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THE EFFECTS OF WASTE GLASS AGGREGATE
ON THE
STRENGTH AND DURABILITY
OF
PORTLAND CEMENT CONCRETE
BY
Craig Polley
A thesis submitted in partial fulfillment of
the requirements for the degree of
Master of Science
Civil and Environmental Engineering
(Structures)
Department of Civil and Environmental Engineering
University of Wisconsin - Madison
1996
ACKNOWLEDGMENTS
I extend my thanks to my advisor Dr. Steven M. Crarner, Associate Professor of Civil and
Environmental Engineering; he has provided invaluable guidance and support throughout these
two years. The energy and attention which he afforded to this research and the interest which has
taken in my professional development are deeply appreciated.
Acknowledgment is extended to Dr. Rodolfo V. de la Cruz, Associate Professor of Materials
Science and Engineering for h ~ s support of the project.
F i c i a l support of the project fi-om the University of Wisconsin Solid Waste Research Council,
the Dane County Department of Public Works, the Wisconsin Department of Natural Resources,
and the United States Enviromntal Protection Agency is gratefully acknowledged. The
direction, interest, and assistance of John Reindl, Recycling Manager for the Dane County
Department of Public Works, is appreciated.
The following contributions are also deeply appreciated:
John Dunn, Dane County Public Works Engineer for technical assistance and coordination of
the field trials
The workers at Joe Daniels, Inc. for their patience during the painstaking construction of the
field trial sections
M. J. Schmidt Corp. of Milwaukee for their donation of waste glass
LaFarge Corporation and Holnarn Cement Corporation for their donation of portland cement
Wisconsin Power & Light and Wisconsin Electric Power Company for their donations of fly
ash
Lycon, Inc. for their donation of aggregates
W. R. Grace, Inc. for their donation of admixtures
Dr. Alex Mishulovich of Construction Technology Laboratory for processing the powdered
glass
For their guidance and help throughout my Master of Science program and before, I thank
Prof. Jok A. Pinchiera, Prof. Michael G. Oliva, and Prof. J e k y S. Russell.
Invaluable laboratory assistance was received from Bill Lang; and the research would not have
been executed without the help of my student colleagues and predecessors: Paul Bakke, Andrea
Carpenter, Kamili Jackson, Carolyn Knight, John Reigel, Dipal Vimawala, and Stephen Gaudette.
Special heartfelt thanks is due to my family, to my mother and father, for their unfailing love and
support, and to my wife, Thekla, a valued liiend and companion.
Craig Polley
Waste glass has been heavily targeted for recycling efforts by various municipalities. Not all waste
glass can be recycled into new glass, however, and alternative methods must be found for
utilization of this waste glass; one possible use for this glass is as aggregate in portland cement
concrete.
An experimental research program was conducted to identlfy characteristics of waste glass that
produce satisfactory concrete for pavement applications, to document the alkah-silica reactivity
(ASR) of waste glass aggregate and determine means of mitigating this ASR, and to determine the
effects of waste glass aggregate and powdered waste glass on the strength and durability of
concrete. The performance of waste glass/fly ash concrete was evaluated, and experimental work
conducted by the author, results of others at the University of Wisconsin, and other researchers'
pubhhed results were used to synthesize conclusions about the processes and m e c b m s of ASR
and strength development in waste glass/fly ash concrete.
The research was conducted in several distinct phases: a study of the interaction of coarse and fine
glass with fly ash and their effect on strength and durability, a field trial to study several of the most
promising mixes under field conditions, a laboratory test of the possible use of finely ground glass
as a cement supplement, and a series of accelerated ASR expansion mortar bar tests. Evaluation
of the experimental mixes included consideration of compressive strength, fr-eezdthaw resistance,
and resistance to ASR deterioration at ages fiom one month to three years. Some study of the
interactions between the experimental materials and air-entraining admixtures, water-reducing
admixtures, fly ash and fine powdered waste glass was included to aid application of the
conclusions to pavement trials.
It w& determined that the effects of glass aggregate on strength may be divided into three separate
effects: (1) water demand of glass aggregate; (2) interaction with strength developmnt by fly ash;
and (3) intrinsic effects of glass aggregate, including particle strength and paste-aggregate. bond.
The combined effect may range between an 80% loss in strength and a slight (=I% - 5%) gain in
strength as compared to the control, dependmg on the form and gradation of the glass and the type
of cemnt used. Freeze-thaw durability was found to be promising; ASR is demonstrated,
mitigation can be provided by judicious use of fly ash.
CHAPTER 3 - METHODS AND MATERIALS
MATERIALS AGGREGATES - CEMENTS, FLY ASHES AND POWDERED GLASS - CHEMICAL ADMUC~URE~
S'IRENGIH AND S'IRENGTH D ~ P M E N T STRENGTH OVERVIEW - Low-ALKALI MIXES - STRENGTH OVERVIEW - MODERATE- ALKALIMIXES - 0n-m O B S E R V A ~ N S - DEVELOPMENT OF STRENGTH - Low- ALKALI MIXES - DEVELOPMENT OF STRENGTH - MODERATE-ALKALI MIXES - RELATION TO GLASS CONTENT AND FORM - RELATION TO FLY ASH CONTENT AND
FORM - RELATION TO POWDERED GLASS CONTENT
&KALI-SILICA ~EACTIVITY AND D U R A B ~ OVERVIEW OF CON^ PRISM EXPANSION AND RELAn0N TO &SS C O m AND - ACCELERATED ASR SERIES RESULTS
vii
CHAPTER 5 - ANALYSIS OF DATA AND DISCUSSION
EFFECTS OF GLASS AGGREGATE STRENGTH - CAUSES OF STRENGTH REDUCTION AND VARIATION - DURABILITY - EFFEC~SOFFLY ASH - BEHAVIOR DURING PROCESSING AND IN FRESH CON^ AND WATER DEMAND - EFFECTS OF PARTICLE SHAPE AND TJXWRE - EFSXTS OF
GLASS AGGREGATE GRADATION - E m s OF POWDERED GLASS
E m OF IN-IERA~ONS BETWFEN MATERIALS EFFEIXS OF INTERACTIONS WITH GLASS ON BEHAVIOR OF RY ASH - hIERACTI0NS
WITH AIR-ENTRAINING ADMIXTURE AND WATER REDUCER
~KALI-SILICA REACTVlTY AND GATI ION R E A ~ Y - TE~~IMUMBEHAVIOR - EFFECrs OF FLY ASH ON ASR - M~GATION
RECOMMENDA~ONS OPTIMAL PROPORTIONS OF WASTE GLASS AGGREGATE AND FLY ASH - USE OF WASTE G~ASSAGGREGATE - USE OF MINERAL ADMIXTUFW IN W m GLASS AGGREGATE CON^ - ASR TBTPROCEDURES - AREASREQUIRINGFURTHERRESEARCH
CHAPTER 6 - SUMMARY, CONCLUSIONS AND RECOMMENDATIONS M)R APPLICATION
CONCLUSIONS STRENGTH - DURABILITY - ASR R E A ~ Y - E m a s OF POWDERED GLASS - ~ S O F F L Y A S H
APPENDICES APPENDIX 3.1
APPENDIX 3.3
APPENDIX 4.1
APPENDIX 4.2
APPENDIX 4.3
APPENDIX 4.4
APPENDIX 4.5
APPENDIX 4.6
VARIABLE PARAMEIERS OF THE A C C E L E R A ~ ASR EXPANSION MORTAR MIXES
COMPRES~IVE s m m RESULTS
CONCREIE PRISM ASR EXPANSION RESULTS
FREmEmAwRESULTS
ACC-W ASR EXPANSION RESULTS
PHOTOMICROGRAPH OF GLASS AGGREGATE, D - 0.6 MM
TRPAR'lTIE COMPOS~ON mMIS OF THE SYSTEMS CAO-AL~O~-SIO~ AND CAO-NA20,-S102
GRADATION OF NATURALGRAVELS A AND B, COARSE GLASSES CA, CB, CC, CD AND CE
GRADATION OF NATURAL SANDS A AND B, ACCELERATED GRADATION, FINE GLASSES FA, FB, FC, FD AND FE
GRADATION OF NATURAL SANDS A AND B, FINE GLASSES FF, FG, FH, Fl ANDFJ
WATER DEMAND BY GLASS AGGREGATE CONTENT
WA'IER DEMAND BY ASH CONTENT
WATER DEMAND BY POWDERED GLASS CONTENT
S'IRENGTH OVERVIEW - LOW-ALKALI CEhlENT- 28 DAYS
S'IRENGIH OVERVIEW - LOW-ALKALd CEMENT- 90 DAYS
STRENGTH OVERVIEW - LOW-ALKAU CEMENT - 1 80 DAYS
S-GTH OVERVIEW - M O D E R A T E - w CEMENT- 28 DAYS
SlRENGTH OVERVIEW - MODERATE-ALKALI CECbENT - 180 DAYS
D m ~ m OF STRENGTH - Low-ALKAU CEMENT - PINE GLASS GRADATIONS
DWPMENT OF S'IRENGlH - LOW-ALKALI CEMENT - COARSE GLASS GRADAlIONS
DEVELOPMENT OF S m m - POWDERED GLASS SERIES
D ~ P M E N T O F S m m - MODERATE-ALKALI CEMENT- No GLASS
D ~ P M E N T O F S m m - MODERATE-ALKALI CEMENT- 48% GLASS
DWFWENT OF S'IRENGIH - MODERATE-- CEMENT - GLASS
RELATION OF STRENGTH TO GLASS CON'IENT AND FORM
RELATION OF S~~ TO h H CONTENT AND FORM
--THAW STIFFNESS DEGRADATION - COARSE GLASS
GRADATIONS
FkEEE-THAW STIFFNESS DEGRADATION - FINE GLASS
GRADATIONS
FREEZE-THAW WEIGHT DEGRADATION - COARSE GLASS
GRADATIONS
FREEE$THAW WEIGHT DEGRADATION - RNE GLASS GRADATIONS
FkEEZE-THAW S-S DEGRADATION - FIEIl> TRIAL
--THAW STIFFNESS DEGRADATION - POWDERED GLASS SERIES
STIFFNESS LOSS BEIWEEN 10 AND 350 C Y C ~ BY POWDERED GLASS
CONTENT
CONCRE-IE PRISM EXPANSION BY GLASS CONTENT- 28 DAYS
CONCRE-IE PRISM EXPANSION BY GLASS CONTENT - 365 DAYS
CONCRE-IE PRISM EXPANSION BY GLASS CONTENT - 730 DAYS
CONCRETE PRISM EXPANSION BY GLASS CONTENT - 1095 DAYS
ACCELERATED ASR EXPANSION - GLASS WlTH N O W G A T I O N
ACCELERATED ASR EXPANSION - FLY ASHES F2 AND F3, POWDERED GLASS
RELITION OF S'IRENGT'H TO ASH CONTENT - MODFRATE ALKAI-J
MrxEs
A I R - E m AD- REQUIRED BY TYPE AND CONTENT OF GLASS AGGREGATE
AIR-E- AD- REQUIRED BY TYPE AND CONTENT OF FLY ASH
AIR--AD- REQUIRED BY C0NlENT OF POWDERED GLASS
WA'IER DEMAND WITH AND WlTHOUTHRWR BY GLASS CONlENT
RELATION OF CONCREIE EXPANSION TO FLY ASH CONTENT
GRADATTONS OF CEMENTS, FLY ASHES, AND POWDERED GLASS
AGGREGATE SPECIFIC G R A ~ AND ABSORBTIONS
GLASS AGGREGATE S ~ ~ ~ M A R Y D E S C ~ O N S
ASTM C6 18 CLAssrnc~no~ PARAME~FRS
SUMMARY OF ME DESIGN SPEC~CATIONS
ASR PER~RMANCE AT 28 DAYS
ASR PERFORMANCE AT 365 DAYS
ASR PERFORMANCE AT 730 DAYS
ASR PERFORMANCE AT 1095 DAYS
COMPONENTS OF STRENGTH EFl3m-S
STRENGIHS WlTH WASHED VS. UNWASHED GLASS AGGREGATE
CEMENT AND POWDERED GLASS Chmxnmsncs
FLY ASH C H A R A ~ S ' I I C S
V ~ L E PARAMEIERS OF THE GLASS-FLY ASH SERJES
VAFUABLEPARAMEIERSOF'~-IEFIEIDTRIAL
VAR~ABLE P- OF THE POWDERED GLASS SERIES
VARIABLE PARAME~ERS OF THE ACCEURA'IED ASR EXPANSION SERE3
GLASS-FLY ASH SERIES MIX AND FRESH CONCRE~E RESULTS
FED TRIAL MIX AND FRESH CONCREIE RESULTS
POWDERFD GLASS SERIES MIX AND FRESH C O N C R . RESULTS
GLASS-FLY ASH SERIES COMPRESSIVE STRENGTH RESum
FIElD TRIAL COMPRESSIVE STRENGTH RESULTS
J?ED TRIAL CORE STRENGTH RESULTS
POWDERED GLASS SERIES COMPRESSIVE S'IRENGIH RESULTS
FIElD TRIAL TENSILE S'IRENGIH RESULTS
POWDERED GLASS SEIUES TENSILE STRENGIH RESULTS
GLASS-FLY ASH SERIES CONCREIE PRISM ASR EXPANSION RESULTS
FIELD TRIAL CONCREIE PRISM ASR EXPANSION RESULTS
STIFFNESS RETAINED BY GLASS-FLY ASH SERIES DURING F/'T TESTING
A4.5.4 WEIGHT RETAINED BY FIEID TRIAL DURING F/I' TESTING 155
A4.5.5 STIFFNESS RETAJNFDBY POWDERED GLASS SERIES DURING F/T 156 T E S ~ G
A4.5.6 WEIGHT RETAINED BY POWDERED GLASS R ERIES DURING FJr TESIWG 156
A4.6.1 ACCELERAm ASR EXPANSION RESULTS 157
xiv
Cement Chemists' Notation - used throughout thesis
C CaO (calcium oxide; lime)
Si02 (silicon dioxide; silica)
A1203 (aluminum oxide; alumina)
F F%03 (femc oxide)
Glass Asmegate Stocks
CA
CB
cc CD
CE
FA
FB
FC
H20 (water; hydrate)
SO3 (sulfur trioxide; sulfate)
C02 (carbon dioxide; carbonate)
Washed, First Shipment of Coarse Glass
Unwashed form of Glass CA
Washed, Second Shlpment of Coarse Glass
Washed, Blend of Glasses CC and CE
Washed, Third Shipmnt of Coarse Glass
Washed, First Shipment of Fine Glass
Unwashed form of Glass FA
Washed, Second Shlpmnt of Fine Glass
Washed, Gradation #1 Ground in Laboratory fiom Glass FC
Washed, Gradation #2 Ground in Laboratory fiom Glass FC
Unwashed form of Glass FG
Washed, First Shipment of P8 Fine Glass
Washed, Glass FG with P50 fiaction discarded
Washed, Second Shlpment of P8 Fine Glass
Washed, limited, standardized -on of Fine Glass for use in Accelerated ASR Series
D
wlc
W/(C +n Na20e
R; R+; R20
CSH .
xO/o/y%, e-g., 20%/25%
man particle size of a particular aggregate fiaction (diameter)
the ratio water:cemnt by weight
the ratio water:(cemnt + tly ash) by weight
equivalent normality of Na20 = [Na20] + 0.658[K20]
generic notation for an alkali mtal or alkali oxide; generally either Na or K (or Na20 or K20)
the ratio CaO:Si02 in a particular CSnH gel i.e., C:S is equal to the coefficient x in the stoichiomtric expression
shorthand for CSmH gel
the quantities of glass aggregate and fly ash used in a particular mix, e.g., 20%/25% indicates that 20% of the total aggregate is replaced by glass aggregate, while 25% of the total cemntitious materials is £ly ash
the combition of coarse and fine glass aggregate used in a particular mix, e.g., C A K indcates that Glass CA was used to replace a portion of the coarse aggregate, while Glass FC was used to replace a portion of the fine aggregate.
OOEb indicates that only fine aggregate was replaced with glass, e.g., OOEG indicates that no coarse glass was used, while Glass FG was used to replace a portion of the fine %gregate.
A problem receiving increasing attention in the United States is disposal of solid waste, and among
the most popular methods of dealing with this problem is recychg. Waste glass has been heavily
targeted for recycling efforts; for example, proposals within the Wisconsin state legislature would
prohibit the disposal of glass containers in landfills and incinerators if enacted (1989 Wisconsin Act
335). Not all waste glass can be recycled into new glass for several reasons. Several reasons for
this include impurities which are chflicult to remove, prohibitive shipping costs to glass
manufacturing plants, or mixed color waste streams which are difficult to separate into useful raw
glass stocks. The amount of glass requiring disposal continues to grow, amounting to 13.2 million
tons in 1990. Of this amount, only 2.6 million tons, about 20%, was successfully recycled (U. S.
Dept. of Commerce 1993). Alternative methods must be found for utilization of this waste glass.
Of the possible alternative uses for this glass, recycling into construction materials is among the
most attractive because of the large volu~ne of material involved, the capacity for bulk use in the
construction industry, and the likely ability of construction applications to afford allowances for
slight variation in composition or f o m Such use of waste glass has been previously studied with
regard to asphalt and fWbase course material.
The use of glass as aggregate in portland cement concrete has been studied by a number of other
researchers (Figg 198 1; Johnston 1974; Schmidt and Saia 1963) - studying the mechanical
properties of the resulting concrete and investigating the alkali-silica reaction (ASR). Their
findings may be summarized as follows:
In many cases, the use of glass aggregate produces highly unsatisfactory concrete due to ASR
and poor strength developmnt (Johnston 1974); though this depends on the type of glass
aggregate used (Schmidt and Saia 1963). The most reactive glasses have a high content of
either boron or alkali oxides (Figg 198 1).
The compositions of various types and colors of container glass vary greatly, and have
substantial effects on their reactivities in concrete. S o n types of glass are able to supply
sufficient quantities of both silica and alkalis for a deleterious reaction to take place, with the
concrete matrix only acting as a solution medium (Figg 1981).
Below a critical value of cement content and equivalent alkali content, glass aggregate may
perform satisfactorily; but the critical value for a particular glass aggregate would have to
be determined by test (Johnston 1974).
Replacement of cement by 25% to 30% fly ash by weight appears to be an effective means
of ensuring satisfactory performance. Johnston suggests that the minimum amount of fly
ash required for a given case might depend upon cement alkali equivalent, cement content,
and the chemical composition of the glass and fly ash.
Using only a small proportion of glass aggregate does not adequately limit ASR
development if no other measures are used to control the reaction (Johnston 1974).
Concrete with a mixture of frne and coarse crushed glass exhibits slightly smaller
expansion than a concrete with only coarse crushed glass (Johnston 1974). ASR involving
glass aggregate is qualitatively different from ASR involving more porous natural
aggregates, exhibiting a pessimum relationship for particle size (Figg 1981).
The amount of expansion associated with surface cracking varies considerably, though a
value of 0.03% at an age of one year under unaccelerated conditions might be a
distinguishing value (Johnston 1974).
The value of the existing documented research is limited because of sparse and generally
negative results, and because waste glass was considered almost exclusively as coarse
3
aggregate. The present research expanded on these past efforts with further consideration of
material likely to be used in the practical application of waste glass. The range of glass types
studied was beyond those previously considered, particularly using frnely crushed (<I .5 rnrn)
and powdered (40 ym) glass. Actual municipal waste streams have been used throughout
the research - addressing concerns of contamination, washing and crushing, and use of the
aggregate by construction personnel. Admixtures used in this study included high-range
water reducer, and more important for practical use, air-entraining admixture and three
different sources of fly ash. The effectiveness of these fly ashes as a preventative measure for
ASR and the practical effects of the admixtures and the condition of the waste glass were
evaluated in the laboratory and in field trials.
The problems studied arise from the properties of waste glass as they differ from those of natural
aggregates. Waste glass aggregate particles smaller than about 3 mm have a sub-angular shape
and a smooth, flat surface texture. Particles larger than about 3 mrn exhibit a plate-like structure
remaining from their original form as glass containers, as well as considerable £riability, possibly
arising from macroscopic stresses and defects in the glass, either as manufactured or as crushed.
Smaller particles exhibit a more regular shape and reduced fiiability. Photographs of glass and
sand particles of several sizes are shown in Figures 1.1 - 1.6.
-
- photo f i l e
-
FIGURE 1.3. - ~oToMIcROGRAPH OF NATURAL SAND, D 0.6 MM
-
- photo f i l e
FIGURE 1.4. - PHOTOMICROGRAPH OF GLASS AGGREGATE, D - 0.6 MM
Waste glass is an amorphous or cryptocrystalline silica mineral, which may interact with the
hydration of cement paste, and which may be expected to take part in the alkali-silica reaction as
described by Hobbs (1 988).
When waste glass is used as aggregate, the principal difference in the structure of the resulting
concrete, and therefore its strength and durability, is expected to be the bond f o d between the
aggregate and cement paste. The interlocking shear strength between the aggregate and the
cement paste is expected to be less with glass than with natural aggregate. In addition, the
hbility of crushed glass particles may weaken the concrete structure. The chemical bond, if any,
between the aggregate and the cement paste might be greater for glass aggregate due to its
amorphous surface potentially allowing pomlanic behavior. The properties of interest in
evaluating the effect of glass aggregate on the structure of concrete are strength and bze-thaw
durability as industry standard indicators of performance.
Besides the possible Werences in physical structure caused by glass aggregate, other, and possibly
more sipficant changes are the differences in pore solution chemistry caused by glass aggregate.
Among the reactions of interest is the alkali-silica reaction (ASR), which may cause deleterious
expansions and strains in the concrete structure. The reactivity of amorphous glass has been
demonstrated by researchers to depend upon the surface characteristics of the particles, including
the speciiic surface, which is dependent upon the gradation of the particle distribution. Tang, et.
al. (1987) dernonstrated that the reactivity is particularly dependent upon the chemical
composition of the glass, becoming notable when the ratio ([SiQ]+[Naz0]):([CaO]+[A1203])
exceeds 1 and increasing sharply when it is greater than about 10 to 20; container glass may
typically have a ratio of about 6 to 10 and is thus expected to be reactive. ASR must be evaluated
and possibly mitigated, and other sigN6cant changes in pore solution chemistry may have to be
evaluated before glass will be viable for use as aggregate in portland cement concrete.
Other technical considerations also enter into an evaluation of the usability of glass aggregate.
Glass aggregate might affect the use and control of water during concrete mixing; thereby
affecting the working, forming, and finishing behavior of the concrete. Variations in glass waste
streams might be sigdkant, depending on the sensitivity of the resulting concrete to small changes
in composition or characteristics of the glass aggregate, and depending on the amount of variation
found to be in typical waste streams. Also, the aesthetics and public acceptance of the resulting
concrete will require some consideration, to overcome any perception of glass aggregate as an
inferior or unsafe material.
Finally, the costs of glass aggregate concrete will eventuaJly require consideration, though this is
not within the scope of this research. While an obvious benefit would be the savings of glass
disposal costs, the additional costs of grinding, grading, and washing the glass, and the costs of
additional water reducer, airentraining, or other admixtures will have to be included in such an
analysis, along with the additional costs or savings which might come kom the use of fly ash,
powdered waste glass, or other products used to m o w the mix.
It is hypothesized that waste glass aggregate, graded between RlOO and P8 and replacing up to
50% of the fine aggregate, may be used to produce concrete which will perform satisfactorily at
early to moderate ages and as well as similar natural aggregate concrete at later ages. The ratio
water:(cement + fly ash) by weight, w/(c +fi, may be used as an adequate predictor of the strength
and durability of concrete incorporating waste glass aggregate at wl(c +fi between 0.35 and 0.50,
the W/(C +fi usable in pavement and practically obtainable with the addition of high-range water
reducer. Prehnary results (Cramr and de la Cruz 1994) suggest that concrete incorporating
waste glass aggregate of an optimum form shows less strength and durability at early ages and
more at later ages than similar concrete using only natural aggregate. Further, when the waste
glass is graded as expressed above and processed as detailed in this research, and is used as 20%
or less of the total aggregate, the proportion of glass to natural aggregate has only a secondary
effect on the strength and freeze-thaw durability of the concrete, particularly at early to moderate
ages (less than 180 days).
It is also clear that waste glass aggregate is highly alkali-ska reactive, regardless of the form of
the glass, in agreement with previous researchers' conclusions (Johnston 1974). The ASR
deterioration may be effectively mitigated, however, by the appropriate use of mineral admixtures.
Fly ash of the type and composition detailed in this research may be used to mitigate ASR
deterioration at cement replacement levels of 10% to 20% when used with glass graded as above
- a somewhat lower cement replacement level than that found necessary by other researchers
including Johnston (1974).
It is also hypothesized that powdered waste glass ( 4 0 pm) may be used to supplement
cement in a concrete mixture containing waste glass aggregate. Because of its amorphous
silica composition, it is expected that it wdl mitigate ASR in much the same way that fly ash
might.
The objectives of this research are:
1. Identify gradations and characteristics of crushed waste glass, powdered waste glass, fly ash,
and chemical admixtures that produce concrete with adequate strength, fieezelthaw and
ASR durability, and usability in the laboratory and under field conditions for pavement
applications.
10 .
2. Docmnt the alkali-silica reactivity of waste glass aggregate, and determine mans of
mitigating this ASR - considering the addition of fly ash or powdered glass, limiting
cemnt alkali levels, and limiting water contents as possible mans.
3. Determine the effects of waste glass aggregate and powdered waste glass on the strength
and fieendthaw durability of concrete.
Evaluating various combinations of glass aggregate and other constituents will include
consideration of strength, freezeJthaw resistance, and resistance to ASR deterioration at ages
from one month to three years as indicators of quality. Both coarse and fine waste glass
gradations and several different glass preparation methods are included in the trials. Glass
proportions of 0% to 90% of the total aggregate and four fly ash compositions in proportions
of 0% to 35% of the total cementitious material are employed. Various water contents,
entrained air contents, and several water reducing and air-entraining admixtures are also
included in these trials.
The strength and durability of field trials of waste glass aggregate concrete will be evaluated
by comparison with typical specification and use requirements and by comparison with
corresponding laboratory specimens. This is undertaken to identify changes in the behavior
of the concrete under field moisture, temperature, exposure, and use conditions, and to
identify potential production problems (e.g., control of mix water, workability, air
entrainment, mixing, finishing, curing, etc.).
The measured strength behavior and the development of strength will allow differentiation of
several effects of glass aggregate:
The increased water requirement to utilize waste glass aggregate - observable in the
varying water content necessary to achieve constant workability with varying glass and fly
ash proportions. From preliminary results this appears to account for a large portion of
the observed differences in strength (Cramer and de la Cruz 1994).
The strength of the glass aggregate or lack thereof, i.e., its susceptibility to fracture -
particularly observable in an examination of the fracture of concrete containing the more
friable coarse glass particles.
Finally, the effects that are clearly present but cannot be attributed to either changing
water content or the strength of the glass aggregate itself may be regarded as intrinsic to
the behavior of glass aggregate in the concrete matrix. These would include differences
between the natural aggregate-cement bond and the glass aggregate-cement bond, the
possibility of a pozzolanic reaction between the cement paste and the glass aggregate,
which may contribute some strength, particularly at later ages, and changes in the cement
paste caused by the presence of glass aggregate, though this is not likely a contributing
cause of the observed differences.
The effects of fly ash on strength will be addressed, because mitigation of ASR generally
requires use of fly ash, and the variabihty of fly ash's effects and its interactions with waste
glass may be as significant as the effects of the waste glass itself. .
To allow the application of glass in a wide range of pavement concretes, some understanding
of interactions between waste glass and air-entraining admixtures, water-reducing admixtures,
fly ashes and finely powdered waste glass is necessary. These interactions will be studied in
terms of their effects on water demand, strength, freeze-thaw durability, and ASR in
laboratory experimentation.
12
Documentation of the current state of theoretical understanding of the nature of the ASR and
its operation in this particular application m a y shed some light on the significant pore solution
chemistry. Quantification of typical amounts of expansion at various ages and the effects of
glass gradation and processing procedures on ASR expansion m a y allow more consistent
application of ASR mitigation measures in waste glass aggregate concrete.
HYDRATION
Concrete is a composite of various mineral phases (aggregates, cement, fly ash, microsilica, etc.)
with sigmficant porosity and water either fdhg pores or bound into hydrated mineral phases. The
strength and durability of concrete comes fiom the development of a matrix of hydrated cemnt
which binds these mineral phases together. The properties of concrete depend both on the overall
arrangement and structure of the mineral matrix, and on the cementitious materials.
The strength developed by a concrete matrix &pends upon the porosity of the concrete matrix and
the strength of the paste-aggregate bond. The usual masure of concrete quality, w/c, the ratio
waterxement by weight, is itself a major determining factor of the porosity, because the water
which remains fiee fiom the cemnt hydration occupies volume within the matrix and creates
porosity. The paste-aggregate bond strength is in turn dependent upon the texture of the
aggregate surface and also upon the porosity and wlc ratio, because h e water tends to bleed to
the paste-aggregate interface and create voids which are then filled with weaker clusters of
Ca(OH)2 crystals (Roberts 1989).
Besides the wlc ratio, a major factor in determining the porosity and thereby the strength of the
concrete is the gradation of the aggregate and other mineral constituents of the concrete mixture.
The total combined gradation of the coarse and tine aggregate, cement and other mineral
admixtures ultimately determines the packing density of the total concrete mixture, though it may
be necessary to use plasticizers (primarily surfactant deflocculating agents) to allow the finest
particles of fly ash and silica fume to contribute to an efficient packing structure.
Durability, the ability to maintain structure and strength over time, is at least as important as
compressive strength in the performance of real concrete structures and pavements. Two possible
durability failure mechanisms that are most s i p k m t for pavement concrete with glass aggregate
are ASR, a problem particular to silica aggregates which will be discussed in depth in the next
section, and freedthaw damage. Freedthaw durability has been found to depend upon several
key factors: entrained air, permeability, and the quality of the cement-aggregate bond (Bjegovic,
et. al. 1987).
COMPOS~ON AND MICROSTRUCTURE
Cement is composed of 3CaO-Si02 (C3S), 2Ca0.Si02 (C2S), 3Ca0.AkO3 (C3A) and
4Ca0.&O3.k2o3 (C4AF). The cement compounds are soluble in water, and while in solution
CaO and SiO2 will hydrate to form calciumsilicate-hydrate gel (CSH) and calcium
hydroxide (CH). Both CSH and CH are less soluble than their constituents, and will therefore
precipitate from the resulting supersaturated solution, preferentially at nucleation sites (Neville
1981). The composition of solid CH is fixed while the composition of CSH may vary
with C:S ratios typically ranging between 1.4 and 2.0, but the C:S ratio may be substantially lower
in the presence of reactive silica or fly ash.
The effects of various materials on C:S may be illustrated with the solubility interaction dngrarn
for Si02 and CaO shown in Figure 2.1 (Brown 1989). As C3S dissolves, the composition of the
pore fluid develops along the labeled d~ssolution line. Upon crossing line AI, the solution becomes
supersaturated with CSH. When a critical degree of supersaturation is reached, represented by an
arbitrary point S on the diagram, CSH will precipitate with a composition Q, while the pore
solution from which it precipitates will be left with a composition P. The pore solution has thus
been enriched with CaO, as P lies to the right of the original dissolution line, and dissolution will
proceed along a line through P, parallel to the original dissolution. This process of developing a
supersaturated solution and precipitating CSH with C:S becoming progressively higher will
continue until the composition of the solution reaches point I. Until dynamic equiliium is
reached, the composition of the pore solution may extend metastably along the line IL, but the
dynamic equ ihhm will eventually settle at the point I, where CI.,SH and CH may precipitate
stoichioxmtridly h m the pore solution. The usual pattern is that I is approached h m the left,
the pore solution composition continues mtastably along IL, and the composition hally settles
again at point I, approaching h m the right, about 24 hours after mixing begins (Brown 1989).
0"
" 2 0 J Ca o Mol % C a O
FIGURE 2.1. S O L U B ~ IN'IERAc~oN DIAGRAM FOR S I ~ AND CAO. (BROWN 1989)
The hydration of C2S proceeds similarly, with a shghtly steeper dissolution line, initially
intersecting the line A1 to the left of B, but to the right of A
The effect of a pozzolan, contriiting reactive silica, may also be illustrated with the use of
Figure 2.1. The pore solution composition may settle into a dynamic equilibrium anywhere
between A and I, with I being the case where all (currently) available SiQ is incorporated into
CSH, leaving s o m excess Ca(OH)2, while A represents the case where all available Ca(OH)? is
incorporated into CSH, leaving som: excess SiQ. It is clear, thus, that the presence of a
pozzolan, and its availabhty or reactivity or tim= will affect the composition of both the pore w
solution and the CSH geL
The alkali-silica reaction (ASR) is a reaction between silica (SO2) and hydroxide ions (OH] which
forms an expansive alkali-silica hydrate gel, capable of imbibing moisture and thereby producing
sufficient expansive pressure to cause substktial cracking and deterioration of concrete. This
mechanism of expansion has been verified by Gillott and Beddoes (1981) by analysis of changes in
refractivity indices of opal undergoing reaction.
High concentrations of OH- in concrete pore solutions are caused by the presence of Na' and K'
ions, because of the high solubility coefficients of NaOH and KOH. One of the essential roles of
the allcalis in ASR is thus to raise the pH of the pore solution, because Si02 is relatively insoluble in
neutral and acidic environments, but quite soluble in solutions with high OH' concentrations
(Lane 1991).
ASR deterioration depends upon the presence of reactive (i.e., soluble) silica, a high OH-
concentration, usually facilitated by a substantial concentration of alkalis, and moisture for the gel
to imb1Ibe and expand (a requiremnt of at least 80% relative humidity has been established by
Stark, et. al. (1993) and Hobbs(1988), while Ludwig (1981) suggests 85%). The consistent
mitigation of ASR continues to be hampred, however, by lack of understanding of certain key
aspects of the reaction, and deficiencies in current test mthods.
A phenomnon which has been observed and recogwed by a number of researchers is what is
called the 'pessimum' behavior of many reactive silica aggregates. The pessimum content of an
aggregate is that amount of aggregate (e.g., expressed as kg of reactive aggregate per m3 of
concrete) which causes the largest ASR expansion. Researchers have observed that either
increasing or decreasing the aggregate content fiom the pessimum reduces ASR. The reason for
s o m aggregates showing pessirnum behavior, rather than simply causing increased expansion with
increased aggregate content, is not definitely known, though there are several good theories as to
why expansion may decrease beyond the pessirnum content of reactive aggregate given below.
The osmotic potential may be higher for a gel with a high alkali content (Diamond 1975); i.e.,
the potential difference involved in the hydration of water into such a gel may be higher. This
would suggest that increasing the silica content while keeping the akah content constant will
result in progressively kss osmotic gels, offsetting the increased quantity of gel produced.
It may be due to an optimum R20:Si02 ratio at the pessirnum content; if alkah is necessary for
the formation of a reactive gel, then as the pessimum proportion is exceeded, the alkali will
become too dilute for much expansion to take place.
In the accelerated test, the pessimum proportion may be due to production of large amounts of
gel which blocks pores and prevents the ingress of NaOH into the interior of the specimen
(Shayan 1992). B6rub6, et. al. (1995b) hkewise suggest that the accelerated test not be used
for evaluation of the pessirnum proportion of a given aggregate, but rather only be used for
establishing safe upper limits for use of an aggregate (below the pessirnum content).
Alkalis are properly those elements occupying the first column of the periodic table: Li, Na, K, etc.
The alkalis of concern are sodium and potassium, both because of their common o&urrence as
constituents in cement and aggregates and because of their demonstrated role in ASR. Other
alkalis have not been demonstrated to be problematic, in fact, lithium has been shown by a number
of researchers (Stark, et al. 1993; Diamond 1975, among others) to have a mitigating rather than a
contributing effect on ASR.
The alkalis which contribute, to ASR may corm fiom a number of sources, most commonly the
cement, the fly ash or other mineral admixture; less commonly fiom aggregates or the external
environment. The alkalis in fly ash or aggregates are ini* bound into glassy mineral phases,
which must dissolve for the alkalis to become available. For this reason, significant contributions
from aggregates are rare, due to the relatively low specific surface area of normal coarse or fine
aggregates and therefore low availability for dissolution. It is only in the fine gradations of cement,
fly ash or similarly graded materials that sufficient dissolution occurs for sigmficant alkalis to be
released.
The alkali content of a concrete mixture may be expressed by the alkali content of the constituents
(percent by weight of the cement and fly ash), on a bulk concrete basis (percent by weight of the
concrete or mass of allcalk per m3 of concrete), or indirectly by the OH- concentration (or pH) of
the resulting alkali hydroxide solution (OH' concentration (normality) = 0.339(Na20e of
cement)/(w/c) + 0.022 molesiL) (Stark, et al. 1993). In any case, alkalis in whatever chemical
combination they originate are usually quanti6ed by the equivalent normality of Na20 (equivalent
Na2O = Na20, = ma201 + 0.658[K20]).
Typical total alkali contents (Na20.4 are
low-alkali cement 0.40% - 0.60%
moderate-alkali cement 0.60% - 0.90%
high-alkali cement >0.90%
fly ash 0.50% - 5.00%.
A normal cement paste made with a cement containing = 1% Na20, and a w/c ratio = 0.50 has an
alkali concentration = 0.7 rnmoledL and pH = 13.7 (BkruM, et al. 1995b).
In cement, most alkahs are bound within the mineral phases, and the mineral phases must dissolve
for the alkalis to enter solution. Thus, the alkalis in cement will nearly all enter solution eventually,
as most all of the cement dissolves in a concrete of usual wlc. The alkalis present in fly ash, on the
other hand, may not enter solution, or may do so only very slowly as the £ly ash dissolves. Much
of the fly ash in a typical concrete never dissolves, and thus never contniutes its alkalis to the pore
solution.
The alkalis which do find their way into solution, meanwhile, are not necessarily available for
participation in ASR, because most will have already participated in hydration and pozzolanic
reactions (Duchesne and BCruE 1994a). Particularly for pozzolanic materials such as fly ash,
many researchers have produced results which suggest that more alkalis are incorporated into the
resulting pozzolanrc products than are released by fly ash dissolution. This may be an
electrochemical effect of the low C:S gel produced in the pozzolanic reaction (Scrivener 1989).
Scrivener has found that the surface charge of CSH is positive for C:S above about 1.3, and
negative for C:S below 1.3. Low C:S gel which is developed in the presence of a highly reactive
pozzolan as discussed above, would thus be much more capable of entrapping alkalis
electrochemically. Duchesne and BCruE's results indrcate that the amount of alkalis released by
fly ash is a function of the alkali content of the fly ash, while the amount of alkali which the
pozzolanic reaction removes fiom solution may depend on the pozzolanic activity of the fly ash,
but not on the akah content of the fly ash; this is also in agreement with Scrivener's model. In light
of these researchers' conclusions, Hobbs' (1986a) suggestion that 17% of the total Na20, of fly
ash be considered available may be too conservative for low-alkali ashes and not conservative for
high-alkali ashes.
BCruE, et d. (1995b) found that all mortar mixtures capable of reducing the alkali concentration
to under 2% Na20, (or 0.64 mmolesL) will satisfy the accelerated mortar bar test method.
Jones (1988) found that the viscosity of the ASR gel may depend on the ratio of alkalis to SiO2;
with gels having a low alkaksilica ratio being more fluid.
ROLE OF SILICA
The silica aggregates which may take part in ASR are generally those with an amorphous or a
highly disordered- or crypto- crystalline structure. Such a structure will dissolve readdy in high pH
environments and has greater surface reactivity and susceptibility to surface disruption and
breakage. Many natural reactive aggregates, e.g., opal, have a microporous structure that allows
the reaction to take place through much of the v o l ~ of the aggregate (Gillott and Beddoes
1981). The non-porous structure of glass aggregate may slow the 'reaction for some particles -
limiting the reaction to the surface of the particle; while also making the reaction much more
surface area dependent.
ROLE OF WATER
The availability of water throughout the concrete matrix is required for ASR to proceed:
to satisfy stoichiometric requiremnts to develop the ASR gel itself,
to provide a medium through which reactants may be transported to the reaction site,
and to develop expansive pressure through continued uptake of water by the expansive gel.
In addition, the ion collcentration of the pore solution is inversely proportional to the d c ratio, and
Lemer (1981) has suggested that rapid hydration of a low wlc concrete will allow little ASR
during the initial plastic phase and simultaneously increase the ion concentration in the remaining
pore water, possibly exposing the concrete to greater ASR stresses than if the strength had
developed more slowly. Also affecting the availability of water are the porosity and permeability
of the matrix. Besides allowing bulk movement of water through the matnx, the porosity
determines the mean distance of cemnt paste to be found between a reactive aggregate particle
and the capillary pore system. On the other hand, higher porosity does provide space for the ASR
products to expand into without exerting stress on the concrete matrix. These opposing influences
- of water content may produce a pessirnurn phenomenon associated with water content in addition
to that associated with aggregate fineness and proportion.
The effects of water reducers on ASR have been studied by Lenzner (1981), with observations
that ASR is accelerated by water reducers at a given wlc ratio, while the ultimate ASR expansion
is decreased. This observation that accelerated ASR is usually accompanied by reduced ultimate
expansion is in agreement with Jones (1988) and others.
GEL FORMATION
The development of alkali-silica gel may be d e s c n i as a reaction in which alkali ions and
hydroxyl ions enter reactive silica grains, leaving behind ca2', based on work by Chatterji, et al.
(1989):
Reactive silica + 2 Na' + Ca(OH)2 (aq) + aq + Sodium silica complex + ca2' + aq
K? may replace Na' in the above reaction; and it may be noted that the possibility of this reaction
and its rate will depend on the available concentrations of reactive silica, alkalis and Ca(OH)2 in
solution. This gel has been d e m i by Regourd, et al. (198 1) as having a structure and texture
to CSH developed from cemnt hydration, though with observed C:S ratios between 0.2 and 1 .O.
MECHANISM OF EXPANSION AND DJ~ERIoRATIoN
The actual ASR deterioration occurs due to the expansive pressure resulting from the absorption
of water in the ASR gel eventually overcoming the tensile strength of the concrete matrix, leading
to cracking and loss of stitkess and strength. Det-ntal effects due to ASR are dependent upon
both the formation of the gel and the uptake of water into the gel and to a lesser extent, the
degree to which the concrete is able or not able to accommodate gel expansion without being
strained, or have sufficient strength to restrain the ASR gel. Regourd, et al. (1981) have verilied
that concrete made from expanded reactive aggregate was able to resist expansion by
accommodating reaction products within the pores of the expanded aggregate.
22
There is considerable experhntal evidence, e.g., Jones (1988) and especially Gillott and Beddoes
(1981), to suggest that the swelling process is analogous with osmosis, being dnven by the lower
chemical potential of bound, hydrated water versus fire water.
Jones further divides the swelling behavior into two phases:
stage A: gel hydration and swelling
stage B: dissipation of gel £tom the generation site
He suggests that expansion can only result if stage B is considerably slower than stage A,
otherwise gel will be produced and dispersed with no development of mechanical pressure on the
concrete matrix. Ludwig (1981) has likewise verified the osmotic mhanism by comparing
observed concrete matrix forces with those predicted by osmotic pressure theory.
On the other hand, Chatterji and Christensen (1990) have developed a more thorough theory
which includes but goes beyond those of Jones and others, suggesting that the expansion of ASR
gel is due not simply to absorption of water, but rather a net m a t e d flow into the reactive grain
including Na', ca2+, OH-, and H20. In those cases where expansion is avoided, they suggest that
it is because in those cases silica migrates out of the reactive grain as quickly material moves in.
The rate of migration of silica out of the grain depends on the grain size (for a large grain, silica
has to move Mher to leave the grain) and on the concentration of Ca2+ in the pore solution
(continued migration of silica depends on the availability of Ca2+ outside of the grain to react with
the exiting silica, thereby precipitating CSH; otherwise silica concentration reaches equhbrium and
migration stops). Chatterji and Christensen illustrated this effect by developing a characteristic
constant K quantlflmg the amount of swelling induced in a standard alkali solution by various fine
aggregates. They found that K tends to zero as the fineness approaches that of cement, or as the
Ca(OH)2 concentration of the pore solution tends to zero.
Several methods have historically been available for the evaluation of ASR and means of
mitigating it. Chemical tests, such as ASTM C289, expose reactive aggregate to a standard
solution of alkali hydroxides, then use spectroscopy or other analytical chemical methods to
evaluate the progress of the reaction. This and similar tests have been criticized recently, most
notably by Stark, et al. (1993), as being too lenient and being limited to evaluating aggregate in
isolation. The effects of the cement, mineral admixtures, water content, and other variable
paramters of a concrete mix cannot be addressed by these tests.
CONCRETE AND MORTAR PRISM TEST ~ ~ T H o D s
The consensus among most researchers is that tests should be conducted with concrete or mortar
prisms. The prism test in longest use is ASTM C227, which exposes mortar prisms to a standard
moist environment and monitors the expansion developed due to MR. This test has also been
found to be somewhat lenient, particularly when low alkali cement is used to mitigate the reaction;
for example, this test generally gives good results with low aJkali cement, though they are not
always effective in practice (Stark, et al. 1993).
What most all researcher agree on, however, is that the ideal situation would be to test concrete
prisms, because the material can then be made identical to that prepared in practice, and no
extrapolation of results is necessary from the test mix and test materials to those of the field
concrete. The expansions m u r e d for concrete prisms have still been found to be affected by the
dimension of the prism (Curtil and Habita 1994; Rogers and Hooton 1991); therefore standardized
prisms should still be used to allow comparisons between different researchers' results. The
primary drawbacks to concrete prism testing are storage requirements for the relatively large
specirm=ns and the long period of time for the unaccelerated reaction to manifest itself- for these
reasons, concrete prisms tests are rarely used in practical research
A test which has been developed more recently by Davies and Oberholster (1987) and which has
now been adopted by ASTM as C1260, is an accelerated mark bar test using a concentrated
alkali hydroxide solution and an elevated temperature to achieve the acceleration. It is now among
the most common accelerated methods used for evaluating potential aggregates. This test appears
to be capable of determining the required quantity and characteristics of fly ash necessary to
mitigate ASR. Several researchers have further defined the paramters which may be expected to
affect the results of this test. Dubberke (1994) has found that the angularity of the aggregate used
in the test has a significant effect because an extremely angular aggregate may limit packing and
increase porosity at a given wlc ratio. Fournier and Berub6 (1991) have documented the effects of
WIC ratio and temperature of testing, and determined that cement composition does not have any
sigdcant mfluence, though they speculate that it might if moderate concentrations of NaOH were
used. (They found that at low concentrations of NaOH the NaOH pulled the OH- concentration
down regardless of the cement alkali content, while at high NaOH concentrations, the NaOH
pulled the OH- concentration up regardless of the cemnt alkali content.) It is somwhat
surprising to many that this accelerated test works to obtain consistent results with fly ash,
considering that the test specimens are completely immersed in a high-alkali NaOH solution, and
the most critical mechanisms involved when fly ash mitigates ASR are alkali dilution and
entrapmnt of alkali ions in CSH (B6rub6, et al. 1995b). BCrub6, et al. found, however, that even
in the accelerated method the alkali concentration of the mortar pore water correlates well with the
expansion results for all samples. This indicates that the method is appropriate for testing with fly
ash because the rrwhanisms by which mitigation occurs in the test method and in concrete in
practice are still the same. B6rub6, et al. do, however, add the caveat that the test may be
inaccurate at hgh alkali contents, and suggest keeping the total alkali content of the bars to no
more than 1.25% Na20, by weight of the cement.
E V A L U A ~ N OF TEST RESULTS
The allowable limit for ASR expansion to be acceptable is an important consideration with any of
these prism test methods. Some researchers, notably Hobbs (1988), base their recommndations
on the mechanical properties of the concrete, particularly the expansion necessary for cracks to
develop (approx. 0.03 - 0.05%). The standard Canadian evaluation methods using concrete
prisms is regarded as among the most reliable, with a expansion limit criterion of 0.04% (BCruM,
et al. 1995b). Others, notably Stark, et al. (1993), base their recommendations on correlations
between observed expansions in laboratory tests and observed performance of corresponding
concrete in field applications. Their recommndations are between 0.08% and 0.20% as critical
amounts of expansion after 14 days of ASTM C1260 testing.
Alongside the allowable limits of expansion, consideration must be given to the environment used
in the test, and methods must be used to provide experimntal control of possible environmental
variation, particularly with the longer term concrete prism tests. Rogers and Hooton (1991) have
studied various storage schemes for concrete prisms, finding that storage in a sealed box with the
prism held above water, but not 'immersed, and with a temperature of 38°C gave the most
expansion. Prisms stored at 23°C in the wet room showed substantially less expansion with some
evidence of leaching of alkalis fiom the concrete. They noted that it is important to use a reference
aggregate as a control and develop a criterion for acceptable expansion based on its performance.
Other properties of concrete have been explored as indicators of ASR, particularly compressive,
tensile and flexure strength (Curtil and Habita 1994). but have limited use because of the normal
variation in these properties due to variation in aggregate, cement, and mineral admixtures.
Several methods have been successfully used to mitigate ASR deterioration as reviewed by Gillott
and Wang (1993):
Pozzolans may reduce the C:S ratio of the pore solution and the resulting CSH, thereby
trapping alkalis on their surface and preventing movement of alkalis into reactive silica grains
(Duchesne and BCrubd 1994~). However, because this electrostatic trapping is weaker than a
true chemical bond, this may only slow the movement of alkalis and slow the reaction without
completely stopping it.
There appears to be a critical alkali content below which expansion does not occur (BCrubd, et
al. 1995b); thus, limiting total alkali content in the mix should mitigate MR. Duchesne and
BCrubd (1994a) suggest a limit of 300 kg/m3. This method may not be reliable because of the
difficulty of ensuring that additional alkalis do not enter the concrete at some point during its
lifetime.
Retarders may delay the formation of a rigid microstructure sufficiently to allow ASR to
proceed to completion without disrupting the concrete matrix. Retarders have also been shown
to hamper nucleation and growth of Ca(OH)2 and decrease the rate of hydration of C3S and
C2S, thereby allowing pozzolans more time to enter the hydration reactions and decrease the
C:S ratios of the pore solution and the resulting CSH before high C:S ratios are reached.
Mineral admixtures may reduce permability and thereby prevent water from reaching and
being imbibed by expansive gel.
Air-entraining admixtures may introduce voids which will accommodate the expansive ASR gel
- note however that this solution may compromise the ability of the concrete to accommodate
kze/thaw cycles. Because of the mitigating ability of air voids, comparisons of ASR
expansion between airentrained and non-airentrained concretes must be made very cautiously.
The surfactant properties of air-entraining admixtures and plasticizers may affect the potential
gradient between fiee and hydrated water and their influence on surface.tension forces may
reduce the viscosity of ASR gels.
Introduction of LiOH or certain other alkali salts has been found to mitigate ASR, probably by
poisoning the alkali gel which is necessary for expansion to take place by occupying the
molecular positions which Na' and K? would otherwise occupy, but not producing the same
expansive properties within the gel (Stark, et. al. 1993).
Powdered glass might mitigate ASR by acting as a pozzolan according to the criteria set out by
Giott and Wang (1993) and Chatterji and Christensen (1990). There are, however, several
notable difference between glass and fly ash as potential pozzolans - s o n positive, others
negative:
The fineness of glass will depend upon the grinding method used; the effectiveness of a
pozzolan both for strength enhancement and for ASR mitigation is known to depend upon
fineness.
Glass is entirely amorphous, in contrast to fly ash which is often an amorphous layer covering a
crystalline core. This may or may not be an advantage for glass - Stark, et. al. (1993) have
developed a theory that the inner portion of a reactive grain may develop expansive ASR gel
while the surface does not, because of the different diffusivities of R+, ca2+ and ASR gel. If this
is correct, the structure of fly ash, with a layer of amorphous silica surrounding a crystalline
core, may be an ideal configuration for acting as a pozzolan in mitigating ASR without
contributing to ASR itself or contributing the majority of its alkalis to the pore solution.
The alkali content of glass may be very sigmficant - note particularly that in light of the theory
by Stark, et. al. mentioned above, the morphology of glass (entirely amorphous) may .be
detrimental and may allow nearly all of its alkalis to be released into solution, rather than the
10% - 30% observed by Hobbs (1986a) and corroborated by others.
FLY ASH
ASTM standard C618 classifies fly ashes as Class F or Class C with the following general
properties:
CIasJ? clas& Bituminous Coal Sub-Bituminous Coal
Low CaO Content High CaO Content
SiO2 + A1203 + FeQ 2 70% 50% I Si02 + A1203 + FeQ < 70%
History of Good Mitigation of ASR History of Poor Mitigation of ASR
Only Pozzolanic Pozzolanic and Cementitious
Both Class F and Class C fly ashes typically have a glassy morphology surrounding and
encasing crystalline inclusions (Fraay, et al. 1989).
The ASTM requirements for fly ash will be discussed with regard to the specific fly ashes used in
this experimental program in Chapter 3.
The effect of fly ash on the structure of concrete is, first, to act as a line inert material which
densifies the packing structure of the cement particles and provides nucleation sites for
development of a finer structure of CSH gel; and second, after some t k , the silica in the fly ash
reacts with the Ca(OH)2 developed by cement hydration and produces secondary CSH by the
pozzolanic reaction. This requires that the glass in the fly ash goes into solution first, however,
which only happens substantdly beyond a pH of about 13.2 to 13.3 (Fraay, et al. 1989). The
usual effect for a concrete which has had a portion of its cemnt replaced by fly ash is a sowwhat
lower strength at early ages, followed by a higher ultimate strength at later ages. The age at which
a fly ash concrete will equal and begin to exceed the. strength of a similar cement-only concrete
usual& varies from 28 to 90 days, though some may gain strength only much later. Monz6, et. al.
(1994) have found that the effects of fly ash on water demand and workability depend primarily on
the fjneness, shape and particle size distriiution of the ash, while the crystWamorphous ratio
and particle size distribution influence the strength activity. The strength activity of fly ash can be
broken down into two distinct effect: nucleation and pozzolanic activity.
It has been found by researchers generally, for example by Gopalan (1993), that the early
contribution of fly ash to strength development is primarily due to nucleation, while the later
contribution is primarily due to pozzolanicity. Babu and Rao (1994) have found that in many
cases the contribution of fly ash to strength during the first 7 days of hydration is entirely through
promotion of nucleation. Fly ash is able to enhance the strength of concrete simply by providing
nucleation sites during the early period because the abundance of nucleation sites refines the
structure of the CSH matrix and accelerates its development. The onset of pozzolanic activity by
fly ash is itself dependent upon the fly ash:cement ratio in the mix - as the relative proportion of
fly ash is increased, the onset occurs at later ages (Gopalan 1993). Fraay, et al. (1989) refers to
this period before the onset of pozzolanic activity as the 'incubation' period of the fly ash, but
agrees that the fly ash does contribute to strength by acting as precipitation nuclei during this
period. A high alkali content in either the cement or the tly ash, or both, will accelerate the onset
of pomlanic activity, because as the alkalis are released into solution, the pH of the solution will
be increased, leading to a more rapid dissolution of the glass phases in the fly ash wlc ratio
may also contribute to this effect, because a lower wlc ratio will result in a smaller volume of pore
water and higher concentrations of aJl of the chemical species (Fraay, et al. 1989). Fraay, et al.
also note that the precipitation of CSH around a fly ash particle, either due to nucleation before the
onset of pozzolanicity, or due to the pozzolanic reaction, will slow the dissolution of the fly ash
glass network. As the pozzolanic reaction continues into its later stages, the pH will tend to
increase because of the continuing decrease in h e water, and the S i a from the fly ash particle
30
will travel ever further distances before hally combining with CaO and precipitating as hydrated
CSH, leading to a more and more fmely re6ned pore structure in the cqncrete.
FLY ASH IN MTIIGATION OF W - S I L I C A REACTION
The effect of fly ash primarily of interest in this research is mitigation of ASR deterioration. There
are two prevalent reasdm for this effect:
The pozzolanic reaction lowers the C:S ratio of the pore solution and the CSH gel leading to
electrostatic trapping of alkali ions, and
of OH- ions and c ~ Z ' ions are consumed in the pozzolanic reaction.
A third possible reason - fly ash causing a reduction in pemability and thereby limiting water
transport - is difticult to defend because of the clear. &penden= of ASR-mitigating ability on
properties of fly ash which do not affect the developmnt of strength or reduction in permeability.
The properties of ily ash which primarily determine its effectiveness in mitigation of ASR are its
alkali content, and to a lesser extent its Si02 and A1203 contents (Duchesne and Berubi 1994b).
There are other effects of fly ash which also must be included in a consideration of fly ash as a
mineral admixture. The amount of airentraining admixture required to achieve a particular air
content is generally increased by the use of fly ash. The component of fly ash which actually
causes this is tke (i.e., chemically unbound) carbon, which is difficult to measure directly, but is
indicated indirectly by the loss on ignition. Fly ash may increase airentraining admixture
requirements by a factor of anywhere fiom 1 to 10 or more for very high k e carbon contents.
Fly ash also generally affects the amount of water required by the mix. Fly ash often decreases the
water requirement by 10 to 20%, but lower quality Class F ashes have actually been observed to
increase the requirement by up to 30%. These effects require carell consideration, especially
when using some of the poorly controlled Class F ashes, as they may dramatically affect the
procedures required in handling concrete in practice.
The availability of fly ash, especialEy high quality ash, is another consideration. Increasing demand
for high quality fly ash, coupled with changes in power plant operation in response to
environmental regulation and market forces, has increased the cost of high quality fly ash and
increased the quantity of low quality ash used in concrete applications. In many areas, the coal
power industry is moving to a scheme of marketing hrgh quality, controlled fly ash at sigmkant
markup fiom the (negative) cost of the raw material. In these cases, fly ash is more properly a
valuable by-product and not a waste product at all. The fly ash which remains available at cost or
for a nominal charge, on the other hand, is becoming of lower quality and exhiiiting more
variability, both fiom a single sources and between sources and regions (Mehta 1989).
POWDJZRED WASIE GIASS
Powdered waste glass, i.e., mixed color container glass ground to cemnt fineness or her , might
fill the niche of a lowcost waste material able to act as a Class F pozzolan with low variability.
The gradation of the glass used in this research is comparable to that of a fine fly ash, though
substantially coarser than silica furne, to which the glass might otherwise be chemically
comparable. The gradation of the powdered glass, those of the cements and fly ashes used, and
the typical gradation of a silica fume (presented only for comparison, not used in this research) are
given in Appendix 3.1.
The chemical composition of waste glass is also detailed in Appendix 3.1, along with those of the
cemnts and fly ashes used, and of a typical silica furne for comparison. The tripartite plots of the
systems Ca0-AlzQ-Si02 and Ca0-Na20e-Si@ in Figure 2.2 also ilIustrate the similarities and
differences between the various materials.
CaO F3 F ~ v A s u F 3
PC P o w o r r r o GUSS
F3 SF SILICA FUWL 0
, . . ' . . , . . . , *
FIGURE 2.2. TRIPARTITE COMPOS~IION PLOTS OF THE SYS'IEMS CAO-&O~-SIG AND CAO-NA~O,-SIG.
Beside their composition, however, the morphology and structure of the respective materials is
important to an understanding of their behavior in concrete:
Cement Ground Crystalline
Fly Ash Precipitated Amorphous surrounding a Crystalline Core
Waste Glass Ground Amorphous
Silica Funr= Precipitated h r p h o u s
It is expected that the action of these respective materials in concrete will depend on more than
simply their compositions. Powdered waste glass is similar in composition and morphology to
silica fume; but lacking the spherical precipitated shape and the extremely fine gradation, it would
not be expected to develop the characteristic behaviors of silica fume which are dependent on
these properties: enhanced densifkation of the transition zone, water reduction in concert with
hlgkrange water reducers, and microfiller effixts below the size range of cement and £ly ash
particles and therefore within the cement and fly ash packing matrix Goldman and Bentur (1993)
have performed some research to separate these different effects of silica fume, hdmg that an inert
filler (inactive carbon black) was able to reproduce the microfiller effect especially characteristic of
silica fume only when present in particles smaller than 0.073 p - smaller than the effective
gradation of either fly ash or the powdered glass. Likewise for the water reducing effect - it is a
general consensus (see Kheder and Abou-Zeid (1994) for a detailed discussion) that silica fume
exhibits its water reducing abhty afker it has been deflocculated by high-range water reducer
because it is at that point that the true spherical shape of its small particles is able to have an effect
because it is only then that the particles are acting individually in the rheology of the paste. This
understanding would suggest that powdered glass, with a ground rather than precipitated
structure, would not exhibit this same behavior. Silica fUme is also commonly observed to be
more cohesive than non-silica fume concrete, and produces less bleeding (Scrivener 1989). This
behavior might be duplicated by powdered glass because it adsorbs water in much the sam way,
ie. by removing water fiom the larger scale interfaces where it can contribute to bleeding and
prevent cohesion; without the extremly fine particles found in silica fume, this effect might be less
dramatic, however.
The effects of powdered glass on ASR are expected to derive fiom its pozzolanic and
compositional characteristics: its content of active SiG and resulting pozzolanic activity, its
effective alkali content, and its specific surface and dissolution behavior.
CHAPTER 3 - METHODS AND MATERIALS
The experimental program was conducted in several phases by various researchers: (a) a study of
the interaction of both coarse and fine waste glass aggregate and fly ash (the Glass-Fly Ash
Series), (b) a field trial in which the most promising mixes from the Glass-Fly Ash Series were
used in a sidewalk (the Field Trial), (c) a controlled laboratory test of the possible use of finely
ground glass as a cemnt supplemnt (the Powdered Glass Series), (d) and paralleling several of
the mixes in each of the previous series and fUrther examining the potential ASR interaction of
glass and fly ash, (e) a series of accelerated ASR expansion mortar bar tests (the Accelerated ASR
Series).
The Glass-Fly Ash Series began with a broad study to identlfy the effects of various proportions of
glass and fly ash on compressive strength and ASR (Phase-I). This first phase was conducted by
Guadette and Vimawala at the University of Wisconsin (Gaudette 1993; Vimawala 1992). As the
optimum proportions were refined in the subsequent phases, fi-eeze-thaw resistance, tensile
' strength, air entrainment, and water reducing admixtures were added to the experimental program
(Phase-II). The second phase was planned and begun by Cramer, Vimawala and Gaudette, with
the author joining the experimental effort during the implemntation of Phase-11. The experimntal
work subsequent to Phase-II was conducted by the author, some in cooperation with others
including Cramer, Bakke, Carpenter and Jackson.
Prehmary to Phase-I, work was performed to obtain waste glass aggregate and to wash and
grade the aggregate, to obtain the moderate-alkali cemnt used in Phase-I, and to research
potential use of Class C and Class F fly ashes to mitigate the expected ASR deterioration due to
the glass aggegate.
In Phase-I, the test matrix combined glass aggregate at 0%, 12%, 24%, 36%, 48% and 90%
replacemnt of natural coarse and line aggregate by weight, and fly ash at 0%, 20%, 25%, 30%
and 35% replacement of cemnt by weight, for a total of 30 mixes. Each mix was represented by
four replicate batches. Additional expekntal series were conducted during Phase-I to
investigate the effects of Class C vs. Class F fly ash and the effects of washed vs. unwashed glass
aggregate. No chemical adrnktures were used during these experimental series. It was intended
that this study would identlfy promising mixes for more intensive investigation and is d e m i in
the proposal by de la Cruz and Cramer (199 1).
As Phase-I was nearing completion, Phase-II laboratory trials were conducted with those
proportions of glass and fly ash which showed the most promise - specifically testing glass
aggregate replacementifly ash replacement ratios of 0%/0%, O%/25%, 12%/20%, 20%/20%,
24%/25%, 24%/30% and 36%/25%. The expehntal program was expanded at this point to
include kze-thaw resistance and longer-term strength and ASR testing and the effects of air-
entraining and water reducing admixtures. As the optimal mix proportions were fi.uther narrowed
at this stage, other sources and processing regimes were included for the glass aggregate, hlgh-
range water reducer and liner and more limited glass gradations were introduced in some of the
mixes (O%/O%, O%l25%, 20%/20% and 24%/25%), and several alternative sources of fly ash
were included (de la Cruz and Cramer 1991). Experimental control was provided by mixes with
O%/O%, no water reducer; 0%/0%, high-range water reducer; and 0%/25%, high-range water
reducer. The initial mixes for Phase-I1 were selected by Gaudette (1993) according to criteria of a
minimum 28-day strength of 2500 psi (17.2 MPa) and a maximum ASR expansion of 0.008%
after 180 days. After examining the results, fiom Phase-I, Gaudette found it necessary to relax
these criteria somewhat, and the mixes finally sekted (noted above) had 28-day strengths
between 14.5 MPa and 21.2 MPa, and 180-day expansion values between 0.008% and 0.01 1%.
It was from the Phase-I1 laboratory mixes that candidates were selected for the Field Trial. Based
on the results of all of the previous laboratory studies, the Field Trial was begun to test the
usability and performance of the concrete under typical site conditions. A sidewalk was
constructed with various trial sections including glassfly ash replacement fractions of 0%/0%,
0%/20%, 10%/15%, 20%/20% and 20%/25%, and two types of fly ash AJ of these sections
included air entrainmnt, and glass aggregate within a limited, fine gradation range; and all except
the 0%/0% control section included high-range water reducer.
Further work was then conducted in the laboratory to study the effects of powdered glass with a
mean particle size of approximately 45 ~ u n ; prepared fiom the glass aggregate stock by grinding in
a ball grinder. This material was treated as a cement supplement, supplementing the cement by
0%, 1%, 2.5%, 5%, 10% and 20% by weight, alI in mixes prepared with a wl(c +fi ratio of 0.43,
20% glass aggregate and no fly ash
A summary of all of the concrete mixes, both laboratory and field tnal, is provided in
Appendix 3.2.
The Accelerated ASR Series used mortar prisms stored at elevated temperatures in concentrated
NaOH solution to develop ASR deterioration within seven to fourteen days. Prelirmnary work
investigated and documented the ASR reactivity of glass aggregate, and provided baselines for
several evaluation of the accelerated ASR results. Subsequent series were used to determine the
pessimurn content of glass aggregate, to investigate the effectiveness of powdered glass and fly ash
in mitigating ASR at the pessimum content, and to parallel the Field Trial and Powdered Glass
Series concrete mixes, as well as several selected concrete mixes fiom the Glass-Fly Ash Series. A
summary of all of the accelerated ASR mixes is provided in Appendix 3.3.
AGGRFGATES
The natural aggregates stocked in the laboratory were used in the laboratory portion of the
research The coarse aggregate was a mixture of washed river gravel and crushed gravel; while
the fine aggregate was entirely washed river sand.' The aggregates used during the fmt portion of
the research differed somewhat fiom those used in the f ~ l d trials and during the later research, and
is denoted as aggregate A and aggregate B in the appendices. The moisture content of the natural
aggregate was tested for later use in calculating the resulting d ( c +j) ratio; with the exception of
the Powdered Glass Series, for which the aggregate was oven dried and used in a dry condition to
ensure a constant d ( c +j) over the entire series.
Glass aggregate was crushed container glass, obtained fiom a commercial municipal recycler.' For
those mixes using unwashed glass, the material was used as received. For the majority of the
mixes, however, the glass was washed and the fixtion smaller than 75 pm was discarded as part
of the washing process. For some of the mixes a reduced gradation was desired, and the material
smaller than 300 pm was removed by washing and discarded; while for some others, glass
aggregate was ground in the laboratory to increase the fines content (75 pm to 2 mm) before
washing. The washing process for the glass aggregate not only removed som dust, but also
dissolved and removed some organic contaminants, particularly sugars, and removed some light
components from the glass, particularly paper remaining from the original waste stream After the
' The natural aggregates were obtained locally through a donation by Lycon. Inc.
* The waste glass aggregate was obtained from M. J. Schmidt Corp. of Milwaukee according to the following schedule:
9/91 First Shipment of Coarse Glass and First Shipment of Fine Glass 2/92 Second Shipment of Coarse Glass and Second Shipment of Fine Glass
- . 7/92 Third Shipment of Coarse Glass 5/93 Fist Shipment of P8 Fine Glass 8/93 Second Shipment of P8 Fine Glass
glass .had been washed, its moisture content was controlled either by drying to constant weight . (WO moisture content), or by drying to between 0 and 2% moisture content, then testing a sample
by drying (ASTM C566) to determine the remaining moisture content.
Standard tests for gradation (ASTM C136), and specific gravity and absorption (ASTM C127,
C128) were performed with the results detailed in Table 3.1.
TABLE 3.1. AGGREGATE SPECIFIC GRAVITIES AND A B S O ~ O N S . Aggregate Specific Gravity Absorption (%)
Natural Gravel
Natural Sand
Waste Glass
Several distinct shipments of coarse and fine glass were used, and to match the gradation of the
glass aggregate as closely as possible to the natural aggregate which it replaced, different
combinations of glass gradations were necessary for the different aggregate replacement
percentages. The use of the various combinations of glass aggregates in the concrete mixes is
summarized in Appendix 3.2.
The glass aggregates used in the research are summarized in Table 3.2. The notation in Table 3.2,
along with other notation used to describe concrete mixes throughout this thesis, is proiided in the
Notation section before Chapter 1.
The gradations of the aggregates used are presented in Figures 3.1, 3.2 and 3.3. It may be
observed that the natural gravel and sand used as control aggregates are fairly constant throughout
the research; though Gravel B, used in the Field Trial and the later laboratory work, does have
somewhat more fine material than Gravel A, and Sand B, also used in the Field Trial and the later
laboratory work, is slightly coarser overall than Sand A.
TABLE 3.2. GLASS AGGREGATE SUMMARY DESCRIPTIONS. Designation Description
Washed, First Shipment of Coarse Glass
Unwashed form of Glass CA
Washed, Second Shipment of Coarse Glass
Washed, Blend of Glasses CC and CE
Washed, Third Shipment of Coarse Glass
Washed, First Shipment of Fine Glass
Unwashed form of Glass FA
Washed, Second Shipment of Fine Glass
Washed, Gradation #1 Ground in Laboratory from Glass FC - extremely flaky particle shape
Washed, Gradation #1 Ground in Laboratory from Glass FC - extremely flaky particle shape
Unwashed form of Glass FG
FG Washed, First Shipment of P8 Fine Glass
FH Washed, form of Glass FG with P50 fraction discarded
FI Washed, Second Shipment of P8 Fine Glass, used in Field Trial and Powdered Glass Series, similar to FG with less RlOO fraction retained during washing
Washed, limited, standardized gradation of Fine Glass for use in Accelerated ASR Series
Examining the coarse glass gradations in Figure 3.1, glasses CC, CD and CE are very similar,
while glasses CA and CB are similar to each other, but with significantly more fine material than
the other three and wider gradations. All of the coarse glass gradations, meanwhile, are h e r than
the natural gravel, with overall wider gradations; and the finest fiactions in the glass aggregate are
much smaller than the finest fiactions in the natural gravel.
0%
0.01 0.1 1 10 100 Particle Size (mm)
- Glass CA
.....................
. . . . . . . . ................. * .
. . . . . . . . . . . . . . . .
FIGURE 3.1. GRADATIONS OF NATURAL, GRAVELS A AND B, AND COARSE GLASSES CA CB, CC, CDANDCE.
- + - Accel. ASR Sand . . . . . . . .
. . . . . . . .
0%
0.01 0.1 1 10 Particle Size (mm)
FIGURE 3.2. GRADATIONS OF NA'IURAL SANDS A AND B, ACGLERA'IED M R GRADATION, AND FINE GLASSES Fk FB, FC, FD AND FE.
The fine glass gradations in Figures 3.2 and 3.3 show even greater variation. The natural sands are
finer and exhibit a wider gradation than any of the fine glass gradations. Glasses FA, Fl3 and FC
are very similar to each other, with fairly wide gradations; while glass FE, ground in the laboratory
from g h s FC, is much narrower, with a high content (45%) of a single size fraction. Glass FD,
also ground in the laboratory from glass FC, has a somewhat wider gradation, with substantially
more fine material than glass FE.
Glasses FF and FG (Figure 3.3) show the widest gradations among the fine glasses; nearly
equaling the natural sand with finer gradations overall, though their greatest fraction is slightly
larger than that of the sand. Gradations FH and R are narrower and somewhat coarser than
glasses FF and FG.
0%
0.01 0.1 1 10 Particle Size (mm)
FIGURE 3.3. GRADA~ON OF NATURAL SANDS A AND B, AND FINE GLASSES FF, FG, FH, FI AND
FJ.
. . . . . . . . ......:.._. : _.:.. L ...:. L 2 . . . . . , . . . . . . . . . . . . .................................. . . . . . . . . , , . . . . . . . . , , . . , . . , . . . . . . ................................................. . . . . . , . .
. . . . . , . . - 9 - Glass FG
. . . , . . . . ................................ . . , . . . , . . . . . . . . . ... , . . . . . . --*--Glass FI-I
. . . . . . . . . , . . . . . . .............................. , , . . . , . . - + - Glass FI
. . . . . . . . ..................... .,. ........ . . . . , , . . , , , .
- -( - Glass FJ . . . . ........ . . . . .............................. . , . , , . . . . . . . . . . : -... :..'.:.:.*.: . . . , . . , . . . . . . . . . . . ................................ ............ .... ..... .- -. -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . ' . . . . . . . . . . . . . . . . . . . . . . . . . . ........ , .................. . . . . . . . . . . . . . . . . .......................... . . . . . . . . . . , , . , . . ... <.-... . , . . , , . . . . . . . . . . .......................... . . . . . . . . . . . . . , , . . . . . . . . . ,
. . . . . . . . . . . ....................... . , . . .
. . . . . . . . , . , . . , . . ........................ . . . . . . . .
.................. ' ' . . . . :.:.'.' . . . . . . . . . , - : i
.............. ........ . . . . . . . . .... . . . . . . . .
1
. . . . . . . . ...... . :. ...... 1 . . L 2. : . . . . . . . .
:.. . .:..:.:.:.:.I:".-:"? . . . . . . a . . . . . . . . . . . . , . . . , . . . . . . . . , . . . .,. . . . . . . . .
. . . . . . . ........ ...... ..:.. . -. ., C : _'_ : . . . . . . . . 1.. .:. :..: .:.:.:
! 2': : : : : : : t ' . . " " ... ... .. . . I . .;;- : :. : : .:. : . . . . . . . . . ,
-Sand A - ~ S a n d B - Glass FF
CEMENTS, FLY ASHES AND POWDERED GLASS
The powdered glass was obtained by grinding Glass FG in a ball grinder to an average particle size
of approximately 45 ~ u n ; its characteristics are given in Appendix 3.1. The powdered glass was
stored and handled in a dry state and was handled in the mixing procedures in a manner similar to
the cement.
Two type I portland cements were used during the research - one low-alkali (0.49 Na20e), and
one moderate-alkali (0.67 ~ a 2 0 , ) ~ . Fly ashes were obtained fiom one source of Class C ash, and
three sources of Class F ash4, and were characterized according to ASTM C618 (1993). The fly
ash used in the majority of this research has fallen roughly under the Class F classification. The
principal requirements of the ASTM fly ash classifications (C618) and the relevant characteristics
of the experimental fly ashes are compared in Table 3.3.
Several of the fly ashes used deviate from ASTM standards in some way; Fly Ash C appears to be
the only one which completely satisfies the ASTM requirements for its classification. Fly Ash F1
falls within the Class C limits on pozzolanic content ( Si02 + A1203 + Fe03 ), though it is
marketed as a Class F ash, and it also exceeds allowable limits on SO3 content and Na20,. Fly Ash
F2 is the closest to allowable limits - it is only over by 0.5% on the SO3 content. Fly Ash F3 has
substantnlly different characteristics fiom the other two Class F ashes, including its gradation. The
pozzolanic content actually falls within the Class C range, and the extremely high LO1 interferes
The low-alkali cement was donated by Holnam Cement Corp. The moderate-alkali cement was donated by LaFarge Corp. 4 The fly ashes were obtained according to the following schedule:
12/90 Fly Ash C WP&L Columbia Station 3/91 Fly Ash F1 WP&L Rock River-Blackhawk Station 8/93 Fly Ash F2 WP&L Rock River-Blackhawk Station
note that the Rock River-Blackhawk Station changed its emission control equipment between 319 1 and 8/93
7/94 Fly Ash F3 WEPCO Edgewater Station
with effective use of water reducing and airentraining admixtures and increases the fraction of
light particles present.
TABLE 3.3. ASTM C6 1 8 CLASSIFICATION P-S. Pozzolanic so3 Loss on Ignition Na20, Content (LOU ) 1 5 % 5 6% 1 1.5%
Fly Ash F1 68.0% 9.4% 0.2% = 1.7%
Fly Ash F2 76.4% 5.5% 3.8% = 1.1%
Fly ~ s h F3 61.2% 0.7% 15.2% = 0.8%
Powdered Glass .= 73% none none = 5% - 16%
ASTM Class C 50% - 70% 1 5 % < 6% 5 1.5%
Fly Ash C 64.5% 2.4% 0.2% = 0.5%
Complete details of the compositions and characteristics of the cements and fly ashes are tabulated
in Appendix 3.1.
Air-entr-nt was provided by a neutralized vinsol resin solution in compliance with ASTM
C260, with the dosage adjusted as necessary to achieve 5% to 7% entrained air. Water reducers
included a high-range water reducer (a modified naphthalene sulfonate solution, in compliance
with ASTM C494 Type F) and a mid range water reducer (a proprietary solution of dispersing and
finishing agents and hydration catalysts, in compliance with ASTM C494 Type A) - both
proportioned to a standard dosage within the manufacturer's recommendation^.^
. 5 The high-range water reducer was W. R. Grace & Co. WRDA-19 at a dosage of 3.74 urn3; the mid-range water reducer was W. R. Grace & Co. Daracem-50 used at a dosage of 1.98 urn3; the air-entraining admixture was W. R. Grace & Co. Daravair - The dosage of Daravair was adjusted is discussed in the text.
*
In keeping with the intended use in concrete pavements, the Wisconsin Department af
Transportation Standard Specification for Type A concrete highway pavement (State of WI
Specifications 1989) was used as the basis for the rnix design. To reduce the number of variables
requiring consideration, the DOT specification for concrete incorporating fly ash Standard Type
A-FA, was not used because the required total of cement plus fly ash for Type A-FA is greater
than the cement requirement of Type A.
It was necessary to deviate from the DOT specifications with regard to rnix water, because the
amount of mix water specified did not provide sufficient workability with waste glass aggregate;
thus to ensure workability, it was decided to spec@ a target slump for the research mixes, with the
expectation that the resulting water requirement would be greater than that in the DOT
specification. In Phase-I, the target slump was 75 mm; while starting with Phase-II, to more
closely approach the water requirement of the DOT specification, a target of 50 mrn was used. In
some of the mixes, in a further effort to approach the water requirement of the DOT specification,
a high-range water reducer was added while the target slump was retained at 50 mm.
The mix design specifications are summarized in Table 3.4 for the Wisconsin DOT Standard
Specification, Phase-I (batches 1 - 139) and Phase-II (batches 140- 178) of the Glass-Fly Ash Series,
the Field Trial and the Powdered Glass Series.
TABLE 3.4. SUMMARY OF MIX DESIGN SPECIFICATIONS.
WI DOT Glass-Fly Ash Series Field Trial Powdered TYFA Phase-I Phase-I1 Glass Series
Total Cement and Hy Ash (kg/m3)
336 336 336 336 336
Total Aggregate (kg/m3)
1873 1873 1873 1873 1873
Fine Aggregate, % of total aggregate
35-45 40 40 40 40
Glass Aggregate, % of total aggregate
None 0, 12,24, 0, 12,20, 0, 10.20 0,20 36,48,90 24,36
Fine Glass Aggregate, 136% Replacement Mixes
N/A 35% of 35% of 100% of 100% of total glass total glass total glass total glass aggregate aggregate aggregate aggregate
Fine Glass Aggregate, 24.8% Replacement Mixes
N/A 20% of NIA N/A N/A total glass aggregate
Class F Fly Ash, % of total cement and fly ash
None 0,20,25, 0, 20, 25, 0, 15, 20, None 30,35 30 25
Powdered Glass, % of cement
Entrained Air
None None None None 0, 1, 2.5, 5, ' 10,20
6%+1% None 6%+1% 6%&2% 6%&2%
High-Range Water Reducer (L./m3)
Mix Water (kg/m3)
None None 3.74 3.74 3.74
138 to 17 1 For 75 mrn for 50 mm For 50 mm 144 slump slump slump
CONCRETE M ~ G , CURING AND HANDLING AND CONCWTE TESTING
The Glass-Fly Ash Series and Powdered Glass Series concrete was mixed in a 0.07 m3 laboratory
drum mixer in batches ranging between 0.028 m3 and 0.064 m3 in accordance with ASTM C192
and C31. When used, air-entraining admixture was combined with the mix water; while
superplasticizer was added separately. As mixing was nearing completion, a small amount of
water was added to adjust the slump if necessary to achieve a target slump. Finally, the slump,
unit weight and air content were measured (ASTM C143, C138 and C231), and tensile and
compressive strength cylinders (150 mm x 300 mm or 75 mm x 150 mm), fieedthaw prisms (75
mm x 100 mm x 400 mm), and expansion prisms (100 mm x 100 mm x 250 mm) were cast as
appropriate for each batch. Strength and k e d t h a w specimens were moist cured according to
their respective standards (ASTM C39, C496 and C666). ASR expansion test prisms were moist
cured for 24 hours, then demolded and their original (1 day) length m u r e d ; moist curing was
then continued for 28 days before storage in a saturated lime water bath.
Mixing and sample preparation procedures for the field trials followed the previous laboratory
procedures as closely as possible; a 0.25 m3 drum mixer similar to the laboratory mixer was
used with a batch size of 0.17 m3 to allow careful control and adjustment of the mix.
Materials in the field trial were generally handled in a wet condition, and slump was used for
quality control rather than moisture per se, while moisture contents of the materials used were
measured for later use in analysis. Each batch had its slump, unit weight and air content
measured according to the same procedures as for the laboratory mixes. Tensile and
compressive cylinders, expansion prisms and freezelthaw prisms were cast and covered with
plastic for 24 hours, after which they were transported to the lab and demolded. The
specimens were then handled according to the same procedures as the laboratory specimens.
The Field Trial test sections were formed and placed by contractor personnel with
wheelbarrows and hand tools. Burlap was used to ensure continuous moist curing, which
continued for seven days following placing.
Mortar bar specimens (25mm x 25mm x 250mm) were cast according to ASTM C305 for the
accelerated ASR testing. They were moist cured for 24 hours before demolding, then stored
in 1N NaOH at 80°C for 24 hours before their initial length measurement, after which testing
proceeded in accordance with ASTM C1260 with storage in IN NaOH at 8O0C, and
expansions being measured at various ages up to 21 days.
Compressive strengths were measured at various ages fiom 7 to 365 days according to ASTM
C39. Prior to testing, the cylinders were capped with a sulfur-based capping compound (ASTM
C617) to provide a stable and uniform bearing surface. The cylinders were loaded in compression
until failure, with the peak load recorded; the load rate was held constant at 13 MPdmin. Tensile
strength was tested at various ages fiom 7 to 56 days according to ASTM C496; cardboard
bearing strips were used for the split-cylinder tension test with a constant load rate of 13MPdmin.
The original plan for the Glass-Fly Ash Series included ASR expansion measurements at ages of 1,
4, 7, 14, 28,90, 180, 270 and 365 days. The schedule outlined in ASTM C227, upon which the
concrete prism test was modeled, calls for measurements at ages of 1, 4, 7, 14, 28, 56, 112, 224,
and 448 days. These two schedules were combined in the actual research, resulting in
measurements being taken at ages of 1,4,7, 14,28,56,90,112,180,224,270,3'65 and 448 days,
to allow both direct comparison between Phase-I and Phase-I1 data and use of the ASTM standard
schedule. After the initially planned testing was complete, further measurements were recorded at
ages of 730 and 1095 days. To accurately measure the length of the specimens, a standard dial
gauge length comparator was used (ASTM C490), with a precision of 0.0001 in. The calibration
of the gauge was checked before and after each measurement, to ensure accurate operation.
Testing of freeze-thaw durability was done by monitoring the change in the dynamic modulus of
elasticity of the concrete with age according to ASTM C666 Procedure A for at least 350 cycles
of exposure for all of the experimental mixes and up to 600 cycles for some of the mixes. After
curing for 28 days, the initial dynamic modulus for the freeze-thaw testing program was measured,
at a temperature of 40°F. The length, width, depth, and weight of the prisms were measured, as
well as the fundamental transverse, longitudinal, and torsional fi-equencies according to ASTM
C215. A freeze-thaw rrrachine was used which kept the samples immersed in water and cycled
them between -18°C and 4°C at a rate of approximately 8 cycles per day.
The transverse fi-equency, for calculation of the dynamic modulus, was measured at various
intervals. Weights were measured at several times during the testing schedule, and interpolation
used where intermediate weights are required. The durability factor, an important indicator of
resistance to kze/thaw &gdabon (ASTM C666), may be calculated without considering the
weight of the specbn, however, the weight loss itself is a useful indicator of durability.
The Field Trial test sections were tested at ages of 7, 28, 120 and 365 days by non-destructive
testing using the rebound hammer (ASTM C805), by taking cores for compressive strength
(ASTM C42), and by visual observation of the test sections' general condition and resistance to
surface wear. The accompanying specimens cured in the laboratory were tested in compression
and tension according to ASTM C39 and C496 at ages of 7,28,120 and 365 days. Freeze-thaw
and ASR concrete expansion specimens corresponding to the field trial sections were cured and
tested according to the same procedures as earlier laboratory specimens.
In the results and analysis which follow in Chapters 4 and 5, the values shown on the plots are
average values of the several specimens at each cornbiition of mix parameters and provide
information to establish trends. A statistical approach was not used because of the small sample
sizes representing each combination of mix parameters (generally three to six specimens for each
distinct combition). Lines displayed in the plots unite the points of each experimental series for
clarity and do not represent a statistical fit of the data unless specifically discussed as such
As crushed waste glass, powdered waste glass and fly ash are posited as an aggregate replacement,
a cement supplement, and a cement replacement respectively, it is insightful to examine their water
demand for a constant workability. Any fine material used in concrete will exhibit a demand for
water to wet the surface area of the material and develop the electrostatic double layer necessary
for it to move easily within the k s h mix; Figures 4.1, 4.2 and 4.3 illustrate this relationship for
crushed waste glass, powdered waste glass and fly ash, respectively. The water demand is shown
on these plots as the w/(c +fl necessary to achieve a slump of 50 rnm; the variations in the actual
slumps of the experimental mixes were accounted for by adjusting the wl(c +fl by 0.01 per 5.17
mm of slump, determined by a linear regression (R~ = 0.96) of the control mixes with no glass or
fly ash.
The increased water demand due to glass rather than natural aggregate shown in Figure 4.1 is
clearly not linear, showing a characteristic shape for each series with a constant fly ash content
with a sharp discontinuity between 36% and 48% glass aggregate. This is probably because
during Phase-I the coarse aggregate fraction was changed from glass CA for replacement levels of
0% to 36% to glasses CC, CD and CE for replacement levels of 48% and 90%, and the fraction of
coarse glass aggregate used was increased &om 65% to 80% of the total glass aggregate (see
Table 3.4). Examining these glasses' effects on water demand in Figure 4.1 alongside their
gradations in Figure 3.1, it is clear that the Merence in gradation affects both the intercept and to
a lesser degree the slope of the water demand curve.
0% 15% 30% 45 % 60% 75% 90% Glass Content (% of Total Aggregate)
The increased water demand due to replacement of cement by fly ash is approxirnately~linear at all
levels of glass replacemnt, with some interaction with the glass being seen in a greater slope for
higher levels of glass replacemnt (i.e., in combination with 48% or 90% glass aggregate, the fly
ash itself exhibits a higher demand for water than when it is used in combination with 0% to 36%
glass aggregate).
The water demand of powdered glass (Figure 4.3) is low; a slight rise is observed with the addition
of small amounts of powdered glass followed by a downward trend up to additional levels of 20%.
The increased water demand by glass aggregate and fly ash shows its effect in the strength
developed by the various mixes, as will be seen in the next section. ,
FA F1,36% Glass
0% 5% 10% 15% 20% 25% 30% 35% Fly Ash Content (% of Total Cementitious)
0.42 0% 5% 10% 15%
Powdered Glass Content (% of Cement)
FIGURE 4.3. WATER DEMAND BY POWDERED GLASS CONTENT.
OBSERVATIONS DURING MIXING AND HANDLING
During mixing and handling, several observations of the behavior of glass aggregate were made:
Waste glass particles larger than about 3 mm were recognizable as pieces of broken bottles,
retaining the flat shape and smooth molded surface of the original glass bottles. Sharp fiacture
surfaces and edges were prevalent, making handling dficult and necessitating the use of heavy
gloves. Partial ffactures were visible in many of the particles, and all of the particles showed
noticeable fi-iability during handling and mixing.
Glass particles between 1.5 mm and 3 rnm showed some of the characteristics noted above,
while glass particles smaller than about 1.5 mm had notably different properties. Glass
produced by a commercial crusher and smaller than about 1.5 mm (e.g., Glass FG) was no
longer immediately identifiable as glass bottle pieces, instead resembling a sub-angular sand.
Photomicrographs of these glass sizes may be seen in Figures 1.1 through 1.6 in Chapter 1.
These glass sizes were much more easily handled, with no sharp edges and no noticeable
friability.
During mixing, placing and consolidating, similar observations were made of the poor shape of
the coarse glass pieces. The coarse glass pieces were extremely harsh, with the sharp edges and
protrusions creating a hazard requiring heavy gloves. The cement paste was not able to coat
the edges of the coarse glass particles because of the sharp convex vertices. All of these
characteristics were improved by using a gradation containing only fine glass, and still further
by using powdered glass. Malung comparisons between materials of similar fineness, i.e.,
gravel vs. coarse glass, sand vs. fine glass, and fly ash vs. powdered glass, the coarse glass
produced substantially harsher workability than similarly graded gravel, the fine glass produced
approximately the same or slightly harsher workability than similar sand, and the powdered
glass produced slightly better workability than similarly graded fly ash.
During the field trial, workers commented that the mixes with fine glass only were workable
and h h a b l e , but it was necessary to add some additional water to the surface of the pavement
to produce additional paste during finishing. The dryer mixes were judged d~fficult to
consolidate, but with work all were able to be consolidated by hand. Some of the core samples
taken fiom the sidewalk did display poor consolidation in the bottom layers.
The fly ashes generally performed as expected, providmg similar workability to cement, with the
exception of Fly Ash F3. Fly Ash F3 was more coarsely graded and contained many light
particles, causing bleeding and segregation of light particles and making finishing di6cult.
STRENGTH AND STRENGTH DEVELOPMENT
S~GTHOVERVIEW- LOW-ALKALIMIXES
An overview of strength results vs. wl(c +f) at ages of 28, 90, 180 and 365 days is iliustrated for
the low-alkali cement in Figures 4.4, 4.5, 4.6 and 4.7, respectively. The notation used in the
legend in this and other figures may be found in the Notation section before Chapter 1: the first
two letters indicating the type of coarse glass aggregate and the last two letters indicating the type
of fme glass aggregate; in those cases where percentages are given, the first is the amount of glass
aggregate as a fiaction of the total aggregate and the second is the amount of fly ash as a fkaction
of the total cementitious material.
The strength was adjusted for air content by 5% of the measured strength per 1% air content to a
nominal standard adjusted air content of 6.0%, with the non-air-entrained mixes assumed to have
2% entrapped air for the purposes of this calculation (Kosmatka and Panarese 1988). An
approximate trend line of strength vs. wl(c +f) of the form XI^'.^^"^^ for the control concrete has
been superimposed on each plot. For this equation, in accordance with Neville (1981), the - parameter Yis related to the composition of the concrete, particularly the type of cement, while X
54
varies with age. Y was thus fitted to all of the strength data for a moderate-alkd cement and low- - alkali cement, respectively, and then held constant for each cement at various a&. while X was
used to fit the data to each age. The strength characteristics of the various forms of glass
aggregate are evident from these plots.
The Powdered Glass Series at 28 days (Figure 4.4) has been adjusted for the different specimen
size (3 in x 6 in vs. 6 in x 12 in) as outlined by Nasser and Al-Maneseer (1987). They display
somewhat disappointing strength compared to sirmlar O/FG mixes, possibly because the ASR
activity was greater than anticipated and could not be mitigated by the powdered glass.
• 00100 OOFD a 0 0 m
,, A CC/FE o 00100 Field Trial + OO/FI Field Trial - Trend Line x OOIR Pwd Glass r 00/00 Pwd Glass'
+ +
m A
A a
A
A
1 I
FIGURE 4.4. Sl'RENCirT-l OVERVIEW - LOW-ALKALI CEMENT- 28 DAYS.
At an age of 90 days, the powdered glass series has lost further ground in strength development in
comparison to similar O/FG mixes (Figure 4.5).
00100
A CCIFE Q 00100 Field Trial + 00IFI Field Trial - Trend Line x O O m Pwd Glass 00100 Pwd Glass
+
+
A
1 A
A I I I
I I I 1
FIGURE 4.5. STRENGIH OVERVIEW - LOW-ALKALI CEMENT - 90 DAYS.
The most promising mixes with low-alkali cemnt are OOIFG and OO/FH; these mixes are able to
. perform as well or better than the control mix trend h e at ages of 180 and 365 days (Figures 4.6
and 4.7), and equally Important, are able to do so at wl(c +fi between 0.40 and 0.43 - within the
typical range of wl(c +fi for pavemnt concretes. With strengths of about 30 to 35 MPa at 28
days and 45 to 50 MPa at 365 days, they should perform very well as pavemnt, which typically
attains strengths of 20 to 35 MPa at 28 days and 40 to 50 MPa at 365 days.
The mix OO/FE performs fairly well, but at a very high w/(c +fi ratio of 0.53 even with high-range
water reducer. Glass FE was ground in the laboratory and has a much flakier particle shape than
glasses FG and FH, thus demonstrating the detrimental effect that extremely poor particle shapes
may have. The other mixes with low-alkali ce,mnt in the Glass-Fly Ash Series: 00lFD and C E R ,
all perform poorly; with the mix CE/FC containing coarse glass aggregate not only performing
poorly at high wl(c + fi ratios, (22 MPa at 365 days at wl(c + fi = 0.5 I), but even with high-range
water reducer and a large decrease in w/(c + f) to 0.39, its strength changes little ifat all, thus
making its performance relative to control concrete with a similar w/(c +f) ratio even worse.
5 5 OO/OO OOFD ,
50 A OO/FE OO/FF 0 OO/FG o OO/FH A CC/FE o 00100 Field Trial
45 + OO/FI Field Trial -Trend Line
FIGURE 4.6. STRENGTH OVERVIEW - LOW-~KALI CEMENT- 1 80 DAYS.
60 OO/OO OO/FD
, I A OO/FE OO/FF 55 -
0 OOFG o OO/FH
5 0 A CC/FE 0 W/OO Field Trial + OO/FI Field Trial -Trend Line
FIGURE4.7. STRENGTH OVERVIEW - LOW-AKALI CEMENT- 365 DAYS.
57
The field trial specimens with h e glass aggregate FI, which is very similar to aggregate FG, are
somewhat-surprising in their results. The control mixes without glass and with fly ash, 0%/0% and
0%120%, perform fairly well - achieving strengths of 41 MPa and 56 MPa at wl(c + fl of 0.49
and 0.36 respectively after 365 days. The Merence between these two strengths is rather small,
however, considering the large Merence between the two wl(c + A ratios. The rest of the field
mixes (composition 00m) show a similar trend, with all of them performing moderately well, but
with remarkably little difference between those of low and high w/(c +A ratio.
I
..................................................................................................
T o A 7 Day Cores 1 '
. . . . . . . d ...................... 28 Day Cores .....................................
A f 365 Day Cores X A 7 Day Cylinders
.......................... ...................................
A f 28 Day Cylinders -
0 365 Day Cylinders I
A ..................................................................................... A . . . . . . . . . . . . . . . I
0.35 0.37 0.39 0.41 0.43 0.45 0.47 0.49 0.51 0.53
wl(c +f) FIGURE 4.8. CORE STRENGIHS AND PARAUEL LABORATORY CYLINDER STRENGTHS.
The strengths of the test cores taken from the sidewalk trial sections are shown in Figure 4.8 along
with the strength cylinders providing parallel strength data in the laboratory; both the glasdfly ash
composition and the fly ash type are shown along the top of the figure for each mix. The core
strength and cylinder strength data are fairly consistent along overall trends. The higher strength
of cores compared to cylinders is typical of a comparison between core and cylinder data
(Bungey 1979) and is due to differences between the specimen sizes. This pattern is not clear in
the early age data is likely due to less than optimal curing conditions at the site. AU of the trial
sections are performing well at an age of one year. The effects of the different fly ashes enters into
a comparison of the various mixes - the mixes with fly ash F3 have a much higher water demand,
but are nonetheless nearly as strong as the mixes with fly ash F2.
STRENGTH OVERVIEW - MODERATE-ALKALI MIXES
An overview of strength vs. wl(c + J) for the mixes with coarse glass aggregate and moderate-
alkali cement at ages of28 and 180 days is illustrated in Figures 4.9 and 4.10. The strength was
adjusted for air and a trend line of the form for the control concrete was fitted; both in
the same manner as described above for the low-alkali mixes. It may be seen that the coarse glass
aggregate concrete series follow the general trend of the control concrete, but fall consistently
below the trend line. Furthermore, the shortfall is greater with increasing age, with no concrete
achieving greater than about 27 MPa at 180 days, far short of the expected strength of pavement
concrete of 40 to 50 MPa. Comparison of these results for mixes with coarse glass aggregate and
moderate-alkali cement with those for coarse glass aggregate and low-alkali cement in the
previous .section suggests that the relatively poorer performance is primarily due the coarse glass
aggregate rather than the differences in the cements.
40 . . 00100 C+oo
CCFA 0 CDIFA
5 M A
= 20 - Q k A A
X m A
15 " - : A A A
0.49 0.52 0.55 0.58 0.6 1 0.64 0.67 0.70 w +f
FIGURE 4.9. STRENGTH OVERVIEW - MODERATE-FUCALI CEMENT- 28 DAYS.
. 00100
CCFA
-Trend Line
A . I
A
A P U
l l l l ' l l r n l / 1 1 1 1 , 1
0.49 0.52 0.55 0.58 0.61 0.64 0.67 0.70
wl (c +f) FIGURE 4.10. STRENGTH OVERVIEW - MODERATE-ALKALI CEMENT- 180 DAYS.
C)THER OBSERVATIONS
During the strength testing it was observed that the moderate-alkali mixes with coarse glass
aggregate produced a very flexible fracture with a large strain accompanying the failure. The low-
alkali mixes with fine glass gradations produced a fracture in most cases comparable to the control
concrete at similar ages. At 365 days, the kacture was along a very sharp failure plane in the fine
glass mixes, with numerous instances of coarse natural aggregate particle shearing. Fractured
coarse glass aggregate particles were observed in compression tests at ages of 90, 180 and 365
days.
Tensile strength experimentation was conducted in the hopes that it would shed light on the bond
between cement paste and glass aggregate or on the disruption of the concrete matrix by ASR.
The relationship between tensile and compressive strengths was not substantially different for
experimental glass mixes vs. control mixes, however, thus no further use was made of these results
in the analysis and discussion. The tensile strength data are included in the data compilation in the
Appendix 4.3.
DEVELOPMENT OF STRENGTH - LOW-ALKALT MIXES
The development of strength by the various mixes is shown for low-alkali cement in Figures 4.11
and 4.12, for the Field TriaI in Figures 4.13 and 4.14, and for the Powdered Glass Series in
. Figure 4.15. Low-alkali cement was also used in both the Field Trial and the Powdered Glass
Series. The differing effect of the several different types of fly ashes is obvious on these plots.
Mixes containing no glass and 25% fly ash F1 or F2 have their respective strength development
curves shown in Figure 4.12, while a mix containing 20% fly ash F2 is shown in Figure 4.13. It is
apparent that fly ash F1 develops its strength more quickly, while fly ash F2 develops a significant
portion of its strength only after 180 days of curing. The control concrete, on the other hand,
maintains a virtually constant slope (on a logarithmic-scaled plot) fiom 28 through 365 days.
6 1
The superior performance of the mixes 00FG and 00/FH is again evident in Figure 4.1 1; though
they start with somewhat lower strengths than the control concrete with HRWR, they have a
consistently steeper slope than either the 09610% controls or the 096125% control with fly ash.
Furthermore, as the fly ash induces a characteristic strength gain acceleration between 180 and 365
days, the mixes with glasses FG and FH, also containing 20% fly ash, follow a similar pattern, but
are again able to maintain a steeper slope than the 0%/25% fly ash mix. It may also be noted that
while the mixes with glasses FG and FH show similar results in the strength overview discussed
above, their strength development shows different trends at later ages, with mix O/FH showing
almost no increase in slope after 180 days, despite its 20% fly ash content. The primary difference
between these two mixes is that glass FG is well-graded and contains considerable fine material
(~25% finer than 200 pm), while glass FH is fairly uniformly graded at approximately 1 mrn and
contains much less fine material (4% finer than 200 pm). . .
5 5
50
45
h
$40 z 3 35 00 c 3 30 V)
25 - 24%/25%, OO/FG,
20 - 20%/20%, OO/FG,
15 - 20%/20%, OO/FG,
10 100 i I - 20%/20%, OO/FH, Age (days) HRWR
FIGURE 4.1 1. DEVELOPMENT OF STRENGTH - LOW-ALKALI CEMENT - FINE GLASS GRADATIONS.
The other mixes shown in Figure 4.1 1 all show a pattern of starting at a fairly low strength,
developing strength slightly more quickly than the fly ash control concrete up to 90 days, then
slowing down and developing approximately in step with the fly ash from 90 to 365 days. The
mixes with a both coarse and fine aggregate and fly ash F1, shown in Figure 4.12, show consistent
strength development, in line with both the 0%/0% control concrete and the 0%/25% control with
fly ash F1 and sornewhat slower than any of the fine-glass-only mixes.
10
10 100 1000 Age (days)
FIGURE 4.12. DEVELOPMENT OF S M G I H - LOW-ALKALI CEMENT- COARSE GLASS GRADATIONS.
. . . . . - 24%/25%, FA
- 24%/30%, FA.
. . . . . . . . . . . . . . . . . . .
. . , . . . . . . . . . . . . . . . . . . . . . . , , . . . . . . . . . . . . . , , . , .
. . . . . . . . . . . . . . , , . , , .
The developmnt of strength of the field trial mixes, both laboratory cylinders and core samples, is
shown in Figure 4.13 for the mixes with fly ash F2 and in Figure 4.14 for the mixes with fly ash F3.
The trend for every mix is that the laboratory cylinders develop a greater fraction of their strength
before 28 days, while the core samples develop a greater fraction of the strength after 28 days.
This is to be expected because of the optimal curing conditions for the laboratory cylinders. This
effect is greatest for the 0%/20% fly ash F2 mix, suggesting that the hydration as influenced by fly
ash may have been slowed down by the cooler fall weather several months after casting. Because
this effect is not as evident for any of the mixes containing glass aggregate, there may be some
cross-effect between glass aggregate and the development of strength by fly ash - thls interaction
will be discussed further in Chapter 5.
The strength development of the mixes in the Powdered Glass Series is shown in Figure 4.15.
None of the mixes in this series develop strength well, though the strength was only monitored to
an age of 90 days in this series. The control mixes with no glass aggregate exceed the strength of
all of the other mixes by a wide margin. Most all of the mixes containing powdered glass display
erratic strength development, with a dip in the strength development curve at some point in most
cases; all but the control and the 10% glass mix show a peak at some point in the curve, while the
2.5%, 5% and 20% mixes show both a peak and, later, a trough fiom which then subsequently rise
again. The erratic data observed here and the possibility of an effect of ASR on strength in the
Powdered Glass Series will be discussed in Chapter 5.
DEVELOPMENT OF STRENGTH - MODERATE-ALKALI MIXES
The development of strength is illustrated for moderate alkali cement with glass contents of 0%,
24%, 48% and 90% in. Figures 4.16, 4.17, 4.18 and 4.19, respectively. All of the mixes in these
series with glass aggregate contain both coarse and fine glass aggregate.
The 0%/0% control mixes and mixes with fly ash but no glass in Figure 4.16 show considerable
variability, but the fly ash mixes generally start with slightly lower strength than the control mixes
and develop strength faster over their entire curing time.
Looking over the range of glass mixes in Figures 4.17, 4.18 and 4.19, it may be noted that the
mixes containing glass all develop strength more slowly than the control mixes, and therefore
much more slowly than the fly ash-only mixes shown in Figure 4.16.
The pattern of strength deveiopmnt with coarse glass aggregate (mixes CWA) in Figure 4.19 is
sunilar to that found by Johnston (1974), who noted that as gravel is replaced by coarse glass,
there is a gradual move fiom normal strength growth to no growth or even regression of strength
as the percentage of glass increases. He found, for example, that the ratio of 365 day strength to 7
day strength decreased Iiom about 1.87 with no glass to about 1.08 with 100% glass coarse
aggregate. Our results are similar but less severe, with a ratio of 1.70 for a 0%/0% mix decreasing
to 1.37 for a 90%/0% mix. The CE/FC mixes fiom Phase-II in Figure 4.12 display a marked
difference in behavior compared to the Phase-I CAIFA and C W A mixes, with strength
development nearly equal to that of the control - a difference which may be due either to the
low-alkali cement or to the use of air entrainment in these mixes. ~ h k Phase-I. mixes with only
fine aggregate, especially gradation 00/FG, show the most impressive pattern of strength
development with a strength rise between 180 and 365 days even greater than that of the control
mix with fly ash, which does itself show a very substantial increase during that period.
40 . . . . . . . . . . . . . . , , . .
1 -0%10% - - O%/O% j -O%/O%
-.c 90%/0%, CCEA - : . . . . . . . . . . . . . . . . . . . -o- 90%RO%, CCEA . . . . . . . . . . . . + 90%125%. CCEA . . . . . . . . . . . . . . . . . . . . . . . . . . -+ 90%/30%. CCEA - . . . . . . , . . , , . . . . . . . , . . , , .
+90%/35%, CDEA 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . .
, . . . . . . . . . : : I , . . , . . . . . . . , . . , .
. . . . . . . . . . . . , . , . . ,
. . . , . , . . .
5 10 100 1000
Age (days) FIGURE 4.19. DEVELOPMENT.OF STRENGTH - MODERATE-AWALJ CEhENT - 90% GLASS.
RELATION TO GLASS CONTENT AND FORM
The relationship of strength to glass content and form may be seen in Figure 4.20, which has been
normahzed for a given mix as the ratio of the measured strength, adjusted to 6% air content, to the
trendline at the same w/(c + f) ratio (fiom Figures 4.7 and 4.10). This separates the effects that are
intrinsic to glass and fly ash fiom the effects of glass and fly ash on water demand. Notice first that
the strengths of the CAFA mixes show a large drop with as little as a 12% addition of glass, reach
a minimum at 24% to 36% glass, then rise slightly with additions of 48% and 90% glass. The
CE/FC mixes have strengths 4 0 % higher than the CAFA mixes, but being Phase-I1 mixes, this
may be due either to the difference in cement type or to the use of air-entrainment in Phase-I1 of
the Glass-Fly Ash Series (The strengths are adjusted for air content to account for the effect of
simply introducing voids into the matrix. If the air voids have an additional secondary effect, such
as the mitigation of microstructural damage by ASR, thls would still appear in the strength
relationship because the air content adjustment is based on separate control mixes).
There is a clear non-linear effect of glass on strength displayed in Figure 4.20, with a consistent dip
at the 24% and 36% aggregate levels with the coarse aggregate. An interaction with fly ash which
changes for varying amounts of glass aggregate is also seen, with the order of increasing strength
being 0% fly ash<(20%=25%=30%)<35% at 0% glass, reversing to 35%<(30%=25%)<20%<0%
at 36% glass, and back to 0%<20%<25%<30%<35% at 90% replacement of glass aggregate.
The markedly non-linear behavior, and the interaction between glass and fly ash evident fiom a
comparison of the different curves displayed in Figure 4.20, suggests that there may be more than
one distinct effect of glass aggregate that is contributing to loss of strength - this will be
discussed at more length in Chapter 5.
The OOEb mixes, on the other hand, display substantially better behavior in Figure 4.20, with
normalized strengths between 0.87 and 1.13 at glass contents of 20% to 24%.
0% 15% 30% 45% 60% 75% 90% Glass Content (% of Total Aggregate)
The effects of fly ash content and form are illustrated in Figure 4.21. These strength results have
been normalized to the trendlines in Figures 4.7 and 4.10, i.e. the normalized strength is the ratio
of a given mix's strength to the strength of the trendline at the same wl(c +J) (long-term 180- and
365-day results are included in this figure). It may be noted that the field trial mixes (all 00m)
show a fairly strong effect of fly ash F2 vs. fly ash F3, confirrmng the observations inade in the
general overview of strength results, though there is a wide variation within each fly ash: fly ash F2
produces normalized strengths of 1.61 and 1.12 while fly ash F3 produces normalized strengths of
0.90 and 0.62.
-
- O%/y%, 00100, FA F2 20%1y%, OOIFG & OOIFH, FA F2
4 24%1y%, OOIFE & OOFG, FA F3 13,%/y%, CEFC, FA F1
4 24%Iy%, -CEFC, FA F I A 36%1y%, CEIFC, FA F I A 0%/0%, 00100, Field l'rial
x IO%/y%, O O F I , FA F3, Field x 20%1y%, OOFI, FA F2, Field
+ 20%1y%, OOFI, FA F3, Field - O%/y%, CAIFA, FA F I
12%1y%, CAIFA, FA F I o 24%1y%, CAIFA, FA F1
RELATION TO POWDERED GLASS CONTENT
The relation of strength to powdered glass content is presented in Figure 4.22. The strengths are
normalized for air content according to the procedure described earlier - note that the entire
Powdered Glass Series was conducted at a constant wlc ratio of 0.43, therefore no adjustment for
WIC variation is needed. AU of the strengths relative to the control mixes are below the strengths of
comparable glasdfly ash mixes that performed well in the GlassFly Ash Series; this may indicate
either that the addition of powdered glass impairs strength overall, or it may indicate an ASR
reaction is taking place that is disrupting the concrete matrix and reducing the strength. Because
the reduction in strength appears already with glass aggregate and no powdered glass addition, and
because the reduction in strength does not increase with higher additions of powdered glass, but
rather seems to reach an extreme value at 5% addition at all ages, it is more probable that the
0.40
observed effect is due to an ASR reaction.
A 36%ly7o, CA/FA, FA F I
0% 10% 20% 30% o 48%/y%, CC/FA. FA F I Fly Ash Content (% of Cementitious) . 90%1y70, CCIFA, FA FI
FIGURE 4.2 1. RELATION OF STRENGTH TO FLY &H CONTENT AND FORM.
0% 5% 1090 15% 20% Powdered Glass Content (9% of Cement)
,PATERNS OF STIFFNESS DEGRADATION AND WEIGHT LOSS
The progressive degradation of stiffness over the course of the fieeze-thaw tests is shown in
55
5 0
h a
45 w
Figure 4.23 for the glass mixes with both coarse and fine glass, and in Figure 4.24 for the glass
mixes with fine glass only. There is no firm criterion of acceptable performance, but the author's
experience suggests that a mix must retain 80% of its original stiffness after 300 cycles of exposure
for it to be acceptable for use in pavement.
I
4 -
- 20% Glass Aggr. w/ & w/o Powd. Glass -- 28 Days -1- 2090 Glass Aggr. w/ & w/o Powd, Glass -- 56 Days - - * -. 20% Glass Aggr. w/ & w/o Powd. Glass -- 90 Days
0 No Glass Aggr. w/o Powd. Glass -- 28 Days o No Glass Aggr. w/o Powd. Glass -- 56 Days 0 No Glass Aggr. w/o Powd. Glass -- 90 Days
The pattern established by the control mixes is for the stiffness to drop immediately (within 10
cycles) to approximately 93 to 96% of the original sthess, 'then for the specimen to retain that
stiffness nearly constantly through the entire test: the 0%/0% mix initially drops to 94.5%, and
maintains that through the remainder of the test, while the 0%/0% control with HRWR initially
drops to 94% and loses only 2.5% between 10 cycles and 600 cycles.
-
-
I t
100 Cycles
85
10 100 1000 Cycles
FIGURE 4.24. FkEEZE-THAW STIFFNESS DEGRADATION - FINE GLASS GRADATIONS
-
IL
...........
............................................................................ >- ...........
-O%iO% - 24%/25%, 00/FE, HS- . - 20%/20%, OO/FG. HRWR - 20%/20%, OO/FG, MRWR - 20%/20%. 00/FH, HRWR - *0%/0%, HRWR
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.............................
Among the coarse glass mixes (Figure 4.23), the only mix showing a sirmlar pattern is the
12%/20% mix, which initially drops to 95%, then loses an additional 2% between 10 cycles and
350 cycles. In contrast, the other coarse glass mixes lose between 9% (mix 20%/25%) and 22.5%
(mix 24%/30%) from 10 cycles to 350 cycles, after an initial drop which is very similar to or even
less than that exhibited by the control mixes.
The h e glass gradations FG and FH, on the other hand (Figure 4.24), show degradations between
10 cycles and 600 cycles of 4% for gradation FH, compared to degradations of 2% and none for
the two FG mixes, respectively. The FE gradation shows a degradation of 6.5% between 10
cycles and 350 cycles, reflecting its hgh wl(c +A ratio and low strength.
100 Cycles
. . . . . . . . . . .
. . . . . . . . . . . . . . ......................................
............ ...............
....................... -o-- 12%/20%, cE/Fc ..................... - 20%/25%, CE/FC - 20%/30%, C W C - 36%/25%, C W C
The weight degradation experienced by the test specimens over the course of the freeze-thaw
testing is illustrated in Figures 4.25 and 4.26. All of the prisms show a similar pattern, with the
differences appearing in the magnitude of loss rather than showing a distinctly different pattern
between successful and unsuccessful specimen's. The control specimens show better results than
any of the experimental mixes, with weight losses of =I% at 350 cycles.
The coarse glass mixes, shown in Figure 4.25, are tightly grouped at 2.5 to 3.5% loss at 350
cycles. The 12%/20% mix, though the leader among the coarse glass mixes with 2.5% loss at 350
cycles, is still worse than that of the control mixes, in contrast to its fairly good stfiess retention
(Figure 4.23).
The fine glass mixes, shown in Figure 4.26, show wider variation, and while still following the
same trends in weight loss as for stfiess, some of the weight losses are several times that of the
control mixes. Gradations FG' s performances with weight losses of 1.5% and 2.5% at 350 cycles
correspond well to their 10 to 600 cycle stiffness losses of zero and 2.5%. Gradation FH's
performance also corresponds well (4% loss in stiffness between 10 and 600 cycles, 2.5% loss in
weight at 350 cycles). Gradation FE's relatively poor performance (6.5% loss of s tf iess between
10 and 350 cycles - about 3-4 times the best performing fine glass mixes) is further highlighted
here, with a loss of 4.5% of its weight at 350 cycles.
O % / O %
_- - 20%/20%, OOIFG, MRWR
- nO%/O%, HRWR ............,...................................................
100 Cycles
The s thess degradation of the field trial specimens is illustrated in Figure 4.27. hey maintain
excellent stfiess through about 70 cycles, but between 70 cycles and 350 cycles, there is an
alarming degradation. Using a criterion of 80% stffhess retention at 350 cycles, the two Fly Ash
~ 2 ' experimental mixes (20%/25% and 20%/20%) fall below this limit; and while the Fly Ash F2
0%/20% control mix does not fall below the experimental mixes, it does show a similarly steep
degradation between 200 and 350 cycles. The superior fi-eeze-thaw performance of the Fly
Ash F3 mixes along with the superior strength performance of Fly Ash F3 points to a clear
difference between the two fly ashes. The pattern indicated by the stfiess degradation in the
fi-eeze-thaw tests is that the combination of glass and fly ash in concrete clearly does reduce freeze-
thaw stfiess durability substantially, though the cause of the dramatic loss of s t he s s between 70
and 350 cycles is unexplained and may be an artifact of this particularly test series.
100 Cycles
. . . . . . . . . . . . . . . . . . . . . . . . , . . . , , . , . ..... ..,.... ' ..,.
.. :. ... :. .. :. . .:. . .:. . :. . . . . . . . . . . . . . . . . . . . . . . , , , . , . ..y
. . . . . . ......... , ............. .... ::; i . . . l . . . : . . . : . . i . .
... ....,....... ..... ..,.. . . . . . . . . . . . . . , ... , .......... , .. . . . . . .
..................... . . , . , . . . . . . . . > . .
..................... , . . . . . . . . ....................... . . . . . . ........... , .......... , . . . . . . . . . . . . . . . :............. :..... ............. . . I . . ...... .. ..... :....:...:...I.. .:.. .\>. ..> \:. :. :;+. . ;. ... : . . . ; ...;..;..... . . . . . . <. ' ......................... C . . . . . . . . . . a ...,.......................... %::::. .. .\. .'. ...... ' . ................ . . . . . . .............................................,........ . , , , . . .............. ...... , ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... .......................... ...... : .... :...-....\.:.. :.................. ..\ ..,.. + :...:...:...:. .: . . . . . .
, , . , . , . -. , . . . . . . '.*" ................,.. ....................>... , ....................... .......... , . . . . , ................. . . * . . . O % / O % . . , , , . ........................... .:. ... .\?; .:. ............................ . . , . . .. .:. . .. ., ..,................... ..:.. . . ..\ 1:. . . . . . : . .: .;.. .:. .;. . . . . . -- - - 20%/20%, FA F3, HRWR : : : ..
. . . . . . . . . . . . . ............ L .............. :. ...... .\::I .... : : : .:. .:. : . . . . . . . .-*.- ..-, .........-...... ....... . --.... . . . . ........ 10%/15%, FA F3, HRWR .. .; . .:. . .:. .:. .,. -. , , ..,..
. . . . . . . ..:.... ....................................... . \ . . r . . : : , .:.. . . . . . . . . ...................................... - - -.- - 20%/25%, FA m, HRWR .. .! . .: . .I.. ............... :. \ . , , , , . -
...... . . . . . - -a - 20%/20%, FA n, HRWR ...:. . .:.. ................... . i . . .:. .e. . i.. . ; . i . . .I. : . I . . :. ....................................................................
....... .......... . . ... , ............ . : : ~ . - ~0%/'20%, FA F2, HRWR .. .; . . . . .:. ................ .:. .:. , , . . . . . . ........... '.. ................................ L I _ _ _ > . .........I.. . . . . . . . . . . . .
FIGURE 4.27. FREEZE-THAW STIFFNESS DEGRADATION - FIELD TRIAL.
I See pages 42-43 for definition of fly ash types F1, F2 and F3.
7 6
Figures '4.28 presents the stiffness degradation of the Powdered Glass Series. Because the
Powdered Glass Series included control mixes with both 4.2% and 8.1% entrained air, it is
possible to make some observation of the effects of entrained air on keeze-thaw durability: the
prisms with 8.1 % entrained air drop slightly more during the first 10 cycles (a drop of 7.8% vs. a
drop of 5.3% for the control mix with 4.2% entrained air), but degrade less during the remainder
of the test (3.4% degradation between 10 and 350 cycles vs. 8.9% for the 4.2% entrained air mix).
The 20% powdered glass prisms fail to maintain substantial stfiess, with only 46% of the
stiffness remaining after 350 cycles, but it is not clear whether this is due to the presence of
powdered glass or because of the 3.4% air content. The other mixes have varying performance,
with the 1% and 2.5% powdered glass mixes somewhat better than the control mixes and the rest
somewhat worse, as illustrated in Figure 4.29.
100
95
90
10 100 loo0 Cycles
R G u ~ ~ 4 . 2 8 . FREEZE-THAW STIFFl\TESS DEGRADATION - POWDERED GLASS SERIES.
I 0 . 4 20% Glass Aggr. ~n 40% -- I
*. Control wlo Glass Aggr., 'b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c cd
0 -i 30% e -
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 20% a -
C I .
(A
0% 5% 10% 15% 20% Powdered Glass Content (% of Cement)
FIGURE 4.29. STIFFNESS LOSS BETWEEN 10 AND 350 CYCLES BY POWDERED GLASS CONTENT
The trend which is seen in Figure 4.29 suggests an optimal powdered glass content of 1 - 2.5%,
and the trend of increasing degradation with 10 - 20% powdered glass suggests that both low air
content and high powdered glass content contribute to the poor performance of the 20%
powdered glass mix.
OBSERVATIONS OF SPUG AND Q U ~ A T Z V E BEHAVIOR
Visual observation of the degradation during the freeze-thaw testing suggested that the majority of
the degradation took place in the mortar fraction of the concrete. Paste sloughed predominantly
from the glass aggregate particles, either h e or coarse, with subsequent sloughing of the glass
particles themselves as the degradation continued. The comers of the specimens, which had a
higher mortar content because of the edge effect of aggregate paclung, were noticeably weaker
than the face of the specimen after freeze-thaw exposure.
Based on visual assessment, the Field Trial test sections have shown excellent durability to - abrasion and freezing weather. . Only a small amount of paste has been removed from the top
surface, exposing the top layer of both natural and glass aggregates. The top layer of aggregate
appears to remain well bonded in the pavement, including the glass aggregate. Additional wear in
the wheel tracks is minimal.
ALKALI-SILICA REACTTVITY AND DURABILITY
OVERVaY OF CONCRETE PRISM EXPANSION AND RELATION TO GLASS CONTENT AND TYPE
The effect most distinctive of g h s aggregate and of most concern in this research is the
development of the alkali-silica reaction between glass aggregate and cement paste - detected by
monitoring the expansion of concrete prisms. Concrete prism expansions versus glass content at
ages of 28, 365, 730 and 1095 days are summarized in Figures 4.30, 4.31, 4.32 and 4.33,
respectively. The expected pessirnum behavior, wherein the expansion is a maximum at some
intermediate glass content, is evident in these figures with a pessimum content of 36% to 48%
glass for the moderate-alkali mixes; it is most clear at early ages (e.g., at 28 days, the expansion of
the 36% glass prisms is more than double that of the next highest prisms), but is still somewhat
evident even at an age of 1095 days. Figures 4.30, 4.3 1 and 4.32 also show a pessimum effect
with the low-alkali mixes; however, it appears at a glass content of 20% to 24% in thk case.
There is also a pessimum-like- effect in the strengths illustrated in Figure 4.20, with the lowest
strengths being recorded at a glass content of 24 - 36%; this suggests that there may be some
interaction between ASR and strength development with glass aggregate - this will be discussed
in Chapter 5 as an interaction between glass and fly ash.
Failure criteria have been defined at the various ages for the low-alkali mixes, the Field Trial mixes,
and the moderate-alkali.mixes according to guidelines suggested by Rogers and Hooton (1991).
They suggest that no absolute criteria may be established to differentiate acceptable fi-om
unacceptable expansion during a long-term concrete prism test; rather, the expansion of a known
innocuous control aggregate without fly ash should be used, with a small additional margin to
allow for slight variations in aggregates and measurements and to allow for other effects which
might cause small changes in concrete prism dimensions over time. A margin of 0.005% over the
expansion of the control mix at each age has been used as the criterion in this analysis. Rogers and
Hooton notes that thls method of establishing fdure criteria is reasonable because most all
aggregates develop some slight ASR, and if fly ash is effective in mitigating ASR it should
substantially e h a t e expansion, not slmply reduce it to a slightly lower level.
. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - , 'b.*.-.## . . . . . . . . . . . . . . . . . . # . , # # . # . . . . . # .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C . . . . . . .
. . . . . . . I,, . . . . . . . . . . . . .
. . . . . . . . . . . . . - 0 . . . .+-. .: ---.- I - - -- . - r - .- - - .r- - --JL77 :
-
Low,NoFA Low, 20% FA Low, 25% FA Low.30Yo FA - ' Low-Alk Criterion
B Field, No FA Field, 15% FA Field, 20% FA Field, 25% FA - - Field Trial Crirerior.
o Mod, N o F A 0 Mod.'O%FA A Mod, 25% FA o Mod, 30% FA + Mod, 35% FA - Mod-Alk Criterion
1 8 t
0% 12% 24% 36% 48% 60% 72% 84% 96% Glass Content (% of total aggregate)
FIGURE 4.30. CONCRETE PRISM EXPANSION BY GLASS CONTENT - 28 DAYS.
0% 12% 24% 36% 48% 60% 72% 84% 96% Glass Content (7% of total aggregate)
FIGURE 4.3 1. C O N C R E ~ PRISM EXPANSION BY GLASS CONTENT - 365 DAYS.
Low,NoFA Low,20%FA
A Low, 25% FA Low, 30% FA
- *Low-Alk Criterion Field, No FA Field, 15% FA Field, 20% FA
A Field, 25% FA . - Field Trial Criterion o Mod, No FA o Mod, 20% FA A Mod, 25% FA o Mod, 30% FA + Mod, 35% FA
h
5 loo 0 0
1000 .
A
t3 - 100 0 9 2 V
c
1
0% 12% 24% 36% 48% 60% 72% 84 % 96% Glass Content (% of total aggregate)
FrGURE4.32. CONCRETE PRISM EXPANSION BY GLASS CONTENT- 730 DAYS.
. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . .
C
. . . . .
. . . . . . . . . . . . . . E
. . .
I
. . . J
. . . .
. . . . . . . . . .
. . . .
. . . .
. . . .
0 9 , . .
. . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I 1 . . . . . .
. . . . . . . . . . . . . .
. . . . . . . . . . . . .
. . .
. . . . . . . . . . . . . .
. . . .
, I '
.....................................
c .................................................. ..................................................
............ 1.
....................
-. .-
I D - .+
- V ~ 9 , ~ ~ I ~ ~
. . . .
. . . . . . .
. . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .
. . .
1 - Mod-Alh Cri~erion & i " F , ' , >
F-- - e 4 - -6$- -
...................................................................................... ....................................................................................... ......................................................................................
.......................................................................................
..............................................................
.: . . . . . . . .
. . . . . . . . . . . A
. . .
-. . . .
. . . . . . - . . . . W + . . . . . . . . . . . . . . . . . . . . . A . .
....................................................................................................
.....................................................................................................
..............................................................
..............................................................
............................................................ ..................................
6 . . .- Bc
.............................................................. ..............................................................
..............................................................
..............................................................
..............................................................
..............................................................
..............................................................
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .
. . t . . . . . . . . .
.............................................................
. .
b . . . . . . . . . . . .
Low, No FA Low,20%FA
. . . .
. . . . . .
...........
. . . . . . . . . . . ........... 0 " - " : : 1:. . . - - . .
...........
........... " - "4- - - -
- . . . - . " o Mod, NoFA - .n. .-
A
T D
o Mod, 20%FA . . . . . . . . . . . . . . . . . . . . . . A Mod,25%FA . . . . . . . . . . .
...........
o Mod,30%FA ::::::::::: + Mod, 35% FA . . . . . . . . . . . - Mod-Alk Criterion - . . ' ' ' ' ' "
I s ~ 1 8 b 1 "
A LOW, 25% FA Low, 30% FA - .Low-Alk Criterion .......................................
o
. . . .
8 1
Among the low-alkali mixes, the 25%/30% CE/FC mix and the 20%/25% CEIFC mix have
slightly exceeded their limit by an age of 730 days, indicating that the combination of low-alkali
cement and air-entrainment do much to reduce ASR, but are not able to completely mitigate ASR
with coarse aggregate, even with some fly ash.
Only the moderate-alkali, coarse glass mixes have reached an age of 1095 days. At thls age, the
overall expansion trends continue, with mixes with fiom 12%/0% to 90%/0% exceeding their limit
considerably, and all of the 90% mixes exceeding their limit except 90%/30%, whlch is very near
the lint;
A pessirnurn phenomenon is clearly evident among the series of mixes with moderate-alkali
cement, no fly ash, and varying amounts of glass aggregate. The maximum reaction appears here
at a pessirnum content of about 36%, with the 36%/0% mix showing the highest expansion at
every age. As fly ash is introduced, however, the greatest expansion shifts to the mixes with 90%
glass, particularly the 90%/20% mix.
1
0% 12% 24% 36% 48% 60% 72% 84% 96% Glass Content (% of total aggregate)
FIGURE 4.33. CONCREIE PRISM EXPANSION BY GLASS CONTENT - 1095. DAYS.
.
I
.........
0
.+
.....................................
................................................. ...............................................................
...................................................
....................................................................................... .........................................................................................
....................................................................................................
........................
] , , I , , / , ,
...........................................................................
....................................................................................................
0
A . . . .
. . . . . . . . . . . "
............................................................................................... 0
...................................................................................................... ..................................................................................................... ..................................................................................................... .....................................................................................................
.....................................................................................................
0
D .A+ ..............
D
.........................
0 Mod. NO FA Mod,20%FA
A Mod, 25% FA . . . . . . . . . . . : ............
::::::::::::
Do t
A
............................................................... ............................................................ ............................................................. : ..............................................................
...............................................................
...............................................................
...............................................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.....................................
o M O ~ , 3 0 % ~ ~ + Mod, 35% FA
-Mod-Alk Criterion
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
The form and gradation of the glass, meanwhile, does not appear to have a clear effect on the
expansion. Looking at expansion after 365 days (Figure 4.31), it is difiicult to clearly differentiate
the effects of glass gradations, cement alkali level, fly ash type, and air entrainment, as they are
somewhat intermingled within the low-alkali and field trial series, but it is clear that the mixes with
a given fly ash content and glass content are fairly tightly grouped despite all of these variables.
These mixes will be examined more closely in the next section to separate the effects of some of
these variables. Overall, their is little variation in expansion between the Phase-I, Phase-LI and
Field T@ prisms containing both glass and fly ash.
Tables 4.1, 4.2, 4.3 and 4.4 summarize the performance of the mixes relative to their respective
criteria at ages of 28,365,730 and 1095 days, respectively.
TABLE 4.1. ASR PERFORMANCE AT 28 DAYS ('OK' IS ACCEPTABLE, '----' IS UNACCEFTABLE).
Moderate-Alkali Mixes
FA
0%
Field Trial
0% 12% 24% 36% 48% 90% Gls Gls Gls Gls Gls Gls OK ---- OK ---- ---- OK
Low-Alkali Mixes
0% 10% 20% Gls Gls Gls OK
0% 12% 20% 24% 36% Gls Gls GIs Gls GIs OK
TABLE 4.2. ASR PERFORMANCE AT 365 DAYS ('OK' IS ACCEPTABLE, '----' IS UNACCEPTABLE).
1 Moderate-Alkali Mixes I
FA I 0% 12% 24% 36% 48% 90%' 0% 10% 20% GIs GIs Gls Gls Gls Gls Gls Gls Gls
0% 12% 20% 24% 36% Gls Gls Gls Gls GIs ----
0% OK ---- ---- ---- ---- ---- OK
0% 12% 20% 24% 36% GIs Gls Gls Gls Gls
TABLE 4.3. ASR PERFORMANCE AT 730 DAYS ('OK' IS ACCEPTABLE, '----' IS UNACCEFTABLE). '
Field Trial
Moderate-Alkali Mixes
Low-Alkali Mixes
Low-Alkali Mixes
TABLE 4.4. ASR PERFORMANCE AT 1095 DAYS ('OK' I S ACCEPTABLE, '----' IS UNACCEPTABLE).
Moderate-Alkali Mixes
OK OK. OK OK OK ---- I
ACCELEFXM ASR SERIES RESULTS
Figure 4.34 presents the results of accelerated ASR tests (ASTM C1260) for varying amounts of
glass aggregate with no fly ash or powdered glass for mitigation. An expansion at 14 days of
0.12% has been used as a failure criterion. The natural aggregate used in the research is itself
slightly reactive, with results just below the 0.12% criterion with a mix of 0% glass and 100%
natural aggregate. As the proportion of glass used is increased, the expansion increases steadily to
a maximum at 40% - 50% glass aggregate - the pessimum content for this case - followed by a
gradual decline with lower expansions, but still 3 - 4 times the 0.12% criterion with a mix of 100%
glass and 0% natural aggregate.
0% 20% 40 % 60% 80% 100% Glass Content (% of Total Aggr)
FIGURE 4.34. A C C ~ T E D ASR EXPANSION - GLASS rn NO M~IGATION.
The effects of various mitigating admixtures are shown in Figure 4.35, which shows the change in
expansion as powdered glass or fly ash is added in various proportions. Mineral admixtures in
proportions of ~ 2 0 % or greater provide excellent mitigation of ASR expansion, with none of the
combinations containing at least 20% admixture expanding beyond the 0.12% criterion.
Comparing the curves for 20% glass aggregate and 40% glass aggregate, it may be seen that the
amount of glass aggregate used does have a signiiicant effect on the results of the test - 40%
glass aggregate produces approximately twice the expansion at any proportion of powdered glass.
The three admixture represented in the figure may be ordered (Fly Ash F2 > Powdered Glass >
Fly Ash F3) in their effectiveness at reducing expansion.
0% 5% 10% 15% 20% 25% Powdered Glass Content (% of Cement)
or Fly Ash Content (% of Total Cementitious) FIGURE 4.35. ACCELER4?ED ASR EXPANSION - FLY ASHES F2 AND F3, POWDERED GLASS.
-
400
E350 . . . . . . . . .
t ................................
\
I \ ........... .".
I 1
0 0 6 300 - X w
z250
200 d 4
% 150 c 0
'5; 100 c cu ? 50 W
0
.................. - 40% Glass Aggr. wffowd. Glass -a- 20% Glass Aggr. wffowd. Glass
\ " ' 1 1 \ \ \
-
-
-- .0.12% Expansion Criterion - - 0 . - 10 - 20% Glass Aggr. w/FA F2 - +- 20% Glass Aggr. w/FA F3
.
-
\ \ ................\......................
\
.....................\........
. . . . . . . . . . . . . . . . . . . . . . . . . , - - - - - -
. . . . . . . . . . . . . . .................................... ,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
- - - - - I
. . -.- . ..--. " ' -.
. . . . . . . . . . . . . . . . . . . ........
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I[ 8
8 . \ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
YL ............................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
b--
.T.-:.,, --.-.-. . . . . . . . . . . . . . . . . . . . . . . . . . . . . - - - - - -___
.................... ......,............ !
I
CHAPTER 5 - ANALYSIS OF DATA AND DISCUSSION
Glass aggregate produces significant effects across a broad spectrum of concrete properties,
including the fresh mix properties, strength, freeze-thaw durability, and ASR studied here.
STRENGTH
A range of strength behavior was observed among the various mixes containing waste glass,
with strengths at 180 to 365 days from less than 10 MPa up to greater than 50 MPa.
The most successful combinations were obtained for intermediate proportions of both glass
aggregate and fly ash. The 20%/20% OOIFG mix was among the strongest overall. Among
the coarse glass mixes, the 24%/25% mix seemed to be the optimal proportions, though the
particle shape and gradation of the coarse glass prevented it from doing as well as the optimal
fine glass mixes.
Several factors caused low strength among certain mixes:
Sugar or other chemical contaminants, where present, consistently reduced the strength by
as much as 40%.
An interaction between fly ash and glass reduced the development of strength by fly ash in
certain mixes.
Excessive use of some gradations of glass demanded such high quantities of water that the
concrete was beyond the range of w/c ratios for good quality concrete.
Use of poorly graded and poorly shaped glass hampered workability to the extent that
either the glass was not able to be consolidated or so much water was used to ensure
88
consolidation that the combined effects of high wlc ratio, bleeding, and segregation
severely hampered strength development.
Lower grade fly ash with high free carbon and sulfur trioxide contents, especially in
combination with glass aggregate with which it has several interactions, interfered with the
actions of water reducers and air-entraining admixtures to the extent that the overall
quality of the mix was reduced.
CAUSES OF STRENGTH REDUCTION AND VARIATION
The effects of waste glass aggregate on strength may be divided into four catagories:
1) Waste glass aggregate displays a water demand greater than that of natural aggregate.
Satisfaction of this water demand increases the WI'C ratio of the resulting concrete,
thereby producing a lower strength.
2) Waste glass aggregate reduces the strength developed by fly ash in the cementlfly ash
mix in situations in which ASR is active. This effect may reduce the strength of
concrete mixes made from typical proportions of glass and fly ash by as much as
10% - 20%. Possible reasons for this behavior are discussed in the next section.
3) The strength of the glass aggregate itself, its friability and relatively low resistance to
aggregate fracture, may be a factor limiting the strength of some concretes.
4) There is a strength loss intrinsic to the waste glass aggregate, i.e., it cannot be
accounted for by either a change in wlc ratio or air content, or a change in the behavior
of the cementitious components of the mix. This effect is probably due to a difference
in paste-aggregate bond for a glass particle versus a natural aggregate particle. The
variation in strength due to this can range from a 25% strength loss to a 5% strength
gain.
Table 5.1 presents an overview of how the effects of glass aggregate on strength break down
for several representative mixes. For purposes of comparison, strength effects shown in the . .
table and discussed in. Chapter 5 are displayed to the nearest 1%, though in practice strength
cannot be reproduced with that precision - in Chapter 6 the conclusions are discussed with
consideration for the precision achievable in practice. The values in Table 5.1 have been
developed as follows:
The strengths given in the table (MPa) are the long-term (6- to 12-month) strengths of the
respective mixes, adjusted to a nominal air content of 6% as described at the beginning of
Chapter 4; no other adjustments were made. The total effect then indicates how much the
experimental mix falls short of the control strength, as a fraction of the control strength.
This total effect is then broken down in the three intermediate columns into the effect of
water demand, the effect of the interaction of glass on the strength development of fly ash,
and the effect intrinsic to the glass aggregate.
The effect of water demand is calculated from the trendline displayed in Figures 4.7 and
4.10. The change in strength of the trendline between the wl(c +J) of the control concrete
and the wl(c +J) of the experimental concrete was taken as the effect of the water demand.
The effect of the interaction of glass on the strength development of fly ash was calculated
from the strengths which had been adjusted for wl(c +J) (illustrated in Figure 5.3). The
change in strength from 0% fly ash to the actual fly ash content for the control concrete
was compared to the corresponding change in strength of the appropriate glass series for
the experimental mix; the difference was taken as the effect of the interaction.
The magnitude of the intrinsic effect was then determined as the remaining difference
between the total effect and the effects of water demand and interaction, so that the three
components sum to the total effect. The intrinsic effect as defined here is primarily
assumed to reflect the bond between the glass aggregate and the cement matrix, as
discussed above, but may also include the effect of the strength of the glass aggregate
particles themselves as well as any other intrinsic effects that have not been hypothesized.
Total Effect
TAEILE 5.1. COMPONENTS OF STRENGTH EFFECTS.
Several conclusions may be drawn from the analysis presented in Table 5.1 :
Expr. Conuol Mix Mix
The effects of water demand increase steadily with increasing glass content, with the fine
glass (mixes OOIFG) exhibiting slightly lower demand than the coarse glass mixes.
Control Expr. Strength Strength (MPa) (MPa)
Effect of Effect of Lntrinsic Water Interaction Effect (Bond) Demand
12%/0% O%/O% CNFA NoFA
12%/25% 0%/25% CNFA FA F1
36%/0% O%/O% CNFA NoFA
36%/25% O%lO% CNFA FAFl
90%/0% O%/O% CNFA NoFA
90%/25% 0%/25% CNFA FAFl
24%/0% O%/O% CA/FA NoFA
24%/25% 0%/25% CNFA FA F1
24%/25% 0%/25% C E R FA F1
24%/25% 0%/25% OO/FG FA F2
20%/20% 0%/25% OOFG FA F2
39.5 26.8
42.2 20.2
39.5 22.5
42.2 15.1
39.5 11.0
42.2 9.9
39.5 23.2
42.2 17.1
42.2 22.4
52.5 45.4
52.5 53.0
-6% 0% -26%
-4% -20% -28%
-14% 0% -29%
-18% -24% -22%
-37% 0% -35%
-45% = -5% -37%
-1 4% 0% -27%
-8% -20% -32%
-8% -7 % -32%
G 0% -7% -6%
-5% -7% +13%
9 1
The effect of the interaction with glass on fly ash is substantial for all of the rnixes with
coarse glass and moderate-alkali cement, and increases slightly bemeen 12% and 36%
glass before dropping to near zero for 90% glass. For the mixes that include low-alkali
cement and air-entrainment (mixes CE/FC and OOJFG), the magnitude of this effect is
much lower, indicating that the change in cement is most probably responsible for the
difference, rather than the change in aggregate. The high interaction at moderate glass
contents along with a low interaction at high glass contents points to ASR as the likely
cause of the interaction, as will be discussed in the next section.
The intrinsic effect is substantial at all glass contents with coarse glass and increases
slightly with increasing glass content up to 90%. The intrinsic effect of fine-glass-only
aggregate (OOLFG) is much smaller, even becoming positive for one of the mixes, though
this may be due to other variables that were not included in the experimental design, and
the intrinsic effect for this mix is assumed to be 4% in the analysis and conclusions that
follow. This effect correlates with a change in the glass form and gradation; the relatively
good performance of the fine glass compared to the coarse glass aggregate is probably
because the dimensions of the interfacial microstructure ( 4 0 - 150 pm thick) are of the
same order of magnitude as the size of the glass aggregate particle itself, and so the
microstructure is able to bridge over the glass aggregate particle and incorporate it into its
structure. The coarse glass aggregate particles, on the other hand, are many times larger
than the thickness of the interfacial zone, and present a large, smooth, and flat interface
that can produce a definite plane of weakness.
DURABILITY
To the author's knowledge, freeze-thaw testing and exposure field trials have not been
previously researched with waste glass aggregate. Thus this work is useful in demonstrating
that the freeze-thaw durability of waste glass mixes is generally promising - it is able to
match the performance of low d c ratio control concrete with optimal proportions of glass
aggregate. Control mixes with no glass display slightly more stiffness degradation over 350
cycles of exposure than the OO/FG mixes. Weight loss results are somewhat less promising
but acceptable for the glass aggregate, with an average weight loss of ~ 2 % over 350 cycles,
compared to 51% for the control mixes.
Based on visual assessment, the field trial exposure test sections have little noticeable
degradation due to either abrasion or freeze-thaw exposure. Both the 20%/20% OO/FI glass
aggregate mix and the 0%/20% control mix used in the severely exposed drive-out section of
the sidew'ak are showing minimal signs of deterioration.
Durability under potential ASR attack will be discussed at length in its own section.
EFFECTS OF FLY ASH
Because fly ash will generally be necessary as part of a mix design with waste glass aggregate,
the effects of fly ash on the concrete mix must be taken into account, especially because the
Class F fly ashes, which are most effective in mitigating ASR, are also much more variable
than many of the higher grade Class C fly ashes.
Some of the Class F fly ashes commonly used in concrete production do not fall within the
ASTM guidelines limiting S03, free carbon, particle size distribution, and other critical
parameters, as has been detailed in Chapter 3 with regard to the fly ashes used in this
research. The observations made during this research suggest that consistent effects cannot
be assumed either between several suppliers of fly ash or between shipments of a single
supplier - parameters such as water demand or demand for air-entraining admixture can
vary by as much as a factor of two. Several researchers, however, including Cabrera, et al.
(1 986) have specifically studied variability in fly ash sources and have suggested more liberal - parameters than the ASTM guidelines as acceptable for use in concrete.
In combination with waste glass, many of the potential effects of glass aggregate are modified
or masked by the effects of fly ash, and the waste glass can even interact with and moddy the
behavior of the fly ash itself. Normally, fly ash has a consistent effect on strength
development, usually producing somewhat lower strengths initially, followed by higher long-
term strength. Because this pattern can be modified by the presence of glass, the effects of
fly ash, the effects of glass, and the effects of interactions between them have been separated
in Table 5.1, above and discussed more thoroughly in the next section.
BEHAVIOR DURING PROCESSING AND IN FRESH CONCRETE AND WATER DEMAND
As glass aggregate is received from a recycling plant, it will typically include contaminants:
paper, plastic, and other light components of the original form of the glass as packaging, as
well as sugar and other chemical or food contaminants. The effects of either removing these
by washing, or not, must be considered and its necessity must be clear before it is undertaken,
since the cost of washing waste glass aggregate may equal or exceed the cost of the raw glass
aggregate itself. Washing glass aggregate before use has an overwhelming effect on strength,
as shown in Table 5.2 where the strength without washing is indicated as a fraction of the
strength with washing.
TABLE 5.2. STRENGTHS rn WASHED VS. UNWASHED GLASS AGGREGATES.
(MPa) (MPa) Strength with Strength without Strength without
Washing Washing Washing
48%/20% CAIFA (28 days) 14.07 11.17 79%
24%/25% OOJFG (28 days) 3 1.08 18.27 59%
24%125% OOPG (56 days) 45.41 25.42 56%
The differences evident in this comparison include the effects of a slight change in gradation
of the glass aggregate due to the removal of some of the fine particles in the washing process
94
(compare gradations of glasses CA vs. CB, FA vs. FB, and FF vs. FG in Figures 3.1, 3.2 and
3.3, respectively). The effect of the gradation of the glass aggregate on strength will be
discussed below, but it is clear that the small change in gradation involved in the washing
procedure does not account for the majority of the change in strength, particularly since the
large difference in strength between washed and unwashed glass aggregate is not
accompanied by a significant difference in water demand, which is the primary direct effect of
a change in gradation.
Even after washing, however, the effects of glass aggregate on the properties of fresh
concrete are dramatic: a substantial decrease in slump and workability for a given water
content along with a somewhat reduced frnishability and some increased tendency toward
bleeding and segregation. AU of these effects are much more evident with coarse glass
aggregate or poorly graded fine glass aggregate, but there is some effect even with the
optimal fine glass aggregates. These effects on water demand and workability affect strength
as well, because the wlc ratio must be adjusted to keep workability within a usable range.
Any fine material used in concrete will exhibit a demand for water to wet the surface area of
the material and develop the electrostatic double layer necessary for it to move easily within
the fresh mix. Glass' characteristics in this regard and its interaction with fly ash will be
discussed below along with their combined interactions with air-entraining admixtures and
water reducers.
EFFECTS OF PARTICLE SHAPE AND TEXTURE
The most obvious fundamental causes of the various strength effects of glass aggregate are
the particle shape and the texture, which differ substantially between natural and glass
aggregates. The coarse glass retains the plate-like shape of the bottles from which it is
derived, with the finer gradations becoming more and more regular in their shape and losing
some of their sharpest and most angular edges. Glass aggregate that was crushed to less than
~ 1 . 5 rnm is generally quite regular (see Figure 1.1 through 1.6). This regular shape is not
assured by the simple fact of the glass having a fine gradation, however - the glass ground in
the laboratory, glasses FD and FE, exhibited a very flaky particle shape due to the method of
grinding used.
The particle shape along with the smooth texture of the glass aggregate pieces are certainly a
large part of the reason for the increased water demand and decreased workability of concrete
with glass aggregate. Poorly shaped aggregates are generally known to produce this type of
behavior, along with increased bleeding and segregation. The coarse glass pieces especially
produced observable anomalous behavior in the fresh concrete, with visible bleeding around
the glass particles and extremely poor cohesion with the cement paste. The flaky particles in
the lab-ground aggregates (glass FD and FE) were too small to observe similar behavior
visually, but their higher water demand suggests that the mechanisms involved were similar.
The flat particles with a smooth surface texture may develop a weaker interface due to the
collection of bleed water along the smooth and flat interface that allows a continuous layer of
relatively weak, well-oriented CH crystals to form. This tendency to collect bleed water at
interfaces is a common cause of poor strength among concretes with poorly graded
aggregates (Roberts 1989), and the smooth surface texture of the glass coarse aggregate may
simply aggravate this effect. This same property of coarse glass aggregate may prevent it
from developing the cohesive layer of fresh cement paste that normally allows coarse
aggregate particles to move easily within a mass of fresh concrete.
If a pozzolanic reaction then occurs, it may consume this layer of CH and redeposit it as a
stronger layer of CSH - an effect noted by Roberts (1989). If ASR occurs, on the other
hand, this layer may be incorporated into the more fluid ASR gel which does not contribute to
strength. This possibility is supported by SEM images of the concrete samples in this
research showing smooth, continuous gaps at many of the interfaces between coarse glass
aggregate and cement paste.
EFFECTS OF GLASS AGGREGATE GRADATION
It is clear that smaller, sub-angular particles are far superior to larger, flat and elongated
particles. It is difficult, however, to separate the effects of the particle shape from the effects
of gradation - there seems to be a substantial correlation between a finer particle size and a
more regular particle shape. Making comparisons between materials of similar fineness, i.e.
gravel vs. coarse glass, sand vs. fine glass, and fly ash vs. powdered glass, the coarse glass
produced substantially harsher workability than similarly graded gravel, the fine glass produced
approximately the same or slightly harsher workability than similar sand, and the powdered glass
produced slightly better workability than similarly graded fly ash. At the same time, there may be
physiochemical reasons for a smaller glass particle performing better than a larger one. If
glass aggregate has a distinctive effect on the development of the ionic double layer, this
effect may change as an aggregate particle becomes smaller and more regular and has fewer
distinctive, sharp edges.
The effects of glass form and gradation on ASR will be discussed below.
EFFECTS OF POWDERED GLASS
While waste glass in typical crushed sizes might replace sand as fine aggregate, powdered
glass has possible uses similar to those for Class F fly ashes. It has a similar chemical
composition, and its amorphous morphology is at least similar to the outer shell of most fly
ashes. It is possible that powdered glass will provide the same effects in concrete that Class F
fly ashes do, but current results are somewhat ambiguous, with apparent contradictions
between accelerated ASR results and strength results. It will be necessary to conduct further
research, including long-term concrete prism ASR testing to determine what effects
powdered glass has on ASR and whether it is usable for some of the same purposes as fly ash.
The effects of powdered glass on the properties of fresh concrete are generally positive and
encouraging. The demand for water increases only slightly when cement is supplemented
with small amounts of powdered glass (1% - 2.5%) and then decreases gradually for
supplements up to 20%. The demand for air-entraining admixture is likewise decreased
slightly. These effects are probably due to the very low free carbon content of powdered
glass compared to similarly graded Class F fly ashes.
The effects of powdered glass on strength, however, are ambiguous. Several of the test
mixes lost strength at some point during their development, though some of them resumed
normal strength growth eventually. The causes of this behavior are unclear; it is possible that
some ASR deterioration is taking place, but within the experimental design used in this
research, it was not possible to separate the conflicting effects of ASR and the interaction of
ASR with pozzolanic strength development from hydration and strength development.
The likely cause of the differences between Class F fly ash and powdered glass are the alkali
contents and the slightly different morphologies. The higher alkali content of the powdered
glass, combined with the completely amorphous structure of glass compared to an amorphous
layer surrounding a crystalline core for fly ash, and a somewhat finer gradation overall have
probably liberated a much higher concentration of alkalis than that liberated by the fly ash.
This, combined with the lower quantities of powdered glass used as a cement supplement
rather than a cement replacement, overwhelmed any ability of the powdered glass to mitigate
the ASR.
If powdered waste glass is used, the gradation and particle shape must be controlled to the
same extent as they would be for waste glass aggregate. It has been suggested that many of
the positive effects of fly ash, especially reduction of water demand, are largely attributable to
the spherical shape resulting from the formation of fly ash by precipitation in air, since
powdered waste glass is ground rather than being formed by precipitation, this alone might
significantly change its effect on concrete. Several researchers (Monzb, et al. 1995) have
examined this, however, and their results suggest that ground particles of a similar gradation
will have largely the same effects as fly ash formed by precipitation and only slightly higher
water demand.
EFFECTS OF INTERACTIONS BETWEEN MATERIALS
EFFECTS OF INTERACTION WITH GLASS ON BEHAVIOR OF FLY ASH
A substantial effect of glass aggregate on strength development by fly ash has been observed,
in some cases eliminating nearly all of the strength development expected from the fly ash
itself, thereby reducing the strength of the concrete by as much as 20% - 25% (see Table 5.1
and associated discussion). This effect is most noticeable in those mixes that have a near-
pessimum proportion of glass aggregate.
Figures 5.1 and 5.2 are presented to investigate this effect. Each of the strengths in Figures
5.1 and 5.2 has been normalized as the ratio of the strength of the given mix to the strength of
the equivalent mix with 0% fly ash at the same age (e.g., the normalized strength of 12%/35%
at 90 days is the ratio of the strength of 12%/35% at 90 days to the strength of 12%/0% at 90
days).
If glass were to have no effect on the pattern of strength development, but rather only on the
overall strength developed, all of the curves on one figure would coincide because the curve
would be a characteristic of the type and amount of fly ash and all of the curves on one figure
have the same type and amount of fly ash. If, on the other hand, glass has an effect on the
pattern of strength development, but with no interaction between glass and fly ash, then a l l of
the curves on each figure would end up at approximately the same level in the end because
the effect of the glass aggregate alone on the overall level of strength development is already
discounted by the normalization.
10 100 1000 Age (days)
FIGURE 5.1. DEVELOPMENT OF STRENGTH BY GLASS CONTENT - 20% FLY ASH.
Neither of the fore mentioned patterns are observed - rather, what is observed for 20% fly
ash (Figure 5.1) is that the curves for 24%, 36% and 48% glass nearly coincide, with the
curve for 12% glass somewhat below them and the 90% glass curve significantly above the
others, while the curve for 0% glass is far above the rest. Because the effects of glass
aggregate alone are already discounted, this may be taken as an indication of an interaction
between glass and fly ash - with the glass reducing the strength developed by the fly ash.
With 35% fly ash (Figure 5.2), the pattern changes, with 36% glass at the bottom, and the
12% 24% and 48% glass curves grouped together, in an overall order
36%<24%<48%<12%. The curve for 90% glass ends up far above the others, and the 0%
glass curve is again at the top. Noting that the effect of the glass alone is already discounted
by the normalization, it seems that the glass is again affecting the strength development by fly
ash, but does so to a lesser degree at 90% replacement than at lower replacement levels.
Moderate amounts of glass cause a large reduction in the strength development, while use of
90% glass aggregate reduces it only moderately, and allows greater strength development at
later ages relative to other glass contents. Several causes may be contributing to h s
behavior:
It appears that fly ash develops much of its ability to mitigate ASR by acting as a very fine
and reactive material that forms a low C:S CSH gel that is able to adsorb alkalis and
become a sort of alkali-silica gel without subsequently causing deleterious expansion -
thus simultaneously increasing the amount of ASR reactive material in the mix and
reducing the pessimum proportion of the total mix greatly. This pushes the total mix far
out onto the over-pessimum portion of the ASR pessimum curve, and thereby reduces the
ASR deterioration.
Other effects that work hand-in-hand with this is that as the alkali content of CSH gel
increases its viscosity also decreases (Jones 1988), and the alkali-gel that is generated is
distributed throughout the matrix among the fly ash particles rather than being
concentrated around reactive aggregate particles. These two effects together change the
ASR gel development from a few large pockets of viscous gel to many more small pockets
of less viscous gel, which is able to be absorbed by the concrete matrix.
The effect on strength, however, is that the gel thus developed by the fly ash is not able to
contribute strength to the concrete, and its production consumes fly ash which would
otherwise react to form structural CSH gel. The alkali ions incorporated into the CSH at
low C:S ratios may also expel ca2' ions from the gel (Qian, et. al. 1994), further
contributing to the loss in strength.
The fly ash is also unable to densify and improve the paste-aggregate bond as it might
otherwise do because the CSH developed with ASR migrates away from the paste-
aggregate interface after formation (Hudec and Banahene 1993). The result is actually a
weaker paste-aggregate bond because of the consumption of the CH crystals at the
interface which, though weak, did provide some strength, rather than a strengthening of
the interface as CH crystals are replaced by CSH. This effect may be compounded by
glass aggregate, especially coarse glass aggregate, because of the large, smooth, and flat
surface which encourages the growth of a large, continuous layer of CH at the interface.
This decrease in strength development is counter to the hypothesis by some researchers
that fly ash mitigates ASR by strengthening the concrete matrix, though the low-viscosity
gel may still densify the matrix and reduce the permeability.
The same interaction is also visible in Figure 5.3, where strength is presented at an age of 180
days and k normalized only according to wl(c +A, rather than glass content, so the effect of
the glass aggregate itself is still present. The important observation is that the fitted lines for
0% glass with fly ash F1 and F2 are similar and positive; while the lines for 12% through 48%
glass are negative, indicating a loss of strength with increasing fly ash content - suggesting
that the fly ash is not contributing as much, if at all, to strength with these glass contents.
20%/y% Fine GIs, FA 1 F2
4 24%/y% Fine GIs, FA F2 Phase-I1 CEIFC, FA F1
0% 10% 20% 30% 90%ly%, CCIFA. FA FI Fly Ash Content (% of Cementitious)
FIGURE 5.3. RELATION OF STRENGTH TO FLY ASH CONTENT - MODERATE ALKALI MIXES.
INTERACTIONS WITH AIR-ENTRAINING ADMIXTURE AND W A ~ REDUCER
The amount of air-entraining admixture required is related to the type and content of glass
aggregate in Figure 5.4, to the type and content of fly ash in Figure 5.5, and to powdered
glass content in Figure 5.6. The water demand of mixes with high-range water reducer
(HRWR) is related to glass content in Figure 5.7 with several fly ash contents noted on the
figure.
103
Comparing Figures 5.4 and 5.5, glass aggregate is seen to have only a small effect on the air-
entraining admixture required - most of the demand is clearly deriving from the fly ash. The
upward trend with increasing glass content that is apparent in Figure 5.4 is actually an effect
of fly ash rather than glass, and is a result of the higher glass contents generally being
accompanied by higher fly ash contents as well. This may be seen by comparing, for example,
the control mix with no glass and 25% fly ash (265 mum3/1% Air) to similar mixtures with
24% glass (likewise at 260 to 270 m ~ m ~ / l % Air).
5 0
0% 12% 24% 36% Glass Content (% of Total.Aggregate)
FIGURE 5.4. AIR-ENTRAINWG ADMIXTURE REQUIRED BY TYPE AND CONTENT OF GLASS AGGREGATE.
It is clear from Figure 5.5 that both the type and content of fly ash have substantial effects on
the admixture requirements, with typical increases from 1 to 2.5 times for 0% to 15% fly ash,
ranging linearly up to 2.5 to 6 times the air-entraining admixture required for control concrete
at 35% fly ash replacement.
0% 5% 10% 15% 20% 25 % 30% Fly Ash Content (% of Total Cementitious)
FIGURE 5.5. AIR-ENTRAINING ADMIXTURE REQUIRED BY TYPE AND CONTENT OF FLY ASH.
0% 5% 10% 15% 20% Powdered Glass Content (% of Cement)
FIGURE 5.6. AIR-EI~IR~ING ADMIXTURE REQUIRED BY CONTENT OF POWDERED GLASS.
<I
I - 20% Glass Aggr
o No Glass
-
b
0
I
Figure 5.6 shows the air-entraining admixture required by various amounts of powdered glass
as a cement supplement. There is a slight beneficial effect at all levels of addition less than
20%. Because the powdered glass has an extremely low free carbon content, it is able to
lubricate the mix and reduce the need for air-entraining admixture to act as a particle
surfactant and allowing it to stabilize air bubbles instead, thus limiting demand - in contrast
to the fly ashes used, which have such a large demand due to their own free carbon content
that any reducing effect due to workability enhancement is negligible.
Similar effects are noted when comparing the effects of HRWR on the various mixes
(Figure 5.7). For mixes with no glass and no fly ash, there is a large effect of adding HRWR,
while for mixes with either glass or fly ash, or both, there is only a small effect at the dosages
of HRWR used. This effect does not necessarily cause an insurmountable problem for the use
of either glass aggregate or fly ash - it may simply limit the range of usable wlc ratios at a
given HRWR dosage. These mixes may require greater dosages of HRWR for significant
effects to be observed.
12% 24% Glass Content
FIGURE 5.7. WATER DEMAND WITH AND WITHOUT HRWR BY GLASS CONTENT.
L~LKALI-SILICA REACTIVITY AND MITIGATION
R E A ~ ~
Waste glass is clearly highly alkali-silica reactive. When used with moderate-alkali cement
and no fly ash or other measures to mitigate the reaction, certain combinations of glass
exceed allowable expansion criteria as early as 28 days after mixing.
The mechanisms of ASR expansion and deterioration are complex and not known with
certainty. The expansion observed in a particular case is determined by the total potential for
ASR expansion as determined by the amounts of the various reactants present, the rate of the
alkali-silica reaction and gel production, and the amount of gel expansion that is able to be
accommodated by the concrete matrix within a given time period - probably influenced by
the viscosity or other properties of the gel.
PESSIMUM BEHAVIOR
One of the defining characteristics of ASR, and one which many other researchers have also
observed, is what has become known as 'pessimum' behavior. Pessimum behavior is a
phenomenon wherein the greatest expansion and the greatest deterioration due to ASR are
observed not at the highest levels of replacement of natural aggregate by glass, but rather at
some moderate level. Either above or below this pessimum level, the expansion and
deterioration are less than at the pessimum level. Possible mechanisms whereby the
pessimum phenomenon is expected to occur are summarized in Chapter 2.
Pessimum behavior was observed for the glass aggregate studied in this research, and several
noteworthy conclusions may be drawn from the results:
This study showed that the pessimum proportion of glass aggregate is not an unchanging
parameter unlike the results obtained by previous researchers. A finer glass gradation
reduces the pessimum proportion, and with the addition of fly ash and with age the
pessimum level remains approximately constant and the peak moves to a slightly higher
glass content.
The concrete prism tests with fine glass aggregate displayed pessimum behavior at ~ 2 5 %
replacement of natural aggregate by glass, while in the accelerated tests, the pessimum
amount was ~ 5 0 % . This may indicate that ASR with fine glass depends on the mortar
fraction of the mix, while the coarse aggregate is relatively insignificant.
It might be noted that these observations of pessimum behavior's relation to surface area and
thereby to particle size may be limited to glass aggregates. Figg (1981) has observed that
ASR is primarily a surface phenomenon for Pyrex glass aggregate, while for Beltane Opal it
takes place throughout the volume of the aggregate and is independent of particle size. This
is likely because opal is reactive because it is cryptocristalline, i.e. has a crystalline or semi-
crystalline structure, but with micropores in the structure which allow reactive species to
penetrate, while glass is reactive because it is amorphous, i.e., all of its silica structures are
weakly held, but there are no openings which particularly allow access to the particle interior
(Gillott and Beddoes 198 1).
EFFECTS OF FLY ASH ON ASR
In examining the expansion of ASR concrete prisms, a pattern emerges when comparing
mixes with various fly ash contents (Figure 5.8):
First, the lowest expansion is generally not found with the highest fly ash content, rather a
minimum expansion is observed at some lower fly ash content and the expansion rises
slightly as the fly ash content is increased beyond that for a minimum expansion.
Second, the amount of fly ash required for minimum expansion increases with increasing
glass content - at 0% glass, 20% fly ash provides the minimum expansion; at 12% glass,
20% fly ash; at 48% glass, 25% fly ash; and at 90% glass, 30% fly ash provides the
minimum expansion. The 0% glass series trend is not entirely clear, possibly because of
the very slightly amount of reactive aggregate present, but the others show this effect very
clearly.
Note that this is not the pessimum effect, which is a phenomenon wherein a variation in glass
content produces a maximum expansion at some intermediate glass content. Rather, this is a
minimum expansion at an intermediate (rather than a maximum)fly ash content.
0% 5% 10% 15% 20% 25% 30% 35 % Fly Ash Content (% of total cementitious)
In Figure 5.8, the moderate-alkali coarse glass series are shown to allow analysis at 1095
days, an age which the low-alkali mixes have not yet reached.
-Mod, O%/y%, FA F1
-9 - Mod, 12%/y%, CAEA, FA F1
- - + . - Mod, 48%/y%. CCIFA, FA F1
- -* - Mod, 90%/y%. CAIFA, FA F1
Figure 4.33 suggests that the ability of fly ash to mitigate ASR also varies with the amount of
glass present. At high glass contents (90% glass aggregate), glass is not as reactive, because
- 0 - . - _ . .... -.)' - Mod-Alk Criterion
. . -. I I ..................:..-........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....................... r. ........................................ L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................................................................. "
.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.............................. ':: .................................... \ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . --. I& .....................................................................................................
...................................................................................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . - . . - _ .__
it is beyond the pessirnum proportion of glass; but it is also evident that fly ash is not able to
-
'*.---.-.-. .:
-._ .-.-.__ .......................-..,,.............
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .............................................................. .............................................................. ............................................................. .............................................................. .............................................................
-.-. -.---
109
limit reactions over the long term at these glass contents either. Note (Figure 4.33) that by
1095 days, all of the 90% glass mixes have exceeded the allowable expansion criterion,
though the mixes at the pessimum glass content with adequate fly ash for mitigation are still
below or only slightly above the criterion.
M~IGATION
Besides using fly ash, several other possible mitigation schemes have been used in practice or
in research in the past, and are reflected by some of the experimental mixes in this research:
judicious proportion of natural and glass aggregate, using low-alkali cement, air-entrainment,
use of LiOH or other alkali salts as admixtures, and using powdered glass in place of fly ash.
The results of using powdered glass are inconclusive - it may prove effective with further
experimentation with a wider range of glass aggregate-powdered glass combinations, while
the use of LiOH is beyond the scope of this research. Judicious aggregate proportioning, use
of low-alkali cement, and air-entrainment show promise as partial solutions to ASR in this
research, but cannot be relied upon to consistently provide complete mitigation. Fly ash is the
only mitigation measure which may be unequivocally recommended based on the results of
this research; particularly in the more variable mixing and exposure environments of field
concrete, other measures provide insufficient assurance of mitigation.
OFTEibU PROPORTIONS OF WASTE GLASS AGGREGATE AND FLY ASH
In light of the pessimum behavior of glass with regard to both ASR expansion and strength,
this behavior must be taken into account when selecting aggregate proportions. As a finer
gradation is used, the pessimum proportion drops; e.g. for a CA/FA mixture with an average
glass particle size of 3 - 4 rnm, the pessimum proportion is about 36%, while fine glass
mixtures with average glass particle sizes of 0.5 - 1.0 mm have pessimum proportions around
24%.
Optimizing the glass gradations and proportions would thus require meeting the following:
A fine, well graded waste glass aggregate, such as Glass FG used in this study to replace
the natural sand in the concrete mix design.
A proportion of glass aggregate somewhat below the pessimum proportion for that
gradation - using a slightly coarser but still acceptable glass gradation will allow use of
more glass aggregate with acceptable long-term performance. For the glasses FG and FI
used in this research, a 15% to 20% replacement of aggregate with glass would be
required.
Fly ash of appropriate gradation and quantity used to mitigate ASR.
For the cement-fly ash-aggregate combinations studied, the optimum proportion of fly ash is
~ 2 0 % of the total cementitious material, though the results suggest that high quality fly ash
with optimum glass aggregate may be effective at somewhat lower levels, possibly ~ 1 0 % .
Higher than optimum proportions of fly ash produce somewhat higher expansion because of
the ASR reactivity of the fly ash itself. Aggregates, cements and other admixtures should be
selected with the goal of minimizing the amount of fly ash necessary for ASR mitigation,
because the fly ash used to mitigate ASR will demand water while adding little to the strength
of the concrete.
USE OF WASTE GLASS AGGREGA'IE
Waste glass aggregate will generally be obtained from commercial municipal recyclers, and
the condition and physical properties of the glass must be controlled to produce acceptable
concrete.
The particle shape must approach that of a nearly cubic, or at least regular, sub-angular
sand, rather than flakes or plates. Laboratory experience demonstrated that either of these
particle shapes can be produced during glass processing, depending on the crushing
method used.
The glass must be clean. Food or chemical contaminants, especially sugars, have been
shown to have an overwhelming effect on strength (up to a 40% loss of strength at 28
days) in the quantities typically found on unwashed municipal waste glass. Other
contaminants, such as paper or plastic remnants, also have an effect, though they are not as
severe and have not been quantified.
The glass must be well-graded and must be provided within a consistent gradation. Some
crushing and processing methods produce severely uniformly graded aggregate. This
problem may be exacerbated by the washing process if care is not taken to avoid loss of
fine material.
The strength of the glass aggregate and the composition of the glass are probably also
significant, though the effects of these parameters on the mix was not included in the scope
of this research.
It will generally be necessary to use water reducers to counter the water demand of even
optimal glass aggregate. The segregation and bleeding what have been observed as minor,
controllable problems with glass aggregate may be compounded if water reducers are not
used judiciously or if an otherwise unacceptable waste glass aggregate is used with excessive
quantities of water reducers.
USE OF MINERAL ADMIXTURES IN WASTE GLASS AGGREGATE
Optimizing the type of fly ash is outside of the primary scope of this research and will
generally require some trial in any case, but several points may be noted:
The alkali content of the fly ash should be kept as low as possible. The interaction of fly
ash gradation, fly ash alkali content, and glass aggregate reactivity in determining the
extent and rate of ASR deterioration was not addressed directly within the scope of this
research, but the results from trials with powdered waste glass and the experiences of
other researchers (BCrub6, et. al. 1995b, among many others) suggests that about 5%
available alkali content in the fly ash is a reasonable limit, with fly ashes near 5% being
accepted only after trials.
The effects of fly ash on air-entraining and water reducer admixture requirements are
exacerbated by the presence of glass aggregate, therefore, the free carbon content of fly
ash used with waste glass aggregate should be kept to a minimum, to reduce the additional
admixture demand.
The gradation of the fly ash may affect the ability of the fly ash to mitigate ASR, as has
been discussed above. Current results suggest that a fly ash with a moderate rather than a
very fine gradation may be better, provided that the of larger particles does not
drive up the available alkal~ and free carbon contents. A moderate gradation may provide
longer-lasting mitigation of ASR than a fine-gradation fly ash.
The SiOz, and possibly the CaO and MgO contents of the fly ash or powdered glass will be
factors in their effectiveness in the mitigation of ASR (Kobayashi, et al. 1989), but these
effects are beyond the scope of this research.
ASR TEST PROCEDURES
While the accelerated mortar bar test (ASTM C1260) is gaining acceptance within the
concrete industry, and is probably the best available screening test, its usability for the
fundamental study of ASR is limited. Several factors suggest that the unaccelerated concrete
prism test is still necessary at least as a supplement to ASTM C1260 when results beyond a
screening evaluation are required.
The difference in the pessirnum proportion in the concrete prism tests (pessirnum at 36% -
48% with coarse and fine glass vs. 20% - 24% with fine glass) also suggests that ASR might
best be regarded as a phenomenon of the mortar fraction of the mix. If the reactive aggregate
is present in the coarse aggregate fraction of the concrete, the gradation must be changed
before it can be used in the mortar bar test and any interpretation of the results beyond a
screening evaluation must be made very cautiously.
Particularly important is a consistent equivalence between aggregate proportions in the
mortar bar and aggregate proportions in the corresponding concrete. If the reactive
aggregate is in the fine aggregate fraction of the concrete, making the mortar bar equivalent
to the mortar fraction of the concrete (including the reactive aggregate) gives results
consistent with concrete prism tests. For example, a concrete mix with 60% coarse natural
aggregate, 20% fine natural aggregate and 20% fine glass aggregate would be best
represented by a mortar bar with 50% fine natural aggregate and 50% fine glass aggregate.
AREAS REQUIRING FURTHER RESEARCH
As this research was completed and the data analysis proceeded, several areas were
identifiable as potential future research areas:
Only one dosage of high-range water reducer (HRWR) was used, selected according to the
manufacturer's instructions before the I-IRWR series began. Because glass and fly ash,
especially in combination, displayed much smaller response to HRWR than the control
mixes, a larger dosage may be appropriate and might be useable without the air-
entrainment destabilization which is characteristic of a HRWR overdose.
114
The Powdered Glass Series was conceived as parallel to similar mixes with silica fume,
with powdered glass supplementing rather than replacing cement and used in fairly small
quantities (1% - 20% cement supplement). The powdered glass might be better modeled
as similar to Class F fly ash. According to this model, the powdered glass series could be
repeated with powdered glass used as a cement replacement in proportions from 10% -
40%. As powdered glass might be a useful outlet for waste glass recycling in and of itself,
experimental trials might be made both with and without waste glass aggregate included as
part of the mix.
A more thorough understanding of the interaction between glass and fly ash might be
developed by a direct approach to an understanding of ASR mechanisms (rather than only
observing symptoms). SEM and optical microscopy and chemical characterization of glass
and of concrete pore solutions would be ideal components of such a program.
CHAPTER 6 - SUMMARY, CONCLUSIONS AND
RECOMMENDATIONS FOR APPLICATION
An experimental research program was conducted to: (1) identlfy characteristics of waste glass
that produce satisfactory concrete for pavement applications, (2) to document the alkali-silica
reactivity of waste glass aggregate and determine means of mitigating this ASR, and (3) to
determine the effects of waste glass aggregate and powdered waste glass on the strength and
durability of concrete. The performance of glasdfly ash concrete was evaluated, and experimental
work conducted by the author, results of others at the University of Wisconsin, and other
researchers' published results were used to synthesize conclusions about the processes and
mechanisms of ASR and strength development in glasdfly ash concrete. Evaluation of the
experimental mixes included consideration of compressive strength, fieezelthaw resistance, and
resistance to ASR deterioration at ages firom one month to three years. Some study of the
interactions between the experimental materials and air-entraining admixtures, water-reducing
admixtures, fly ash and fine powdered waste glass was included to aid application of the
conclusions to pavement trials.
STRENGTH
Strength has been used in this research as the primary measure of the effects of glass
aggregate on concrete. The range of strengths observed were very broad - at 180 to 365
days ranging from less than 10 MPa up to greater than 50 MPa. The effects of glass
aggregate on strength have been be divided into three catagories:
1 . Glass aggregate displays a water demand for workability greater than that of natural
aggregate. Satisfaction of this water demand increases the wlc ratio of the concrete,
thereby resulting in a lower strength. This effect increases steadily with increasing glass
content, with the fine glass mixes exhibiting slightly lower demand than the coarse glass
mixes.
2. Glass aggregate reduces the strength developed by fly ash in the cementlfly ash mix in
situations in which ASR is active, reducing the strength of concrete mixes made from
typical proportions of glass and fly ash by as much as 25%. This effect is substantial for
all of the mixes with moderate-alkali cement, while for the mixes that include low-alkali
cement the magnitude of this effect is much lower. The results obtained with various
g l a ~ contents points to ASR as the likely cause of the interaction. In the high-alkali
ASR environment, the low C:S ratio gel formed by fly ash becomes an alkali-CSH gel of
low viscosity. Thus rather than form structural CSH gel, fly ash may form a fluid alkali-
CSH gel that moves away from the aggregate particles and is unable to densify and
improve the paste-aggregate bond, leaving instead a weaker interface devoid of both CH
crystals and CSH gel.
3. Finally, there is a strength loss intrinsic to the glass aggregate, i.e., it cannot be accounted
for by either a change in wlc ratio or air content, or a change in the behavior of the
cementitious components of the mix. This effect is probably due to a difference in paste-
aggregate bond for a glass particle vs. a natural aggregate particle, and can amount to
anything from a 25% strength loss to a 5% strength gain. The relatively good
performance of fine glass compared to coarse glass aggregate is probabIy because the
dimensions of the interfacial microstructure (-50 - 150 pm thick) are of the same order
of magnitude as the size of the glass aggregate particle itself, and so the microstructure is
able to bridge over the fine glass aggregate particle and incorporate it into its structure.
The coarse glass aggregate particles, on the other hand, are many times larger than the
thickness of the interfacial zone and present a large, smooth, and flat interface which can
produce a definite plane of weakness. This effect primarily reflects a change in the glass
form and gradation.
The contribution of each of these effect for several representative mixes was presented in.
Table 5.1, and is illustrated graphically in Figure 6.1.
ater Demand, CNFA & C E R 10%
Water Demand, OO/FG 5, 0% 5 A Intrinsic Effect, CNFA b - 10% CA
A Intrinsic Effect, OOFG -20%
U o Interaction, Mod-Alk Cement
-30% W 0 Interaction, Low-Alk Cement 2 -40% 9) T o t a l Effect, CNFA & Mod-Alk 3 -50% U . H + Total Effect, Low-Alk, CEJFC 6 4 0 % (d
-70% Interaction, Mod-Alk Cement
-80%
90 10% 30% 50% 70% Glass Content (% of Total Aggr.)
- - - - Water Demand, CAIFA & CE/FC
- - - Intrinsic Effect, CAEA & CEFC
Figure 6.1 illustrates the dramatic loss in strength due to the three combined effects in a mix
with indescriminate use of coarse glass and moderate-alkali cement - a loss in strength
ranging from 50% with 12% glass up to 80% with 90% glass. Also illustrated in Figure 6.1,
however, are the gains which can be realized by judicious selection of materials and
proportions:
By limiting the glass aggregate to a limited fine gradation and a more regular particle shape
(glass OO/FG) at a glass content of 20% - 24% of the total aggregate, the loss due to water
demand may be reduced from =lo% (with glasses CAEA and CEIFC) to about 0% - 5%,
and the loss due to the intrinsic effect may likewise be reduced from =30% (with glass
C M A ) to about 0% - 5%.
By using low-alkali rather than moderate-alkali cement as well, the loss due to the
interaction between glass and fly ash may be reduced from ~ 2 0 % to -5%.
The total effect of these design improvements is to reduce strength loss from ~ 6 0 % at a glass
content of 20% - 24% to a loss of about 0% to 15%.
DURABILITY
The freeze-thaw durability of concrete with glass aggregate is promising. With optimal
proportions of glass aggregate it is possible to match the performance of low wlc ratio control
concrete in accelerated freeze-thaw testing. Mixes with optimal glass aggregate (the OOIFG
mixes in the laboratory and the OO/FI mixes in the field) performed as well as or slightly better
than the control mixes, while the field trial exposure tests sections had little noticeable
degradation due to either abrasion or freeze-thaw exposure.
119
ASR REACTIVITY
Waste glass is clearly highly alkali-silica reactive. When used with moderate-alkali cement
and no fly ash or other measures to mitigate the reaction, certain combinations of glass
exceed allowable expansion criteria as early as 28 days after mixing.
Observations that the pessimum content varies with glass gradation (pessimum at 36% - 48%
of total aggregate with coarse glass vs. 20% - 24% of total aggregate with fine glass vs. 50%
of fine aggregate in the mortar bar test) suggest that ASR depends on the mortar fraction
with regard to critical proportions of glass and fly ash.
EFFECTS OF POWDERED GLASS
When waste glass is powdered very finely, its has potential for use as a mineral admixture. In
this research, powdered glass was used in a manner analogous to silica fume, i.e. as a cement
supplement at low (1% - 20%) addition levels; but based on the subsequently observed
behavior it appears that powdered glass might be better modeled as similar to Class F fly ash,
i.e. as a cement replacement at levels of 10% - 40% of the total cementitious materials, either
with or without waste glass aggregate. The strength results are ambiguous, possibly because
ASR deterioration took place beyond the ability of the powdered glass to mitigate. Powdered
glass as a cement supplement has only slight effects on water demand and air-entraining
admixture requirements.
EFFECTS OF FLY ASH
The effectiveness of fly ash in mitigation of ASR depends on the amount of reactive glass
aggregate in the mix. At proportions of 12% - 48% glass aggregate it was found that some
proportion of fly ash reliably mitigates ASR. For 90% glass aggregate no amount of fly ash
535% replacement of cement was able to mitigate ASR.
It appears that fly ash mitigates ASR primarily by acting as a very fine and reactive material
itself which consumes alkalis in the production of an ASR-like alkali-CSH gel. It causes a
simultaneous reduction of the pessimum proportion of the total mix and an effective increase
in the amount of ASR reactive material to far beyond the pessimum proportion. This,
combined with a decrease in the viscosity of CSH gel with increasing alkali content (Jones
1988) and a distribution of the reaction more evenly among the fly ash particles throughout
the concrete matrix, changes ASR gel development from a few large pockets of viscous gel to
many more small pockets of fluid gel, which is able to be absorbed by the concrete matrix.
For mixes which are problematic but are already beyond the pessimum proportion, fly ash
does not have much of an effect other than possibly to delay ASR slightly.
RECOMMENDATIONS FOR APPLICAT~ON
Waste glass aggregate can be used successfully in place of natural fine aggregate at
replacement levels up to 50% of the fine aggregate fraction. A glass gradation between 75
pm and ~ 1 . 5 rnm was found to produce strengths sirmlar to control concrete at comparable
W/(C +fi ratios. However, the initial strength gain is less than that of the control specimens
(an optimal mix with glass aggregate starts with only 75% of the strength of the control mix
at 7 days age). At 28 days the strength rises to ~ 8 5 % of the strength of the control, to ~ 9 5 %
at 180 days, and to ~ 1 0 0 % of the strength of the control at 365 days. Glass coarser than
about 1.5 mm produces poor strength when used as aggregate, due to its extremely poor
shape, poor surface characteristics, and high friability.
To design an effective mix with glass aggregate, in terms of strength and ASR mitigation, a
proportion of glass aggregate slightly less than the pessimum proportion seems optimal. This
proportion maximizes the use of glass while remaining within the range of glass contents in
which fly ash can effectively mitigate ASR. Fly ash should be used in proportions of =lo% to
20% of the total cementitious material.
In addition, the following characteristics will be required: the particle shape must approach
that of regular, sub-angular sand, rather than flakes or plates. Special care is required in the
crushing of glass aggregate to satisfy this. The glass must be clean, free of food or chemical
contaminants, especially sugars. The glass must be well graded, which will require some care
in the crushing and washing operations.
It will generally be necessary to use water reducers with glass aggregate to reduce the water
demand for workability. Care must be taken that the quantity of water reducer is tailored to
the glass aggregate mix. Glass aggregate is likely to demand greater quantities of water
reducer, while at the same time overuse might aggravate glass' slight tendency toward
bleeding and segregation.
Use of fly ash was the only procedure found to be consistently effective in mitigation of ASR.
Other procedures, in particular judicious aggregate proportioning, use of low-alkali cement
and use of air-entrainment, were found to be only partially effective. Low-alkali cement and
air-entrainment should still be used whenever possible in the design of a mix with glass
aggregate, however, because they reduce the degree to which fly ash must act to mitigate
ASR and thereby allow fly ash to develop a greater portion of its potential strength.
The fly ash used should be selected to have a high pozzolanic and low CaO content (generally
Class F) and the lowest alkali level possible. A 5% available alkali content is a reasonable
limit, however, an ash with an alkali content near 5% should definitely be evaluated in test
trials before use. The free carbon content should also be kept as low as possible to minimize
interaction with water reducers and air-entraining admixtures.
Both strength and freeze-thaw durability of glass aggregate concrete are comparable to
control concrete and well within the acceptable range for use in pavement. Both the
20%/20% OOIFG mix and the very similar OOFI mix showed excellent strength and durability.
The Field Trial test sections, at an age of =18 months, show performance of parallel
laboratory cylinders, strength cores, visual inspection and other testing of the sections
themselves similar to the performance outlined above for the laboratory series. These or
similar mixes should perform well in further pavement applications.
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Gaudette, S. P. (1993). "Pilot Study on the Effects of Waste Glass Aggregate on Portland Cement Concrete." An Independent Study Report prepared in partial fulfillment of the Master of Science Degree, Department of Civil and Environmental Engineering, University of Wisconsin-Madison.
Gillott, J. E. and Beddoes, R. J. (1981). "Continuing Studies of Alkali-Aggregate Reactions in Concrete." Proceedings of the Conference on Alkli-Aggregate Reaction in Concrete, National Building Research Institute, Cape Town.
Gillott, J. E. and Wang, H. (1 993). "Improved Control of Alkali-Silica Reaction by Combined Use of Admixtures." Cement and Concrete Research, 23(4), 973-980.
Goldman, A. and Bentur, A. (1993). 'The Influence of Microfillers on Enhancement of Concrete Strength." Cement and Concrete Research, 23(4), 962-972.
Gopalan, M. K. (1993). 'Nucleation and Pozzolanic Factors in Strength Development of Class F Fly Ash Concrete." ACI Materials Journal, 90(2), 117-121.
Hobbs, D. W. (1988). Alkli-Silica Reaction in Concrete, Thomas Telford, London.
Hobbs, D. W. (1986a). "Deleterious Expansion of Concrete Due to Alkali-Silica Reaction: Lnnuence of PFA and Slag." Magazine of Concrete Research, 38(137), 191-205.
Holnam (1993). "Laboratory Report." Mason City Plant, Mason City, Iowa.
Hudec, P. P. and Banahene, N. K (1993). "Chemical Treatments and Additives for Controlling Alkali Reactivity." Cement and Concrete Composites, 15,21-26.
Johnston, C. D. (1974). "Waste Glass as Coarse Aggregate for Concrete." Journal of Testing and Evaluution, 2(5), 344-350.
Jones, T. N. (1988). "New Interpretation of Alkali-Silica Reaction and Expansion Mechanisms in Concrete." Chemistry and Industry, (2), 40-44.
Kawamura, M. and Takernoto, K. (1988). "Correlation between Pore Solution Composition and Alkali-Silica Expansion of Mortars Containing Various Fly Ashes and Blast Furnace Slags." International Journal of Composites and Lightweight Concrete, 10(4), 2 15-223.
Khedr, S. A. and Abou-Zeid, M. N. (1994). "Characteristics of Silica Fume Concrete." Journal of Materials in Civil Engineering, 6(3), 357-375.
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Kosrnatka, S. H. and Panarese, W. C. (1988). Design and Control of Concrete Mixtures, 13th Edition, Portland Cement Association.
Lafarge Corporation (1991). "Cement Mill Test Report." Alpena Plant, Southfield, Michigan.
Lane, D. S. (1991). "Alkali-Silica Reactivity: An Overview of a Concrete Durability Problem".
Lenzner, D. (1981). "Influence of the Amount of Mixing Water on the Alkali-Silica Reaction." Conference on Alkali-Aggregate Reaction in Concrete, National Building Research Institute, Cape Town.
Ludwig, U. (1981). 'Theoretical and Practical Research on the Alkali-Silica Reaction." Proceedigs of the Conference on Alkali-Aggregate Reaction in Concrete, National Building Research Institute, Cape Town.
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128
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TABLE A3.1.1. CEMENT AND POWDERED GLASS CHARACTERISTICS.
LOW-~lkali' ~od-Mkali2 Class c3 Cement Cement Fly Ash
96 by Weight
SiOz 20.6
N 2 0 3 4.7
Fe203 2.7
so3 2.7
CaO 62.8
MgO 2.2
Moisture Content 0.10
Loss on Ignition 0.90
Na2O --
K20 --
Total Alk. as.Na20 0.50
Specific Gravity 3.15 3.15 2.43
1 Holnam Cement Corp. (1993)
LaFarge Corp. (1991)
Warzyn (1991a)
~ ~ ~ i c a l ~ powdered5 class F~ Class F~ Class F' Silica Fume Glass Fly Ash F1 Fly Ash F2 Fly Ash F3
-- Chmid Compmitiaa % h_u W e a t
SiO2 = 92 = 67 37.02 39.44 31.42
Fez03
CaO
so3
p205 -- -- 0.37 0.33 0.28
Moisture Content = 0.0 0.05 0.05 0.10 0.10
Loss on Ignition = 1.6 -- 0.20 3.79 15.18
Na20 = 0.4 = 15 4.37 2.43 1.48
K20 = 0.7 = 1.4 1.19 1.36 1.33
Total Alkalis as Na20 = 16 5.15 3.32 2.36
Specific Gravity = 2.35 2.15 2.72 2.64 2.30
ACI Committee 226 (1987a)
Typical composition of container glass from Figg (198 1)
W & L (1991)
' W & L (1994)
WEPCO (1994)
0.001 0.01 Particle Size (mm)
FIGURE A3.1.1. GRADATIONS OF CEMENTS, FLY ASHES, POWDERED GLASS AND SILICA FUME.
APPENDIX 3.2
VAFUABLE PARAMETERS OF THE CONCRETE MIXES
TABLE A3.2.1. VARIABLE PARAMETERS OF THE GLASS-FLY ASH SERIES. - - - - -
Batch(s) Fine Glass Coarse Glass Fly Ash Type I Cement WR Air Type I % of Type I % of % of Total Type Type Entmd. Total Aggr Total Aggr ( C +J)
None
None
FBI 1 0%
FA/10%
FA/10%
None
None
None
None
FA/4%
FA/4%
FA/8%
FA/4%
None
CA/48%
None
CBl38%
CA/38%
CA/38%
None
None
None
None
CA/8%
CN8%
CA/16%
CA/8%
None
F 1120%
None
F1120%
F 1120%
Cl20%
F 1120%
F1125%
F 1130%
F1/35%
None
F 1120%
None
F1125%
None
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
None
None
None
None
None
None
None
None
None
None
None
None
None
None
TABLE A3.2.1. VARIABLE PARAMETERS OF THE GLASS-FLY ASH SERIES (CONTINUED)
Batch(s) Fine Glass Coarse Glass Fly Ash Type I Cement WR Air Type 1 % of Type I % of % of Total Type Type Entmd. Total Aggr Total Aggr ( C +f)
F1/30%
None
None
F1/35%
F1/20%
F1/25%
F 1120%
F1/30%
F1/35%
F1/25%
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
None
None
None
None
None
None
None
None
None
None
86, 87, FA/13% CA/23% F1/30% Mod None No 88,89
90, 91, FA/13% CA/23% F1/35% Mod None No 92,93
94,95, FA/10% CC/38% F 1120% Mod None No 96,97
98,99, FA/lO% CC/38% F1/25% Mod None No 100,101
TABLE A3.2.1. VARIABLE PARAMETERS OF THE GLASS-FLY ASH SERIES. (CONTINUED)
Batch(s) Fine Glass Coarse Glass Fly Ash Type / Cement WR Air Type / % of Type / % of % of Total Type Type Entrnd. Total Aggr Total Aggr (C +f)
102, 103, FA/10% CC/38% F1/30% Mod None No 104,105
106, 107, FA/10% CC/38% None Mod None No 108, 109
110, 111, FA/lO% CC/3 8% F1/35% Mod None No 112, 113
114, 115, FA/18% CC/72% None Mod None No 116, 117
118, 119, FA/18% CC/72% F1/20% Mod None No 120,121
122, 123, FA/18% CC/72% F1/25% Mod None No 124, 125
126, 127, FA/18% CC/72% F1/30% Mod None No 128, 129
130, 131, FA/18% CD/72% F1/35% Mod None No 132, 133
134, 135, FC/8 % CE/16% C/25% Mod None No 136
137, 138, None None None Mod None No 139
140, 141, None None None Low None Yes 142
143, 144, FC/4% CE/8% F 1120% Low None Yes 145
146, 147, FC/8% CE/16% F1/25% Low None Yes 148
149, 150, FC/8% CE/ 16% F1/30% Low None Yes 15 1
TABLE A3.2.1. VARAIBLE PARAMETERS OF THE GLASS-FLY ASH SERIES. (CONTINUED)
Batch(s) Fine Glass Coarse Glass Fly Ash Type Cement WR Air Type/ % of . Type/ % of / % of Total Type Type Entrnd. Total Aggr Total Aggr (C +fi
Low None Yes
Low None Yes
Yes Low High
None
None
Low High
Low High
Yes
Yes
FF/24%
~ ~ 1 2 4 %
None
FG/20%
None
None
None
None
Low High
Low High
Low None
Low High
Yes
Yes
Yes
Yes
None Low Med Yes
None Low High Yes
None None None Low High Yes
TABLE A3.2.2. VARIABLE PARAMEERS OF THE FIELD TRIAL.
Section Fine Glass Fly Ash Type 1 WR Type / % of % of Total Type Total Aggr. Aggr-
1 None None None
2 FI/20% F3/20% High
3 FI/lO% F3/15% High
4 FI/20% F2/25% High
5 FI/20% F2/20% High
6 None F2/20% High
TABLE A3.2.3. VARIABLE PARAMETERS OF THE
POWDERED GLASS SERIES.
Batch Fine Glass Type Powdered Glass / % of Total % of Cement
Aggr-
W20%
None
None
FI/20%
W20%
FI/20%
FI/20%
FI/20%
None
None
None
1%
2.5%
5%
10%
20%
VARIABLE PARAMETERS OF THE ACCELERATED ASR EXPANSION MORTAR MIXES
TABLE A3.3.1. VARAIBLE PARAMETERS OF THE ACCELERATED ASR EXPANSION SERIES.
Mix No(s) Glass Type / % Fly Ash Type 1 % Powdered Glass w/(c +f) of Total Aggr of Total (c +f) % of Cement
None
FJ/100%
None
None
FJ/20%
FJ/10%
FJ/20%
FJ/100%
None
FJ/20%
FJ/20%
FJ/50%
None
FJ/5%
FJ/10%
FJ/20%
FJ/40%
FJl7O%
FJ/100%
None
None
None
F2/20%
F2/20%
F2/15%
F2/25%
None
F3/20%
F3/20%
F3/25%
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
TABLE A3.3.1. VARAIBLE PARAMETERS OF THE ACCELERATED ASR EXPANSION SERIES. (CONTINUED)
Mix No(s) Glass Type / % Fly Ash Type / % Powdered Glass wl(c +f) of Total Aggr of Total (c +f) % of Cement
80 1 FJ/40% None None 0.43
802 FJ/40% None 1% 0.43
803 FJ/40% None 2.5% 0.43
804 FJ/40% None 5% 0.43
805 FJ/40% None 10% 0.43
806 FJ/40% None 20% 0.43
1204 FJ/20% None 1% 0.43
1205 FJ/20% None 2.5% 0.43
1206 FJ/20% None 5% 0.43
1207 FJ/20% None 10% 0.43
1208 FJ/20% None 20% 0.43
APPENDIX 4.1
MIX AND FRESH CONCRETE RESULTS
TABLE 4.1.1. GLASS-FLY ASH SERIES MIX AND FRESH CONCRETE RESULTS.
Batch(s) WI(C +f) (mm) (kg/m3) Air ( m ~ m ~ / l % ~ i r ) Slump Unit Wt. Content AE Admx.
TABLE A4.1.1. GLAss-FL,~' ASH SERIES MIX AND FRESH C O N C ~ RESULTS. (co-1
Batch(s) WI(C +fi (mm> (kg/m3> Air (mvrn3/l% ~ i r ) Slump Unit Wt. Content AE Admx.
TABLE A4.1.1. GLASS-FLY ASH SERIES MIX AND FFESH CONCRE~E RESULTS. ( c o r n )
Batch(s) WI(C +fi (mm> (kg/m3> Air ( m ~ m ~ / l % '0) Slump Unit Wt. Content AE Admx.
TABLE A4.1.2. FIELD RUAL MIX AND FRESH CONCRETE RESULTS.
Section wl(c +J) (mm> (kg/m3) Air (mum3/l % ~ i r > Slump Unit Wt. Content AE A h .
1 0.49 90 2294 7.0% 48
A4.1.3. POWDERED GLASS SERIES MIX AND FRESH CONCREIE RESULTS.
Batch(s) WI(C +J) (m) (kg/m3) Air (mum3/l % ~ i r ) Slump Unit Wt. Content AE Admx.
AU compressive strength results are adjusted to a nominal entrained air content of 6.0%.
Tabulated values are averages of several specimens.
TABLE A4.2.1. GLASS-FLY ASH SERIES COMPRESSIVE STRENGTH RESULTS.
Batch No(s). Strength (MPa) at Age (days):
7 2 8 90 180 365
TABLE A4.2.1. GLASS-FLY ASH SERIES COMPRESSIVE STRENGTH RESULTS. (CONTINUED)
Batch No(s). Strength (MPa) at Age (days):
All compressive strength results are adjusted to a nominal entrained air content of 6.0%.
Tabulated values are averages of several specimens.
Section Strength (MPa) at Age (days):
7 28 90 180 365
All compressive strength results are adjusted to a nominal entrained air content of 6.0%.
Tabulated values are averages of several specimens.
Section Strength (MPa) at Age (days):
7 28 120 3 65
All compressive strength results are adjusted to a nominal entrained air content of 6.0%.
Tabulated values are averages of several specimens.
Batch(s) Strength (MPa) at Age (days):
7 14 28 5 6 90
Section Strength (MPa) at Age (days):
2 8 120 365
Mix No. Strength (MPa) at Age (days):
7 14 28 56 90
APPENDE 4.4
CONCRETE PRISM ASR EXPANSION RESULTS
TABLE A4.4.1. GLASS-FLY ASH SERIES CONCRETE PRISM ASR EXPANSION RESULTS.
Batch No(s). Prism Expansion (x0.00 1 %) at Age (days):
7 28 112 365 730 1095
0 0 0 0 0
NIA NIA NIA NIA NIA
NIA NIA NIA NIA NIA
NIA NIA NIA NIA NIA
4 1 0 0 0
I1 8 6 3 0
4 6 9 13 16
4 6 7 8 9
3 4 5 6 6
3 10 18 2 1 25
2 5 8 10 11
0 0 24 5 8 106
3 5 11 16 18
5 6 12 17 20
4 6 10 13 15
5 22 40 118 305
6 9 3 2 110 265
8 11 14 18 2 1
0
NIA
TABLE A4.4.1. GLASS-FLY ASH SERIES CONCRETE PRISM ASR EXPANSION RESLTLTS . (CONTINUED)
Batch No(s). Prism Expansion (~0 .001%) at Age (days):
7 28 112 365 730 1095
TABLE A4.4.1. GLASS-FLY ASH SERIES CONCRETE PRISM ASR EXPANSION RESULTS. (CONTINUED)
Batch No(s). Prism Expansion (x0.00 1 %) at Age (days):
7 28 112 365 730 1095
TABLE A4.4.2. FIELD TRIAL CONCRETE PRISM ASR EXPANSION RESULTS.
Section Prism Expansion (~0.001%) at Age (days):
7 14 28 56 112 224 365
F'REEZE/THAW RESULTS
TABLE A4.5.1. STIFFNESS R E T ~ BY GLASS-FLY &H SERIES DURING Ffl TESTING.
Batch(s) (GPa) St f iess Retained (%) at Age (cycles): Initial D Y ~ E
TABLE A4.5.2. WHGH~ REZNNED BY GLASS-FLY ASH SERIES DURING Fm TESTING.
Batch(s) (kg) Weight Retained (%) at Age (cycles): Initial
Weight
TABLE A4.5.3. STIFFNESS RETAINED BY FIELD TRIAL DURING F/T TESTING.
Section (MPa) Stfiess Retained (%) at Age (cycles): Initial
D Y ~ E
TABLE A4.5.4. WEIGHT RETAINED BY FIELD TRIAL DURING F/T TESTING.
Section (kg) Weight Retained (%) at Age (cycles): Initial
Weight
TABLE A4.5.5. STIFFNESS RETAINED BY POWDERED GLASS SERTES DURING Fm TESTING.
Batch (hPa) Stf iess Retained (%) at Age (cycles): Initial D Y ~ E
Batch (kg) Weight Retained (%) at Age (cycles): Initial
Weight
APPENDIX 4.6
ACCELERATED ASR EXPANSION RESULTS
TABLE A4.6.1. ACCEEMT'F,D ASR EXPANSION RESULTS.
Batch Expansion (~0.001%) at Age (days):
1 3 5 7 9 11 13 14
Recommended