

use of energy in the cement and concrete industries.

7.2 List of Statements Prepared by the Working Group

Energy-Saving Opportunities:

a) Use of cements with inorganic residues and wastes

b) Increased use of fly ash in concrete

c) Academic programs in cement and concrete technology

d) Educational cement and concrete energy reviews

e) Cost sharing in technological innovation

Research Needs:

a) Implementation of workshop output

b) Joint university-industry R&D
c) Collection of data on energy use in the cement and concrete

system

d) Uniformity of specifications for cements

e) Performance acceptance testing

f) Mathematical model of the cement and concrete system

Unresolved Issues:

a) Adequacy of knowledge about raw materials reserves and

resources

b) Societal impact of using by-products in concrete

7.3 Summary of the Discussions

The working group on institutional factors spent much of its time

discussing general categories of institutional factors before turning its

attention to specific energy-saving opportunities, research needs, and

unresolved issues. This summary of its discussions is based on notes

submitted by the chairman and co-chairman after the close of the workshop. The group identified 5 energy-saving opportunities, 6 research

needs, and 2 unresolved isssues.

The working group decided to treat the institutional issues under

five headings:

Economics

Education

Technical Matters

Materials Conservation

Societal Matters

Economics was given first priority because the rate and extent of

implementation of energy conservation measures, and also the creation of

vehicles for development of the necessary technology, depend upon the

availability of sufficient capital. Education was given second priority, because sufficient knowledge must be made available for

implementation of any major energy conservation program. Broad educational programs are also a prerequisite for progress towards creation

of R&D-intensive cement and concrete industries capable of sustaining

their own technical development. The discussion of Technical Matters of

an institutional nature which impact directly on energy conservation concentrated on the standards system. Materials Conservation was discussed

53
because it was recognized that energy and materials conservation are

not always in harmony and may sometimes lead to conflict at the institutional level. Lastly, Societal Matters were discussed because of the

necessity of ensuring that any actions taken to meet societal needs are

understood by society.

International cooperation was recognized as an institutional factor

with important implications for energy conservation. For example, postwar conditions in Europe had required serious attention to be given to

energy conservation many years before the matter became crucial in the

U.S. and a wealth of experience had been gained. European participants

in the working group expressed their interest in cooperating on the

issues raised.

Economics

The primary economic issue is the availability of capital. A

report prepared by the Portland Cement Association (PCA) for the Federal

Energy Admins t rat ion* pointed out that the principal constraint to

adoption of the more significant long-term energy conservation measures

is the enormous requirements for investment capital. Estimates of the

capital requirements of the U.S. portland cement industry were given in

a PCA report submitted to the Cost of Living Council in March 1974.

Based on the PCA figures, but with modifications to reflect new

information, the total capital needs of the industry are estimated

to be:

(1) New capacity additions totaling 36 million

tons of annual capacity required by 1980 at

$70 per ton; (figures based on product demand

forecast by the Boston Consulting Group). $2.52 billion

(2) Conversion where practicable of existing

wet-process plants to more energy-efficient,

dry-process preheater methods; (49.5 million

tons at average conversion cost of $41 per

ton of capacity). 2.03

(3) Conversion of present plants utilizing

petroleum fuels exclusively to permit use

of coal; (39 million tons of capacity at

estimated conversion cost of $3.20 per ton). 0.13

(4) Capital expenditure to meet EPA 1975 standards

for air and water pollution control. 0.28

* "Energy Conservation Potential in the Cement Industry," FEA Conservation Paper No. 26 (1975) NTIS No. PB-245-159.

54
(5) Replacement of obsolete plants (more than

40 years old) with new energy-efficient

production facilities; (11 million tons at

1974-75 estimated of $70 per ton). 0.77

Total capital needs $5.73 billion

This figure, which is based on the industry's estimate of its

own needs, is for "up-dating" the U.S. cement industry to use energy

conservation technology already in use in other countries. The

additional capital needed for industrialization of cement use in

concrete, and for other means to conserve energy in the use of cement,

is not on record. We also lack estimates of the additional capital

which would be required for the U.S. cement and concrete enterprises to

gain international leadership comparable to that of U.S. construction

engineering.

The existence of legislative barriers which prevent invested

capital from offering reasonable ROI's (returns on investment) was

recognized; they hinder energy conservation efforts. Analytical studies

on this issue were suggested. It was also suggested that wider use

could be made of existing government support schemes for high-risk

development projects. A study of European programs for support of highrisk projects was recommended. It was also recommended that the views

expressed in the workshop should be brought to the attention of decision

makers concerned with economic matters.

Education

The need for various levels of education to improve the technical

knowledge base of the cement and concrete industries was discussed. It

was recognized that there is a need for strong basic and applied

research efforts to advance the cement and concrete industries, and

a need for a system for the flow of knowledge from basic research,

through development, into the commercial application and marketing of

technology. These subjects could benefically have been discussed

further. In the area of research management it was pointed out there

is much useful information available from other industries; reference

was made to studies of the Industrial Research Institute (IRI) and

the European Industrial Research Management Association (EIRMA). The

fragmentation of the cement and concrete industries, and of the relevant

research activities, was recognized as a barrier against development

of comprehensive research programs. The group agreed about the need

to remedy this. The use of government-sponsored schemes for joint

university-industry research was proposed as one way of strengthening

the technical basis of the cement and concrete industries. Examples

of European programs of this sort are those at Aston University in

England, and at the Academy of Technical Sciences in Denmark. It was

noted that studies of joint university-industry research activities had

been performed by both IRI and EIRMA. On another matter, it was recommended that research should be carried out to compile data on energy

consumption in the broad range of activities related to construction

55
including the manufacture of materials, construction, use of buildings,

transportation, etc.

Technical Matters

Two of the items discussed related to standards and specifications.

They encompassed a broad range of energy-related constraints. First, the

proliferation of specifications for hydraulic cements in the U.S. has

been an obstacle to standardization of products; it has caused waste of

energy and increased costs because of needs for additional storage and

handling. Recent cooperative efforts have resulted in much closer

conformity between ASTM and Federal Specifications, but there remains a divergence at state and local levels. Often, the differences in the

specifications are not based on sound technical considerations. The

Federal government could perform a valuable service by promoting uniformity of standards and specifications at all levels of government, and

giving consideration to existing international standards. Secondly, it

was suggested that use of performance acceptance testing should be

encouraged. Current ASTM, Federal and AASHTO specifications for hydraulic cements are an amalgam of prescriptive and performance specifications. Prescriptive specifications tend to stifle innovative developments and to be wasteful of energy and resources. Whenever possible,

prescriptive specifications should be replaced or supplemented by performance requirements. Where standard performance tests would not be practical for acceptance testing, because of the time factor, accelerated

tests should be devised to supplement standard long-term tests. Performance specifications could encourage innovation in low-energy product

development, and reduce the costs of manufacture and testing.

Materials Conservation

In the area of materials conservation, one of the most interesting

ideas discussed concerned the establishment of a computer model of the

cement and concrete manufacturing realm. This would enable simulations

to be performed to investigate the impacts upon energy use and system

economics of possible technological changes. The group felt this would

be a prolific field with significance for the making of decisions on

many levels including research and development, corporate operations,

and governmental planning and policy making. It was also suggested that

development of a comprehensive model would benefit from international

cooperation, and the group recommended that this should be noted. In

other discussions of materials conservation, a need for more knowledge

on material resources for cement and concrete manufactured in the U.S.

and their rates of depletion was pointed out. It was recognized that

increased use of by-products, notably fly ash and slags, in cement and

concrete could conserve energy and materials, and it was suggested that

improvements in the durability of concrete would also help conserve

energy.

56
Societal Matters

Although it did not propose any actions, the working group felt

that the social impact of energy conservation, and of advances in cement

and concrete technology, was obvious and that awareness of it should

be promoted by industry, government, and the science and technology

sector. Confidence in proposed actions must be won from the many segments of public opinion including politicians, students, and so forth,

if the large programs needed in the U.S. are to be undertaken.

7.4 Energy Saving Opportunities

a) Use of Cements with Inorganic Residues and Wastes

The ability of concretes to be made with a wide variety of

inorganic residues and wastes should be capitalized on. The

potential benefits are the use of low-cost resources and the

development of materials with unique performance characteristics. The constraints to the use of the residues and wastes

include a lack of coordinated knowledge regarding the available

residues and wastes and the lack of a comprehensive enterprising outlook which can cut across industry sectors. One way

of attempting to exploit the opportunities would be to establish programs in research institutes, or in joint activities

of businesses and universities, to identify and investigate

candidate systems and estimate the developmental requirements

and costs.

b) Increased Use of Fly Ash in Concrete

The amount of portland cement used in ready mixed and other

concrete could be reduced by redesigning the mixes to use fly

ash. It is recognized that care would have to be taken in

selecting fly ash to ensure quality and uniformity. A factor

to be taken into account is the lack of education of the

concrete community (e.g., specifying agencies, purchasers and

users) about the benefits of, and the technical requirements

for, the successful use of fly ash. Among the steps which could

be taken to promote increased use of fly ash in concrete would

be development of an educational and quality standard program

through cooperation between organizations such as the National

Ready Mixed Concrete Association and the National Ash Association. The educational program would have to cover mix

proportioning techniques and it would be essential for it to

be supported by high quality technical service to the user.

Other actions needed would be improvement of standard methods

of test and specifications for fly ash. The use of government

purchasing power could encourage increased use of fly ash in

concrete. The effects of the freight rate structure on the

competitiveness of fly ash may have to be taken into account.

57
Academic Programs in Cement and Concrete Technology

The optimum use of concrete material resources requires the

availability of well-trained technicians. It is recommended

that a full academic program be established at the university

level leading to one or more degrees in cement and concrete

technology. The program should cover cement chemistry, cement

manufacturing processes, aggregate production, and the manufacture and delivery of concrete. It is recognized that there

may be problems in generating student interest in such a program

and in finding a university with the capability and willingness

to undertake the program. There are also questions about the

cost of establishing a viable program and assuring a job market

for graduates. It is recommended that existing programs in foreign countries be reviewed and an industry committee be set up,

perhaps by the PCA, to seek a major university to undertake

establishment of the program, to guide curriculum development,

and to assure job opportunities for graduates.

Educational Cement and Concrete Energy Reviews

There is an urgent need to centralize and disseminate

energy information presently buried in miscellaneous publications, including untranslated articles. Because of the need for

education and the promulgation of ideas, it is recommended that

an educational quarterly or semi-annual cement and concrete

energy review be published. It would consist of domestic and

foreign articles on energy topics pertinent to the industry.

The energy-related topics would cover general information,

processes and equipment. It would also publish foreign translations (a current problem) and provide space for reader

contributions including an idea forum. Constraints in establishing the publication might be competition from existing publications and the difficulty of obtaining funds and finding

competent staff. Competent editing and selectivity in choosing

items for publication would be essential. If Department of

Energy funds were available, the review might be prepared by

the Department staff and published by the Department or through

a publishing house. An alternative might be to have it published under contract by an existing publication.

Cost Sharing in Technological Innovation

There is a need to stimulate technological innovations with

energy-conserving potential. Innovations might, for example,

relate to the use of process heat and the use of wastes and

by-products, and their development might require cooperation

between equipment manufacturers, raw material suppliers, cement

and concrete producers, and end users. Cooperation between the

industries might be encouraged if introduction and development

of technological innovations could be carried out on a shared

58
cost basis but, at present, it appears that cooperation is hindered by legal constraints and a lack of capital for joint developments. Among possibilities for stimulating technological

innovation which should be considered are establishment by the

industry of professional chairs in cement and concrete technology at some leading educational institutions, revitalization

of existing cement and concrete associations, and various forms

of government-industry interaction and government funding.

7.5 Research Needs

a) Implementation of Workshop Output

The study of energy conservation opportunities in the

cement industry which was sponsored by the Federal Energy Administration served to codify the state-of-the-art. The present

workshop documents the perceived need for new technology. It

is recommended that the suggestions received be ranked in order

of energy-saving potential and that high-potential projects be

scoped out with a designation as to who should fund them, e.g.,

the private sector or the government. This would be an essential step in the implementation of the workshop output.

b) Joint University-Industry R and D

The U.S. cement and concrete industry is fragmented both

horizontally (many cement companies) and vertically (cement

manufacturers, concrete producers, contractors, and customers).

This makes innovation difficult because carrying ideas from

exploratory research through development, production, and

marketing requires cooperation between successive stages of the

vertically-fragmented industry. Fragmentation also leads to

lack of research funding since no one segment expects to profit

sufficiently from an innovation to justify research expenditures. It appears that government encouragement may be required

to overcome the constraints to R and D. This might be through

new educational programs or direct sponsorship of universityindustry efforts to develop more energy-efficient cements,

concrete production, and construction techniques. It is recommended that a government-sponsored, university-industry internship program should be instituted to train new R and D personnel. Also, programs of this nature which have been undertaken

in Europe should be examined. Among the expected benefits would

be an increased supply of highly-motivated, well-trained, technically competent R and D personnel capable of producing real

innovation and successful market penetration for energy-saving

products and construction practices.

59
Collection of Data on Energy Use in the Cement and Concrete

System

If the highest benefit/cost ratio is to be achieved from

energy conservation activities, it is necessary to know where,

and how much, energy is being used. It is also necessary to

know which energy uses are most susceptible to reduction by

application of existing knowledge and by further research and

education. It is therefore recommended that a methodology for

computation of energy use be established and applied to data

which would be collected for various segments of the industry

and for various types of projects using concrete. The collection and analysis of the data might be done by industry orga

nizations, trade groups, graduate students in engineering or

economics, or a joint effort of industry and academe. Factors

to be considered would be mining of raw materials, cement

production, manufacturing of concrete, construction, transporta

tion, and the maintenance and operation of completed concrete

constructions. Secondary and tertiary effects would also have

to be considered such as the energy cost of manufacturing the

equipment that is used to transport, manufacture and construct

concrete facilities. The data collection would best be done

in a series of steps of limited scope and the results should

be subjected to peer review. The project might include a mathematical model and use statistical sampling techniques to guide

the field collection of data. The results would focus attentio

on areas using excessive amounts of energy and provide a rational method for designers and other users of concrete to reduce

energy consumption.

Uniformity of Specifications for Cements

The various specifying agencies have been working to bring

about closer conformity between their specifications. Recent

experience has demonstrated the value of this standardization i

helping both the producer and consumer use modern cement technology. It is recommended that the federal government promote

guidelines and standards for uniform specifications at all

levels of government such as state, county, etc. Such guidelines and standards should include consideration of existing

international standards. The benefits would be improved opportunities for exploitation of innovative developments such as

blended cements and admixtures; reductions in energy use; and

reduction of the costs of manufacture, storage, and laboratory

testing.

Performance Acceptance Testing

Current ASTM, Federal, AASHTO (American Association of

State Highway and Transportation Officials) and state specifications for hydraulic cements are an amalgam of prescriptive

60
and performance requirements. Efforts should be made to adopt

performance tests for acceptance whenever possible, with accelerated methods being used to supplement conventional long-term

tests in order to expedite earlier acceptance of products.

There is a need to expand our knowledge of performance tests,

accelerated tests, and the correlation between laboratory test

results and field experience. While the cost of the required

work is not known, the savings achieved would probably justify

the research effort. The benefits would be improved opportunities for exploitation of innovative developments such as

blended cements and admixtures; reductions in energy use;

and reduction of the costs of manufacture, storage, and laboratory testing.

Mathematical Model of the Cement and Concrete System

In the conversion of raw materials into concrete in service, many processes take place. The processes include quarrying, crushing, grinding, mixing, pyroprocessing, mixing of

concrete, placing of concrete, curing of concrete, and aging

of concrete in service. Enough is already known about many of

these processes to enable at least crude mathematical models

to be developed. If a comprehensive model (macro-model) of

the total system were developed, it would be valuable as an

educational tool, and a tool for decision makers to use in

studying the interrelationships between the diverse factors

in the cement and concrete system which affect energy use and

life-cycle performance. It is recommended that the mathematical

models which have already been developed and which could be

used in the development of a macro-model of the cement-concrete

system should be identified. This should be followed by

identification of additional models of portions of the system

which would need to be developed to complete at least a rudimentary macro-model in a form suitable for further development.

The model would be useful as an educational tool to help

students understand the complex technical relationships between

cement manufacture and cement performance in concrete; for

aiding assessment of the energy implications of changes in the

cement-making process and in other factors affecting the

life-cycle performance of concrete; for aiding economic decisions; and for identification of research needs. Overall, it

would help improve the education of our future decision makers

and improve the quality of decisions relating to energy and

materials conservation in the cement and concrete system. The

development could benefit from, and contribute to, international

cooperation.

61
7.6 Unresolved Issues

a) Adequacy of Knowledge about Raw Materials Reserves and Resources

There appears to be uncertainty as to whether there is adequate knowledge about reserves and resources of raw materials

used for the production of cement and of other materials needed

for the concrete industry. While the U. S. Geological Survey

and the Bureau of Mines publish data about material reserves

and use, it is not clear whether the figures are reliable and

whether they take into account possible changes in the needs

of the cement and concrete industries. If adequate knowledge

is not available, we may eventually discover we do not have

necessary materials in locations where they are needed (e.g.,

aggregates near urban centers). There is a question whether

requirements for low-alkali raw materials and low-magnesia

limestone are being considered in the projections for cementmaking materials. It is recommended that experts from the

cement and concrete industries review the status of the knowledge regarding the mineral resources needed by their

industries

.

b) Societal Impact of Using Wastes and By-Products in Concrete

There is uncertainty about the societal impact of using

wastes and by-products in concrete with the aim of conserving

energy, replacing depleted materials, and improving the energy

saving in housing, etc. There is a need to make sensible use

of wastes and by-products in order to save energy and materials,

and to dispose of environmentally objectionable materials.

Opposition, or lack of support, is due to lack of knowledge

regarding the opportunities and to some conflicting economic

considerations. In cooperation with governmental energy conservation agencies, the industry should explain the issue to

a broad public.

8. SUMMARY

The recommendations of the six working groups covered a broad range

of ideas for energy conservation. No attempt was made to rank the ideas

in order of importance. The range of opportunities for energy conservation in the cement and concrete industries can be appreciated by reviewing the ideas presented.

The largest direct use of energy in the manufacture of concrete

results from pyroprocessing to form portland cement clinker. Major oppo

tunities for energy conservation, therefore, lie in reducing the energy

requirement for the manufacture of clinker and in reducing the amount

of cement used in concrete. The latter may be accomplished by partial

replacement of cement by suitable waste or by-product materials or

62
through the more efficient use of concrete. Suggested opportunities

for reducing the amount of energy used in clinkering include the

following:

o use of fluxes to lower the reaction temperature in the kiln

o permit higher free lime contents of clinker

o improve the uniformity and the particle size distribution of

kiln feed

o select more reactive raw materials which will require less

energy for clinker formation

o recover more heat from kiln exit gases

o improve ability to predict heat transfer and chemical reactions

within the kiln.

Most of these items, like the others listed in this summary, imply

needs for research as well as opportunities for energy savings.

Methods proposed for using concrete more efficiently include:

o increase the use of blended cements containing fly ashes, granulated blastfurnace slags, or other suitable waste or by-products

o increase the use of water-reducing admixtures in concrete to

obtain strength benefits

o avoid overdesign by tailoring concrete properties to meet

the needs of the application and by manufacturing concrete of

greater uniformity

o develop more performance-oriented specifications

o develop improved tests for evaluation of performance of

concrete and concrete constituents.

Although most of the energy used in the manufacture of cement is

consumed in pyroprocessing, substantial amounts are also used in other

processes. The grinding of the cement-making raw materials and the

grinding of the clinker to make cement use large quantities of electrical

energy. The inefficiency of grinding processes indicates that there are

possibilities for improvement. Examples of suggestions for improving

grinding efficiencies are:

o investigate factors affecting the dispersion of powdered

materials in mill systems

63
o carry out an impartial evaluation of particle size classifiers

and disseminate the results

o investigate the possibilities for improving the grindability of

clinker through control of kiln and clinker cooler

o pretreat raw materials to improve their grindability

o select raw materials which require less energy for preparation.

The energy consumed in cement manufacture is also affected by the

degree of control exercised on the manufacturing processes. For this

reason, methods for the rapid and reliable analysis of raw materials

and clinker are needed. Two specific suggestions concerning analysis

were:

o develop a range of standard reference materials suitable for

checking analytical procedures and calibrating analytical

instruments

o develop improved methods for determining the quality of clinke

Many operations in the manufacture and transportation of concrete

offer potential for energy savings. Among the suggestions made were:

o remove unnecessary requirements for the curing of concrete

o carry out energy audits of concrete manufacturing plants

o develop storage and handling procedures to help retain the

natural heat in concrete constituents

o use recycled concrete as aggregate in new concrete

o improve test methods and production control

o transfer more information from cement producer to cement user

o optimize the transportation network.

Although many technical opportunities for energy conservation were

identified, it was apparent that there were serious institutional barriers to exploitation of the opportunities. These included availability

of capital, education, technology transfer, standards and codes. Among

the actions needed to remove barriers to, or provide incentives for,

exploitation of opportunities for energy conservation were:

o provide training for cement and concrete technologists

o remove unnecessary restraints to use of innovative materials

posed by prescriptive specifications

64
o provide government support or incentives for research and

development

o identify capital requirements for exploitation of energy-saving

opportunities

o promote dissemination of information on opportunities for

energy conservation through cement and concrete technology

o stimulate cost-sharing in technological innovation

o stimulate joint university-industry R and D

o develop a mathematical model of the cement and concrete system.

The workshop produced a large variety of suggestions concerning the

possible contributions of cement and concrete technology to energy conservation. The list of suggestions, though long, is undoubtedly incomplete. Nevertheless, it should draw attention to energy-saving opportunities for immediate implementation and suggest profitable areas of

research. One of the suggestions made at the workshop was that the

actions suggested should be implemented. The publication of this report

is a step in this direction. It is hoped that further steps will be

taken by its readers.

9. ACKNOWLEDGMENTS

By publication of this report we wish to acknowledge the contributions of all who participated in the Workshop and made the effort worthwhile. Their names are given in Appendix II. Particular thanks are

due to the members of the Steering Committee and the Chairmen of the

working groups (Appendix I) and to the following persons who, though not

able to attend the Workshop, wrote in to contribute ideas for discussion:

Harold Vivian, CSIRO, Australia; Stephen Gottlieb, Gorresen's Pty. Ltd.,

Australia; and Peter Hawkins, California Portland Cement Company.

We also wish to acknowledge the efforts of the many members of staff

of the National Bureau of Standards who helped with the organization of

the Workshop and assisted during the Workshop to make it run smoothly.

These include Sara Torrence, Lynn Boggs, Anita Sweigert, Marie Dickey,

Frank Davis and Nat Waters.

Last, we wish to acknowledge the support from the Division of

Industrial Energy Conservation, Office of the Assistant Secretary for

Conservation and Solar Applications, Department of Energy, which made

the Workshop possible.

65
APPENDIX I

Workshop Steering Committee and Working Group Chairmen

Steering Committee

Jerome Collins, Department of Energy

Geoffrey Frohnsdorf f

, National Bureau of Standards, Chairman

Richard Gaynor, National Ready Mixed Concrete Association

Roy Grancher, Rock Products Magazine

Nathan Greening, Portland Cement Association

Robert Philleo, Office of Chief of Engineers, U.S. Army

John Wachtman, Jr. , National Bureau of Standards

Working Group Chairmen

Group 1, Cement Production: Stewart Tresouthick, Universal Atlas Cement

Group 2, Cement Composition: Nathan Greening, Portland Cement Association

Group 3, Blending Materials: Francis Young, University of Illinois

Group 4, Concrete Production: Paul Klieger, Portland Cement Association

Group 5, Efficient Use of Concrete: Robert Philleo, Office of Chief of

Engineers, U.S. Army

Group 6, Institutional Factors: Gunnar Idorn, Aalborg Portland Cement,

Denmark

Louis Spellmann, Atlantic Cement (cochairman)

66
APPENDIX II

Workshop Participants

Jack Aellen, U.S. Department of Energy, Washington, D.C.

Gene Aleshin, IIT Research Institute, Chicago, Illinois

Arthur Anderson, ABAM Engineers, Inc., Tacoma, Washington

Richard Berger, University of Illinois, Urbana, Illinois

E. E. Berry, Centre for Mineral and Energy Technology, Ottawa, Canada

Russell Brink, Consultant, McLean, Virginia

Paul W. Brown, National Bureau of Standards, Washington, D.C.

Herbert Busching, National Bureau of Standards, Washington, D.C.

C. Crossett, Portland Cement Association, Charlottesville, Virginia

Jerry Clendenning, Ontario Hydro Research Laboratory, Toronto, Canada

James R. Clifton, National Bureau of Standards, Washington, D.C.

Jerome Collins, U. S. Department of Energy, Washington, D.C.

Frank Dall, Boiling Air Force Base, Washington, D.C.

Charles Dandois, Allis Chalmers Corp., Milwaukee, Wisconsin

Kenneth Daugherty, North Texas State University, Denton, Texas

Sidney Diamond, Purdue University, West Lafayette, Indiana

Pierre Dutron, CEMBUREAU, Paris, France

George Economos, National Academy of Sciences, Washington, D.C.

Bernard Erlin, Erlin, Hime Associates, Inc., Northbrook, Illinois

John Faber, National Ash Association, Washington, D.C.

Emery Farkas, W. R. Grace & Co, Cambridge, Massachusetts

Russell Fling, R. S. Fling & Partners, Inc., Columbus, Ohio

Geoffrey Frohnsdorff, National Bureau of Standards, Washington, D.C.

Stamatia Frondistou-Yannas , Massachusetts Institute of Technology,

Cambridge, Massachusetts

E. Fuller, National Bureau of Standards, Washington, D. C.

Hoke Garrett, Kaiser Engineers, Inc., Oakland, California

Richard Gaynor, National Ready Mixed Concrete Association, Silver Spring,

Maryland

Kenneth Gee, Bethlehem Steel, Bethlehem, Pennsylvania

Nathan Greening, Portland Cement Association, Skokie, Illinois

Woodrow Halstead, Virginia Highway Research Council, Charlottesville,

Virginia

Eric Hansen, Marquette Cement Manufacturing Company, Nashville, Tennessee

Edward Harboe, U.S. Bureau of Reclamation, Denver, Colorado

Karl Hauser, Edward C. Levy Co., Dearborn, Michigan

James T. Houston, Gifford-Hill & Co., Inc., Dallas, Texas

John Hurt, U.S. Army Research Office, Research Triangle Park,

North Carolina

Edward Hyland, Chicago Fly Ash Company, Chicago, Illinois

Gunnar Idorn, Aalborg Portland, Copenhagen, Denmark

Brad Inman, Charles Pankow, Inc., San Francisco, California

Vagn Johansen, F.L. Smidth & Co., Copenhagen, Denmark

James R. Jones, Environmental Engineering Corp., Houston, Texas

Clyde Kesler, University of Illinois, Urbana, Illinois

Waldemar Klemm, Martin-Marietta Laboratories, Baltimore, Maryland

Paul Klieger, Portland Cement Association, Skokie, IllinoisX

67
Participants (continued)

R. W. Kriner, Lehigh Portland Cement Co., Allentown, Pennsylvania

Lawrence Kukacka, Brookhaven National Laboratory, Upton, New York

E. M. Kulesza, Medusa Cement Company, Cleveland, Ohio

Ralph Lane, Tennessee Valley Authority, Louisville, Tennessee

David R. Lankard, Battelle-Columbus Laboratories, Columbus, Ohio

Donald W. Lewis, National Slag Association, Alexandria, Virginia

M. A. Lombard, The Lombard Company, Alsip (Chicago), Illinois

William R. Lorman, Naval Construction Battalion Center, Port Hueneme,

California

C. E. Lovewell, Santee Portland Cement Corp., Holly Hill, South Carolina

Edward P. Lynch, Argonne National Laboratory, Argonne, Illinois

Mohan Malhotra, CANMET, Ottawa, Canada

Jack Mander, Martin-Marietta Cement Technical Center, Baltimore, Maryland

John Manson, Lehigh University, Bethlehem, Pennsylvania

Irwin Margiloff, Scientific Design Company, Inc., New York, New York

Robert Massey, U.S. Department of Energy, Washington, D.C.

Robert McCallin, Marquette Cement Manufacturing Company, Silver Spring,

Ma ryland

Walter McCoy, Master Builders, Cleveland, Ohio

P. K. Mehta, University of California, Berkeley, California

Ronald H. Mills, University of Toronto, Toronto, Canada

L. John Minnick, Industrial Research Consultant, Plymouth Meeting,

Pennsylvania

Robert Morrison, Western Ash Company, Phoenix, Arizona

Howard Newlon, Jr., Virginia Highway Research Council, Charlottesville,

Virginia

Kenneth Newman, British Ready Mixed Concrete Association, Shepperton,

England

Lewis Newman, Federal Energy Administration, Washington, D.C.

Thomas Pasko, Federal Highway Administration, Washington, D.C.

Donald Pfeifer, Wiss, Janney, Elstner, Northbrook, Illinois

Robert Philleo, Office, Chief of Engineers, U. S. Army, Washington, D.C.

Robert Price, Interpace Corp., Wharton, New Jersey

Thomas Redmond, National Concrete Masonry Association, McLean, Virginia

Robert Reeber, U.S. Department of Energy, Washington, D.C.

Carl Robbins, National Bureau of Standards, Washington, D.C.

Delia Roy, Pennsylvania State University, University Park, Pennsylvania

W. G. Ryan, Blue Metals Industries, Ltd., Sydney, Australia

Peter Sereda, National Research Council of Canada, Ottawa, Canada

Raymond Schutz, Sika Chemical Corp., Lyndhurst, New Jersey

Jan Skalny, Martin-Marietta Laboratories, Baltimore, Maryland

George Snyder, Dravo Corp., Pittsburgh, Pennsylvania

Lewis Spellman, Atlantic Cement Co., Ltd. Stamford, Connecticut

H.F.W. Taylor, University of Aberdeen, Old Aberdeen, Scotland

Stewart Tresouthick, U.S. Steel Corp., Gary, Indiana

Rudolph Valore, Jr., Valore Research Associates, Ridgewood, New Jersey

John Wachtman, Jr., National Bureau of Standards, Washington, D.C.

68
Participants (continued)

Jimmy Walker, United States Gypsum Co., Des Plaines, Illinois

Birger Warris, Ceraenta AB, Malmo, Sweden

John Wilson, Martin-Marietta Cement Corp., Bethesda, Maryland

Norman Wingard, U.S. Bureau of Mines, Washington, D.C.

F. H. Wittmann, Delft University of Technology, Delft, Netherlands

K. Wood, Slagment Limited, Johannesburg, South Africa

Harvey Yakowitz, National Bureau of Standards, Washington, D.C.

J. Francis Young, University of British Columbia, Vancouver, Canada

Ronald Zollo, The University of Miami, Coral Gables, Florida

69
NBS-114A (REV. B-78)

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1. PUBLICATION OR REPORT NO. NBS SP 542

2.

4. title AND subtitle Possible Contributions of Cement and

Concrete Technology to Energy Conservation

Summary of the NBS /DOE Workshop held at the

National Bureau of Standards, Gaithersburg, MD

5. Publication Date May 1979

6. Performing Organization Code

7. AUTHOR(S)

Edited by Geoffrey Frohnsdorff , Paul W. Brown , James R.

J J Clifton

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

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16. ABSTRACT (A 200-word or.less tactual summary oi most significant information. If document includes a significant bibliography or

literature survey, mention it here.)

A workshop on Possible Contributions of Cement and Concrete Technology to

Energy Conservation by the Year 2000 was held at the National Bureau of

Standards on October 3 and 4, 1977. The purpose of the workshop was to identif

and record ideas on possible contributions of cement and concrete:- technology

to energy conservation in the near term and by the Year 2000. This included

consideration of current technology as well as areas in which technological

advances might be realized.

The workshop was divided into working groups on cement composition, cement

production, blending materials, concrete production, efficient use of concrete,

and institutional factors. The essential results from the six working groups

were statements of Energy-Saving Opportunities, Research Needs, and Unresolved

Issues. The statements, which are the major part of this report, are

presented without critical analysis. They suggest, however, that there are

a large number of possible opportunities which should be evaluated for their

ability to contribute to energy conservation in the cement and concrete

industries

.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Cement; concrete; research needs; energy saving- opportunities.

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