Concrete aggregate durability study

              Concrete Aggregate
Durability Study
Final Report 575
Prepared by:
Thomas Van Dam, Ph. D., P. E.
David Peshkin, P. E.
Applied Pavement Technology, Inc.
115 W. Main St., Suite 400
Urbana, IL 61801
June 2009
Prepared for:
Arizona Department of Transportation
in cooperation with
U. S. Department of Transportation
Federal Highway Administration
The contents of this report reflect the views of the authors who are responsible for the facts and
the accuracy of the data presented herein. The contents do not necessarily reflect the official
views or policies of the Arizona Department of Transportation or the Federal Highway
Administration. This report does not constitute a standard, specification, or regulation. Trade or
manufacturers’ names which may appear herein are cited only because they are considered
essential to the objectives of the report. The U. S. Government and The State of Arizona do not
endorse products or manufacturers.
This report can also be found on our web site…
http:// www. dot. state. az. us/ ABOUT/ atrc/ Publications/ Publications. htm
Technical Report Documentation Page
1. Report No.
FHWA- AZ- 09- 575
2. Government Accession No.
3. Recipient's Catalog No.
4. Title and Subtitle 5. Report Date
June 2009
Concrete Aggregate Durability Study 6. Performing Organization Code
7. Author
Thomas Van Dam, Ph. D., P. E. and David Peshkin, P. E.
8. Performing Organization Report No.
9. Performing Organization Name and Address 10. Work Unit No.
Applied Pavement Technology, Inc.
115 W. Main St., Suite 400
Urbana, IL 61801
11. Contract or Grant No.
12. Sponsoring Agency Name and Address
ARIZONA DEPARTMENT OF TRANSPORTATION
206 S. 17TH AVENUE
13. Type of Report & Period Covered
PHOENIX, ARIZONA 85007
Project Manager: Christ Dimitropolos
14. Sponsoring Agency Code
15. Supplementary Notes
Prepared in cooperation with the U. S. Department of Transportation, Federal Highway Administration.
Paul Mueller, P. E., served as a consultant to the project team.
16. Abstract
There are many factors that affect the durability of Portland cement concrete ( PCC), including the mix design and the
materials used, the quality of construction, and the environment. Durability is not an intrinsic property of the concrete, but
instead is related to how the material interacts with the environment. Durability- related deterioration is referred to as
materials- related distress ( MRD). Common MRDs include those caused by physical processes, such as freezing and
thawing, or chemical processes, such as alkali- silica reactivity ( ASR) and sulfate attack. This research project was
undertaken to determine whether concrete used in the ADOT system is experiencing, or is potentially susceptible to, ASR or
sulfate attack, and if so, to what degree.
Based on this study, ADOT’s current practices are consistent with those of its neighboring states, but by no means are they
the most rigorous, particularly related to controlling ASR. The following recommendations are made to improve ADOT’s
approach to ASR and sulfate attack mitigation to ensure success in the future:
• ADOT should review its supplementary cementitious material ( SCM) specifications to ensure that those materials being
used in its concrete have the desired effect of mitigating ASR and sulfate attack.
• A number of neighboring states permit the use of ASTM C1157 performance- specified cements and ADOT should
investigate allowing the use of these cements as well.
• ADOT is following the current state- of- the- practice regarding aggregate screening for ASR susceptibility. New FHWA
guidelines ( Thomas et al. 2008A) recommend that long- term concrete prism testing be conducted in accordance with
ASTM C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali- Silica Reaction,
to establish an empirical relationship with the ASTM C1260 test results to ensure mitigation. This would require
ADOT to embark on a long- term study to test their most common ASR- susceptible aggregates, but it is the only
currently acceptable approach to developing confidence that the ASTM C1260/ C1567 results accurately predict field
performance.
17. Key Words
Alkali- silica reactivity, sulfate attack, concrete durability
18. Distribution Statement
Document is available to the
U. S. public through the
National Technical Information
Service, Springfield, Virginia
22161
23. Registrant's Seal
19. Security Classification
Unclassified
20. Security Classification
Unclassified
21. No. of Pages
55
22. Price
SPR- PL- 1- 965) 575
SI* ( MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol
LENGTH LENGTH
in inches 25.4 millimeters mm mm millimeters 0.039 inches in
ft feet 0.305 meters m m meters 3.28 feet ft
yd yards 0.914 meters m m meters 1.09 yards yd
mi miles 1.61 kilometers km km kilometers 0.621 miles mi
AREA AREA
in2 square inches 645.2 square millimeters mm2 mm2 Square millimeters 0.0016 square inches in2
ft2 square feet 0.093 square meters m2 m2 Square meters 10.764 square feet ft2
yd2 square yards 0.836 square meters m2 m2 Square meters 1.195 square yards yd2
ac acres 0.405 hectares ha ha hectares 2.47 acres ac
mi2 square miles 2.59 square kilometers km2 km2 Square kilometers 0.386 square miles mi2
VOLUME VOLUME
fl oz fluid ounces 29.57 milliliters mL mL milliliters 0.034 fluid ounces fl oz
gal gallons 3.785 liters L L liters 0.264 gallons gal
ft3 cubic feet 0.028 cubic meters m3 m3 Cubic meters 35.315 cubic feet ft3
yd3 cubic yards 0.765 cubic meters m3 m3 Cubic meters 1.308 cubic yards yd3
NOTE: Volumes greater than 1000L shall be shown in m3.
MASS MASS
oz ounces 28.35 grams g g grams 0.035 ounces oz
lb pounds 0.454 kilograms kg kg kilograms 2.205 pounds lb
T short tons ( 2000lb) 0.907 megagrams
( or “ metric ton”)
mg
( or “ t”)
mg megagrams
( or “ metric ton”)
1.102 short tons ( 2000lb) T
TEMPERATURE ( exact) TEMPERATURE ( exact)
º F Fahrenheit
temperature
5( F- 32)/ 9
or ( F- 32)/ 1.8
Celsius temperature º C º C Celsius temperature 1.8C + 32 Fahrenheit
temperature
º F
ILLUMINATION ILLUMINATION
fc foot candles 10.76 lux lx lx lux 0.0929 foot- candles fc
fl foot- Lamberts 3.426 candela/ m2 cd/ m2 cd/ m2 candela/ m2 0.2919 foot- Lamberts fl
FORCE AND PRESSURE OR STRESS FORCE AND PRESSURE OR STRESS
lbf poundforce 4.45 newtons N N newtons 0.225 poundforce lbf
lbf/ in2 poundforce per
square inch
6.89 kilopascals kPa kPa kilopascals 0.145 poundforce per
square inch
lbf/ in2
SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380
TABLE OF CONTENTS
EXECUTIVE SUMMARY ............................................................................................................ 1
CHAPTER 1. OVERVIEW........................................................................................................... 5
Introduction................................................................................................................... ............. 5
Project Objective...................................................................................................................... .. 5
Research Approach ..................................................................................................................... 6
CHAPTER 2. ALKALI- SILICA REACTIVITY .......................................................................... 7
Overview of ASR........................................................................................................................ 7
ASR Test Methods.................................................................................................................... 10
ASR Mitigation..................................................................................................................... ... 14
ASR in Arizona........................................................................................................................ 15
ASR Specifications in Arizona ................................................................................................. 16
1006- 2.01 Cement................................................................................................................. 16
1006- 2.02 Water ................................................................................................................... 16
1006- 2.03 Aggregates........................................................................................................... 17
1006- 2.04 Supplementary Cementitious Material ................................................................ 17
Comments on Arizona Specifications................................................................................... 18
ASR Specifications in Surrounding States ............................................................................... 18
Cement ............................................................................................................................... .. 18
Aggregate...................................................................................................................... ....... 18
Water.......................................................................................................................... .......... 18
Supplementary Cementitious Materials................................................................................ 19
Summary of ASR...................................................................................................................... 20
CHAPTER 3. SULFATE ATTACK............................................................................................. 21
Overview of Sulfate Attack ...................................................................................................... 21
Sulfate Attack Test Methods..................................................................................................... 22
Sulfate Attack Mitigation.......................................................................................................... 23
Sulfate Attack in Arizona.......................................................................................................... 24
Sulfate Attack Specifications in Arizona.................................................................................. 26
1006- 2.01 Cement................................................................................................................. 27
1006- 2.02 Water ................................................................................................................... 27
1006- 2.04 Supplementary Cementitious Material ................................................................ 27
1006- 3.01 Water- to- Cementitious Ratio ( w/ cm)................................................................... 28
Comments on Arizona Specifications................................................................................... 28
Sulfate Attack Specifications in Surrounding States ................................................................ 28
Cement ............................................................................................................................... .. 28
Water.......................................................................................................................... .......... 29
Supplementary Cementitious Materials................................................................................ 30
Water- to- Cementitious Material Ratio ( w/ cm) ..................................................................... 30
Summary of Sulfate Attack....................................................................................................... 30
CHAPTER 4. SUMMARY OF FINDINGS AND RECOMMENDATIONS ............................ 33
REFERENCES ............................................................................................................................. 37
APPENDIX - SUMMARY OF SPECIFICATIONS USED BY NEIGHBORING STATES
TO AID IN ASR AND SULFATE ATTACK MITIGATION......................................... 41
LIST OF FIGURES
Figure 1: Pattern cracking observed in a concrete pavement due to ASR...................................... 7
Figure 2: Cracking concentrated at joints in a concrete pavement due to ASR. ............................ 8
Figure 3. Cracking with white ASR exudate ( arrows) in cracks. ................................................... 8
LIST OF TABLES
Table 1. Some examples of commonly reactive aggregate and mineral types ( ACI 2008)............ 9
Table 2. ASR test methods ( Farny and Kerkhoff 2007). .............................................................. 12
Table 3. Summary of surrounding state concrete specifications related to ASR.......................... 19
Table 4. Summary of risk of concrete corrosion ( USDA 2008). .................................................. 25
Table 5. Summary of surrounding state concrete specifications as pertains to sulfate attack. ..... 29
1
EXECUTIVE SUMMARY
There are many factors that affect the durability of Portland cement concrete
( PCC), including the mix design and the materials used, the quality of construction,
and the environment. Durability is not an intrinsic property of the concrete, but
instead is related to how the material interacts with the environment. Durability-related
deterioration is referred to as materials- related distress ( MRD). Common
MRDs include those caused by physical processes, such as freezing and thawing
( F- T), or chemical processes, such as alkali- silica reactivity ( ASR) and sulfate
attack.
Although considered an issue in surrounding states, MRD in general, and ASR
and sulfate attack in particular, have not been formally identified in structures or
bridges managed by the Arizona Department of Transportation ( ADOT). Yet
there is ample reason to be concerned that durability could pose a problem for
ADOT’s PCC. A recent study of a 14- year old PCC pavement on a major airfield
in Arizona determined that significant ASR had occurred. Further, ASR has been
identified in many hydraulic structures in Arizona, including the Coolidge Dam,
Parker Dam, and Steward Dam. Since ASR is a reaction between susceptible
aggregates and the alkalis ( sodium and potassium) present in the concrete pore
solution, this suggests that MRD may be more of a concern to ADOT than pre-viously
believed. It is also well- documented that many of the soils in Arizona
have sufficient sulfate levels to pose a possible sulfate attack problem. Thus it
seems prudent that the possibility of ASR and sulfate attack in Arizona be
researched further.
This research project was undertaken to determine whether concrete used in the
ADOT system is experiencing, or is potentially susceptible to, ASR or sulfate
attack, and if so, to what degree. This objective was addressed through the
completion of the following four tasks:
• Task 1. Contact Arizona industries and local and federal agencies in
Arizona for published and unpublished experience with ASR/ sulfate
problems or suspected problems.
• Task 2. Review the history of cement production for cement used in
Arizona and the development of specifications used by ADOT for both
pavements and structures. Review the historical development of ADOT’s
aggregate specifications used in concrete.
• Task 3. Review specifications used in surrounding states and national
guidelines and compare them to ADOT’s specifications for mitigating the
impact of ASR and sulfate attack.
2
• Task 4. Prepare a report documenting the findings of the previous tasks
and identifying any needed specification changes to ADOT’s current
concrete specifications.
The findings of this study can be summarized as follows:
• Both ASR and sulfate attack can potentially impact concrete transportation
structures in Arizona, although little evidence exists that links either
mechanism to degradation in newly constructed pavements or bridges.
• In particular, there is little immediate concern over ASR, although it is
known that reactive aggregates can be found over a broad geographic area
including in the vicinity of the Salt ( and possibly the Gila) River and along
the Santa Cruz River. ADOT has likely avoided obvious ASR problems
through the routine use of relatively low alkali cement ( 0.60 percent
Na2Oeq) and the use of low CaO content Class F fly ash ( at 25 to 32
percent replacement for cement). ADOT makes allowance for the use of
blended Portland- pozzolan cement ( ASTM C 595 Type IP ( MS)), which
would also likely be effective at mitigating ASR.
• The relatively recent addition of aggregate screening testing to the ADOT
specification in accordance with ASTM C1260, Standard Test Method for
Potential Alkali Reactivity of Aggregates ( 14- day expansion limit of 0.10
percent), is a good step in identifying susceptible aggregates. Mitigation
of potentially reactive aggregates follows the current state of the practice,
requiring testing using ASTM C1567, Standard Test Method for Deter-mining
the Potential Alkali- Silica Reactivity of Combinations of Cementi-tious
Materials and Aggregate, in which the cementitious system is a
blend of the Portland cement and supplementary cementitious materials
( SCMs) to be used in the job mix.
• Although ADOT now requires aggregate screening, many of the surrounding
states have more detailed guidance in their specifications related to the use
of SCMs, either as a replacement for or as an addition to Portland cement.
New Mexico has the most rigorous approach to mitigate ASR using
SCMs, whereas Texas provides numerous options for blending various
SCMs. Guidance associated with the use of SCMs includes limiting
available alkalis in the mix, specifying the addition of pozzolans ( 20 to 25
percent minimum), and limiting the CaO content of the fly ash ( 8 to 15
percent maximum). Although not a supplementary material, it is noted
that some states also allow the use of lithium- based admixtures to mitigate
ASR.
• The potential for sulfate attack exists over a wide geographical area, with 6.9
and 5.9 percent of the surface area of Arizona considered as having
moderate to high potential for concrete corrosion ( including sulfate
3
attack), respectively. ADOT specifies either Type II or V cements, which
have moderate or high resistance to sulfate attack, respectively. Further,
there is allowance for the use of blended Portland- pozzolan cement
( ASTM C 595 Type IP ( MS)) which would likely be effective at
mitigating sulfate attack.
• The significantly expanded section in the ADOT specifications on SCMs
allows a much broader category of materials to be considered, but few
limits are placed. Sulfate attack is addressed by testing cement/ SCM
blends through use of ASTM C1012, applying expansion limits of 0.10
percent at 6 months for moderate sulfate resistance and 0.05 percent at 6
months and 0.10 percent at 1 year for high sulfate resistance. Since the
maximum allowable replacement of Portland cement with an SCM is 25
percent, resistance to sulfate attack is not ensured, but there is provision
for the use of additional SCMs if mitigation is sought.
• ADOT’s approach to mitigating sulfate attack is consistent with that of most
surrounding states, which also specify the use of Type II and V cements.
Further, guidance associated with the use of supplementary cementitious
materials for addressing sulfate attack includes specifying the addition of
pozzolans ( 20 to 25 percent minimum), limiting the CaO content of the fly
ash ( 8 to 15 percent maximum), and the use of ASTM C1012, Standard
Test Method for Length Change of Hydraulic- Cement Mortars Exposed to
a Sulfate Solution expansion testing.
Based on this study, ADOT’s current practices are consistent with that of its
neighboring states, but by no means are they the most rigorous, particularly
related to controlling ASR. The following recommendations are made to improve
ADOT’s approach to ASR and sulfate attack mitigation to ensure success in the
future:
• Although ADOT has benefited from abundant sources of low CaO Class F
fly ash, it is important to recognize that fly ash characteristics are
changing as the coal source, combustor technology, collection
methodology, and increasing environmental demands change. Thus there
is no assurance that the effectiveness of the fly ash ADOT is currently
using will be maintained in perpetuity. ADOT should review its SCM
specifications to ensure that those materials being used in its concrete have
the desired effect of mitigating ASR and sulfate attack. Of the
specifications reviewed, those currently employed by New Mexico’s
highway department are the most thorough.
• For the most part, ADOT’s specifications for cement are similar to those of
the surrounding states with one exception: a number of neighboring states
also permit the use of ASTM C1157 performance- specified cements.
ADOT should investigate allowing the use of these cements as well.
4
• With regards to aggregate screening for ASR, ADOT is following the current
state- of- the- practice utilizing accelerated mortar bar testing in compliance
with ASTM C1260/ C1567. This testing protocol has some limitations, but
its short duration ( 16 days from casting to completion) makes it extremely
attractive for project use. The new FHWA guidelines ( Thomas et al.
2008A) recommend that long- term concrete prism testing be conducted in
accordance with ASTM C1293, Standard Test Method for Determination
of Length Change of Concrete Due to Alkali- Silica Reaction, to establish
an empirical relationship with the ASTM C1260 test results to ensure
mitigation. This would require ADOT to embark on a long- term study to
test its most common ASR- susceptible aggregates, but it is the only
currently acceptable approach to developing confidence that the ASTM
C1260/ C1567 results accurately predict field performance.
5
CHAPTER 1.
OVERVIEW
Introduction
The durability of Portland cement concrete ( PCC) has long been identified as a
problem by the transportation community. There are many factors that affect the
durability of PCC, including the mix design and the materials used, the quality of
construction, and the environment. Durability is not an intrinsic property of the
concrete, but instead is related to how the material interacts with the environment.
As a result, deterioration that results from durability is now referred to as
materials- related distress ( MRD). Common MRDs include those caused by
physical processes such as freezing and thawing ( F- T) in a saturated state ( paste
F- T damage and aggregate F- T damage) or as a result of salt crystallization
( physical salt attack) or chemical processes including alkali- aggregate reactivity
( including alkali- silica reactivity ( ASR) and alkali- carbonate reactivity), sulfate
attack, and chemical deicer attack. It is known that MRD affects a large
percentage of PCC pavements in certain geographical regions of the United
States.
Although considered an issue in surrounding states, MRD in general, and ASR
and sulfate attack in particular, have not been formally identified in structures or
bridges managed by the Arizona Department of Transportation ( ADOT). Yet
there is ample reason to be concerned that durability could pose a problem for
ADOT’s PCC. A recent study of a 14- year old PCC pavement on a major airfield
in Arizona determined that significant ASR had occurred. Further, ASR has been
identified in many hydraulic structures in Arizona, including the Coolidge Dam,
Parker Dam, and Steward Dam. Since ASR is a reaction between susceptible
aggregates and the alkalis ( sodium and potassium) present in the concrete pore
solution, MRD may be more of a concern to ADOT than previously believed. It
is also well- documented that many of the soils in Arizona have sufficient sulfate
levels to pose a possible sulfate attack problem. Unfortunately, these problems
typically take many years to manifest themselves and once detected, corrective
action is often times difficult to undertake; because of this, prevention is the best
solution. Thus it seems prudent that the possibility of ASR and sulfate attack in
Arizona be researched further.
Project Objective
Under ADOT Project 575, research was undertaken to address the objective of
determining whether concrete used in the ADOT system is experiencing, or is
potentially susceptible to, ASR or sulfate attack, and if so, to what degree. The
approach that was followed to make this determination is described below.
6
Research Approach
The project objectives were met by carrying out the following four tasks:
• Task 1. Contact Arizona industries and local and Federal agencies in
Arizona for published and unpublished experience with ASR/ sulfate
problems or suspected problems.
• Task 2. Review the history of cement production for cement used in
Arizona and the development of specifications used by ADOT for both
pavements and structures. Review the historical development of ADOT’s
aggregate specifications used in concrete.
• Task 3. Review specifications used in surrounding states and national
guidelines and compare them to ADOT’s specifications for mitigating the
impact of ASR and sulfate attack.
• Task 4. Prepare a report documenting the findings of the previous tasks
and identifying any needed specification changes to ADOT’s current
concrete specifications.
7
CHAPTER 2.
ALKALI- SILICA REACTIVITY
Overview of ASR
ASR is a deterioration mechanism in concrete which can cause serious expansion
and cracking resulting in major structural damage. ASR progresses in a number of
stages, and is not considered deleterious until the concrete is damaged by the
reaction ( Thomas et al. 2008A). The reaction initiates when available hydroxyl
ions ( OH- present in the alkaline pore solution to balance the charge contributed
by the positively charged alkali ions of sodium ( Na+) and potassium ( K+)) decom-pose
certain siliceous components of reactive aggregates. This frees the silica to
react with the alkali to form the alkali- silica reaction product, or gel. As this gel
imbibes water, it swells. It is believed that the swelling of this gel alone does not
cause damage, as it has relatively low viscosity and therefore moves readily
through the concrete pore network into available space. But as this gel reacts with
calcium present in the cement paste, it becomes more viscous and stresses
develop, exerting an expansive pressure inside concrete. At a certain point, this
pressure exceeds the tensile strength of the aggregate and/ or concrete and crack-ing
initiates. ASR causes a characteristic pattern cracking in concrete as shown in
Figure 1. At times, it has also been observed to more severely affect joints, as
shown if Figure 2, due to the localized increased availability of water. Figure 3
clearly shows the gel product exuding onto the pavement surface through cracks.
Figure 1: Pattern cracking observed in a concrete pavement due to ASR.
8
Figure 2: Cracking concentrated at joints in a concrete pavement due to ASR.
Figure 3. Cracking with white ASR exudate ( arrows) in cracks.
9
It is widely accepted that the following three essential components are necessary
for ASR- induced damage to occur in a concrete structure:
• Reactive aggregates – Reactive aggregates typically fall into one of two
categories: 1) poorly crystalline or metastable silica materials, and 2)
certain varieties of quartz. Note that ASR can even occur in limestone that
contains reactive siliceous components ( ACI 2008). Table 1 summarizes
common examples of reactive rocks and minerals. For deleterious ASR to
occur, sufficient reactive aggregate must be present to cause damage.
Table 1. Some examples of commonly reactive aggregate
and mineral types ( ACI 2008).
Rocks Minerals
Shale
Sandstone
Silicified
carbonate rock
Flint
Argillite
Greywacke
Arenite
Hornfels
Chert
Quartzite
Quartz- arenite
Gneiss
Granite
Siltstone
Arkose
Opal
Tridymite
Crisobalite
Cryptocrystalline/ microcrystalline
Quartz
Strained quartz
Volcanic glass
• Water – Deleterious ASR will not occur if water is not available within the
concrete, since the expansion of ASR gel requires water. Available mois-ture
is critical in considering a structure’s susceptibility to ASR distress. In
very dry environments, concrete made with highly reactive aggregates and
high alkali cement may not exhibit deleterious expansion due to ASR.
Even within a structure there may be varying amounts of expansion de-pending
on exposure conditions. Unfortunately, concrete in contact with
the ground, such as that within pavements and many transportation struc-tures,
will often maintain the minimum relative humidity of 80 percent
required to cause significant expansion due to ASR. As a result, keeping a
transportation structure “ dry” is not considered a viable mitigation strategy
to address ASR.
• Sufficient alkalis – Alkalis present in concrete pore solution can be con-tributed
by the Portland cement, other constituents ( e. g., aggregates, fly
ash, slag, and silica fume), or may enter the concrete over time from ex-ternal
sources, such as deicing salts or ground water containing sulfates.
The primary contributor is the alkalis in Portland cement. The alkali
content of cement is expressed as “ equivalent alkali content” ( Na2Oeq),
determined by the following expression:
Na2Oeq = Na2O + ( 0.685 × K2O)
10
where sodium oxide ( Na2O) and potassium oxide ( K2O) contents are
expressed as percentages on the cement mill certificate. The use of low
alkali cement (< 0.60 percent Na2Oeq) is commonly cited as an effective
mitigation strategy, yet it is better to calculate the total alkali loading in
the mixture which accounts for the cement content as well as the addition
of other components which may contribute alkalis ( ACI 2008). Recently
it has been concluded that limiting alkalis may be insufficient to mitigate
ASR if highly reactive aggregates are present ( Folliard et al. 2006).
The deleterious expansion associated with ASR gel formation and resulting pres-sure
are still not fully understood. The first theory developed attributed the
damage to the formation of osmotic pressure cells as water is imbibed, cracking
the mortar structure ( Hansen 1944). A second theory proposed that water is
absorbed by the alkali- silica gel, swelling the gel and stressing the mortar struc-ture
( McGowan and Vivian 1952). And a third theory accounts for both previous
theories’ mechanisms, resulting in cracking depending on alkali- silicate complex
( Powers and Steinor 1955). One aspect involving ASR and expansion that has
received renewed interest in recent years is the important role of calcium.
Although early proposed mechanisms ( Hansen 1944; McGowan and Vivian 1952)
did not recognize calcium's role in ASR, later studies have identified the presence
of calcium in the reactive system as being essential to the deleterious process.
Diamond ( 1989) proposed that, in the absence of calcium, silica simply dissolves
in alkali- hydroxide solution and does not form alkali- silicate gel. Most recently,
it has been proposed that in the absence of calcium, the gel formed is highly fluid
and damage will only occur once the gel viscosity increases as it reacts with
calcium from the cement paste ( Ichikawa 2007).
ASR Test Methods
The current state- of- the- practice with regards to ASR testing has recently been
published by the Federal Highway Administration ( FHWA) ( Thomas et al.
2008A). This document details the recommended test methods, procedures, and
strategies for mitigating ASR.
The most widely used and accepted test methods for assessing the ASR potential
of aggregates is ASTM C1260, Standard Test Method for Potential Alkali Reac-tivity
of Aggregates. This test is also called the accelerated mortar bar test
( AMBT). It is an empirical test in which mortar bars made with the aggregate
source in question are immersed in a 1 M NaOH solution at 176oF ( 80oC) for a
minimum of 14 days. According to the recently released FHWA guidance
( Thomas et al. 2008), if the expansion does not exceed 0.10 percent at 14 days,
the aggregate is considered non- deleteriously reactive. If the 14- day expansion
exceeds 0.10 percent, the aggregate should be considered potentially reactive and
tested in accordance with ASTM C 1293 as discussed later. A variation of this
test is ASTM C1567, Standard Test Method for Determining the Potential Alkali-
Silica Reactivity of Combinations of Cementitious Materials and Aggregate,
11
which is used to test the effectiveness of supplementary cementitious materials
( SCMs), such as fly ash and slag, or lithium- based admixtures in mitigating ASR.
The AMBT has the advantage of being a relatively quick test that is easy to
conduct with simple equipment. This allows the rapid assessment of aggregate
sources without a large capital investment. But it does have a number of
problems associated with it. One problem with this test is that it is considered
severe for many aggregate types, rating aggregates as potentially reactive even
though they may perform well in service. For example, some have recommended
that the expansion limit of 0.10 percent is acceptable for quarried silicate and
siliceous carbonate rocks, but should be adjusted to 0.20 percent for natural sands
and gravels ( Bérubé and Fournier 1992). Others have argued that the 14- day test
yields too many false negatives, predicting good performance when in actuality
failure results in field specimens ( Stokes 2006). It was recommended that the test
duration be extended to 28 days, keeping the failure criteria the same. After a
thorough review of the available data, one study has suggested that a 14- day
expansion criteria of 0.06 percent yields the same result as an expansion criteria
of 0.13 percent at 28 days, avoiding the false negatives while minimizing false
positives ( when an aggregate is rejected for use even though it would have good
field performance) ( Malvar and Lenke 2008). Clearly more work is needed on
establishing test duration and criteria for the AMBT.
As mentioned, if an aggregate is found to be potentially deleteriously reactive
based on ASTM C1260, it is recommended that it be tested in accordance with
ASTM C 1293, Standard Test Method for Concrete Aggregates by Determination
of Length Change of Concrete Due to Alkali- Silica Reaction. This test method is
commonly referred to as the concrete prism test ( CPT) and it is generally con-sidered
the most accurate test in predicting the field performance of aggregates
( Folliard, Thomas, and Kurtis 2003) although some recent work has called this
into question. In the test, concrete prisms are made at an increased alkali content
and suspended above water at 100oF ( 38oC) for 1 year. Expansion is measured
periodically and if it does not exceed 0.04 percent at one year, the aggregate is
considered non- deleteriously reactive. If this test method is being used to assess
the effectiveness of a mitigation strategy such as the use of fly ash, slag, or
lithium- based admixture, the test duration is extended to 2 years. The long test
duration of this test method has somewhat limited its use ( Folliard, Thomas, and
Kurtis 2003).
While there are a variety of other test methods available ( see Table 2), the two
mentioned above are the most common for identifying potentially reactive
aggregate and form the basis for almost all current ASR test methods employed
by state departments of transportation.
12
Table 2. ASR test methods.
Test Name Purpose Type of Test Test Duration Comments
ASTM C 227,
Potential alkali-reactivity
of
cement- aggregate
combinations
( mortar- bar
method)
To test the
susceptibility of
cement- aggregate
combinations to
expansive reactions
involving alkalis
Mortar bars stored
over water at 37.8° C
( 100° F) and high
relative humidity
Varies: first
measurement at 14
days, then 1, 2, 3,
4, 6, 9, and 12
months; every 6
months after that as
necessary
Test may not produce
significant expansion,
especially for carbonate
aggregate. Long test
duration. Expansions may
not be from alkali-aggregate
reactivity.
ASTM C 289,
Potential alkali-silica
reactivity of
aggregates
To determine
potential reactivity
of siliceous
aggregates
Sample reacted with
alkaline solution at
80° C ( 176° F).
24 hours Quick results. Some
aggregates give low
expansions even though
they have high silica
content. Not reliable.
ASTM C 295,
Petrographic
examination of
aggregates for
concrete
To outline
petrographic
examination
procedures for
aggregates— an aid
in determining their
performance
Visual and
microscopic
examination of
prepared samples—
sieve analysis,
microscopy, scratch
or acid tests
Short duration—
visual examination
does not involve
long test periods
Usually includes optical
microscopy. Also may
include XRD1 analysis,
differential thermal
analysis, or infrared
spectroscopy— see ASTM
C 294 for descriptive
nomenclature. Important
to have an experienced
petrographer perform the
examination.
ASTM C 342,
Potential volume
change of cement-aggregate
combinations
To determine the
potential ASR
expansion of
cement- aggregate
combinations
Mortar bars stored
in water at 23° C
( 73.4° F)
52 weeks Primarily used for
aggregates from
Oklahoma, Kansas,
Nebraska, and Iowa.
ASTM C 441,
Effectiveness of
mineral admixtures
or GBFS2 in
preventing
excessive
expansion of
concrete due to
alkali- silica
reaction
To determine
effectiveness of
supplementary
cementing materials
in controlling
expansion from
ASR
Mortar bars— using
Pyrex glass as
aggregate— stored
over water at 37.8° C
( 100° F) and high
relative humidity
Varies: first
measurement at 14
days, then 1, 2, 3,
4, 5, 9, and 12
months; every 6
months after that as
necessary
Highly reactive artificial
aggregate may not
represent real aggregate
conditions. ( Pyrex
“ releases significant
amounts of alkali,”
promoting reaction.
Unlike natural aggregates
which “ rarely release
significant amounts of
alkalis into concrete”
( Rogers and Hooton
1991).
ASTM C 856,
Petrographic
examination of
hardened concrete
To outline
petrographic
examination
procedures for
hardened concrete—
useful in
determining
condition or
performance
Visual
( unmagnified) and
microscopic
examination of
prepared samples
Short duration—
includes
preparation of
samples and visual
and microscope
examination
Specimens can be
examined with stereo
microscopes, polarizing
microscopes,
metallographic
microscopes, and
scanning electron
microscope. Important to
have an experienced
petrographer perform the
examination.
13
Table 2 ( continued). ASR test methods
Test Name Purpose Type of Test Test Duration Comments
ASTM C 856
( AASHTO T 299),
Annex uranyl-acetate
treatment
procedure
To identify products
of ASR in hardened
concrete
Staining of a
freshly- exposed
concrete surface and
viewing under UV
light
Immediate results Identifies small amounts
of ASR gel whether
causing expansion or not.
Opal, a natural aggregate,
and carbonated paste can
glow - interpret results
accordingly. Tests must
be supplemented by
petrographic examination.
Los Alamos
staining method
To identify products
of ASR in hardened
concrete.
Staining of a
freshly- exposed
concrete surface
with two different
reagents
Immediate results Identifies small amounts
of ASR alkali- rich gel
whether causing
expansion or not. Non-deleterious
gel can stain
positive - interpret results
accordingly. Tests must
be supplemented by
petrographic examination.
ASTM C 1260
( AASHTO T303),
Potential alkali
reactivity of
aggregates ( mortar-bar
method)
To test the potential
for deleterious
alkali- silica reaction
of aggregate in
mortar bars
Immersion of mortar
bars in alkaline
solution at 80° C
( 176° F)
16 days Very fast alternative to C
227. Useful for slowly
reacting aggregates or
those that produce
expansion late in the
reaction.
ASTM C 1293,
Determination of
length change of
concrete due to
alkali- silica
reaction ( concrete
prism test)
To determine the
potential ASR
expansion of
cement- aggregate
combinations.
Concrete prisms
stored over water at
38° C ( 100.4° F)
Varies: first
measurement at 7
days, then 28and
56 days, then
3,6,9, and 12
months; every 6
months as after that
as necessary
Preferred method of
assessment. Best
represents the field.
Requires long test
duration for meaningful
results. Use as a
supplement to C 227, C
295, C 289, and C 1260.
ASTM C 1567,
Potential alkali-silica
reactivity of
combinations of
cementitious
materials and
aggregate
( accelerated
mortar- bar method)
To test the potential
for deleterious
alkali- silica reaction
of cementitious
materials and
aggregate
combinations in
mortar bars
Immersion of mortar
bars in alkaline
solution at 80° C
( 176° F)
16 days Very fast alternative to C
1293. Allows evaluation
of effectiveness of
supplementary
cementitious materials.
Supplementary Test Methods
ASTM C 294,
Constituents of
natural mineral
aggregates
To give descriptive
nomenclature for the
more common or
important natural
minerals— an aid in
determining their
performance
Visual identification Short duration— as
long as it takes to
visually examine
the sample
These descriptions are
used to characterize
naturally- occurring
minerals that make up
common aggregate
sources.
( Source: Farny and Kerkhoff 2007)
1 XRD is X- ray diffraction.
2 GBFS is ground blast furnace slag cement.
14
ASR Mitigation
There is considerable recent information on strategies to mitigate ASR in new
construction ( Farny and Kerkhoff 2007, ACI 2008, Thomas et al. 2008A). The
primary methods for mitigating ASR in new concrete construction can be
categorized as follows:
• Prescreen aggregate sources and eliminate the use of potentially reactive
aggregates.
• Control/ limit the alkali content in the concrete.
• Use supplementary cementitious materials ( e. g., ground slag, fly ash,
natural pozzolan, and silica fume) or alkali- silica reactivity inhibiting
admixtures ( lithium- based).
In the new FHWA report, specific guidance is provided on how to approach ASR
mitigation in a prescriptive manner ( Thomas et al. 2008A). The first step is to
establish the aggregate reactivity class from the results of the CPT. Based on the
aggregate reactivity class and the size of the concrete structure and exposure
condition, a level of ASR risk is established. The level of prevention required is
then determined from the level of ASR risk and importance of the concrete
structure under consideration. From this prevention level, acceptable preventive
measures are selected.
In the case where the aggregate is non- deleteriously reactive, no mitigation is
required. In some cases where mitigation is required, ASR can be effectively
mitigated by limiting the alkali content of the concrete ( either in lbs/ yd3 or kg/ m3
Na2Oeq) or through the effective use of SCMs. In severe cases, both limiting the
total alkalis and the use of SCMs are required ( Thomas et al. 2008A).
Additional guidance for mitigating ASR can also be found in other sources ( Farny
and Kerkhoff 2007, ACI 2008). Although not addressed in the new FHWA report,
several documents provide guidance on using lithium admixtures to control ASR
( Folliard et al. 2003, Farny and Kerkhoff 2007). Also, natural pozzolans have been
found to be effective at mitigating ASR ( ACI 2008). In all cases, the use of ASTM
C1567 and C1293 can be used to determine the effectiveness of mitigation.
On a final note, it is important to understand that the ability of SCMs to mitigate
ASR is highly dependent on the nature of the SCM. Typically, fly ash is added as a
replacement for cement or as an addition at a rate of 15 to 40 percent to mitigate
ASR. In general, Class F fly ash is much more effective than Class C fly ash in
providing mitigation. Further, the CaO content of the fly ash is considered to be
very important, with limits of 8, 15, or 18 percent being common. The maximum
allowable alkali content of the fly ash is also commonly established ( Malvar et al.
2008). As the CaO and alkali content of a fly ash increases, its ability to mitigate
ASR decreases – in some cases it may even make ASR worse. Slag cement is also
commonly used as a replacement for, or as an addition to the cement at a rate of 25
to 65 percent.
15
ASR in Arizona
A preliminary review of this problem with representatives of the concrete industry
and public agency personnel indicates little immediate concern over ASR in
Arizona. In general, there is a perception that the ASR problems center on a
geographic area along the Salt River ( and possibly the Gila River). The Phoenix
metropolitan area is particularly affected. A number of structures in that area
show some signs of MRD, but due to the long- term nature of the the MRD
distress, few local structures have shown signs of distress that cause ADOT
concern. While ASR has manifested itself on the upper reaches of the Salt River,
where dams built and maintained by the Salt River Project are located, the
difference between these two locations probably is related to the constant
availability of moisture at the dam sites.
In a recent United States Geological Survey report, alluvial fans along the Santa
Cruz River were analyzed for suitability as aggregate ( Lindsey and Melick
undated). It was found that gravel derived from the Tucson, Sierrita, and Tuma-cacori
Mountains is composed mostly of volcanic rock, much of which is felsic in
composition, and may be susceptible to ASR. In particular, the felsic volcanic
composition of the Tucson Mountains gravel would likely indicate the presence of
abundant unstable silica minerals and volcanic rocks from the Sierrita Mountains
which include a high percentage of rhyolite crystal tuff and subordinate crystal-poor
ignimbrite would require mitigation for ASR. The U. S. Air Force also
cautions that glassy to crptocrystalline rhyolite to andesite volcanics and cherts
may be encountered in the basin and range areas of the western U. S. including
Arizona ( Air Force 2006).
From this information, it seems reasonable to conclude that ASR is a potential
problem for large areas of Arizona. ADOT has likely been fortuitous in avoiding
obvious ASR problems due to standard use of relatively low alkali cement,
standard use of fly ash, and the dry climatic conditions.
Regarding cement, the potential for an ASR problem was recognized early by the
Portland cement producers in Arizona. Since the construction of the Glen Canyon
Dam on the Colorado River in northern Arizona in 1960, the production of an
ASTM Type II, low alkali cement has been standard practice. Cements used in
Arizona that are produced in California and Mexico adhere to this requirement.
More importantly than the cement is the fact that fly ash is being used by ADOT
in all PCC at a replacement/ addition rate of 25 to 32 percent. For the most part,
these are Class F fly ashes with CaO contents below 6 percent which makes them
extremely effective in mitigating ASR. Phoenix Sky Harbor has a lot of old ASR
problems in aprons that were constructed prior to the use of these fly ash limits.
Fly ash has been used on all new pavements and there are no known ASR prob-lems.
It is important to recognize that fly ash characteristics are always changing
due to changes in coal source, combustor technology, collection methodology,
and increasing environmental demands. Thus there is no assurance that the
16
effectiveness of the fly ash will be maintained into perpetuity and thus ADOT
might want to evaluate its specifications to ensure future performance matches
current good performance.
And finally, there is no question that Arizona has benefited from dry climatic
conditions, as there is very little moisture available to drive ASR.
ASR Specifications in Arizona
Section 1006 ( dated February 20, 2007) of the Arizona DOT specifications was
reviewed as it pertains to ASR as well as other durability concerns. The
following relevant sections have been extracted from the specifications.
Underlined passages are new since the 2000 edition of the Standard
Specifications for Road and Bridge Construction.
1006- 2.01 Cement
Hydraulic cement shall consist of either Portland1 cement or Portland- pozzolan
cement. Portland cement shall conform to the requirements of ASTM C 150 for
Type II, III, or V. However, at the option of the manufacturer, processing
additions may be used in the manufacture of the cement, provided such
processing additions have been shown to meet the requirements of ASTM C 465,
and the total amount of such material used does not exceed one percent of the
weight of the Portland cement clinker.
Portland- pozzolan cement shall conform to the requirements of ASTM C 595 for
Type IP ( MS).
Hydraulic cement shall not contain more than 0.60 percent total alkali. The word
alkali as used in these specifications shall be taken as the sum of sodium oxide
and potassium oxide calculated as sodium oxide ( i. e., equivalent alkali content,
Na2Oeq).
1006- 2.02 Water
The water used shall be free from injurious amounts of oil, acid, alkali, clay,
vegetable matter, silt or other harmful matter. Water shall contain not more than
1,000 ppm of chlorides as Cl and not more than 1,000 ppm of sulfates as SO4.
Water shall be sampled and tested in accordance with the requirements of
AASHTO T 26. Potable water obtained from public utility distribution lines will
be acceptable.
1 Note that in the ADOT specification, “ Portland” is capitalized. In most U. S. literature, including
that published by the ACI, AASHTO, and ASTM, portland is not capitalized in portland cement.
17
1006- 2.03 Aggregates
When concrete is to be placed at elevations above 4,500 feet, the fine and coarse
aggregate shall be subject to five cycles of the sodium sulfate soundness test in
accordance with the requirements of AASHTO T 104. The total loss shall not
exceed 10 percent by weight of the aggregate as a result of the test. Tests for
soundness may be waived when aggregates from the same source have been
approved and the approved test results apply to the current production from that
source.
When aggregates show potential for alkali silica reaction ( ASR), as indicated by
expansions of 0.10 percent or greater at 16 days after casting when tested in
accordance with ASTM C 1260, sufficient mitigation for the expansion shall be
determined in accordance with ASTM C 1567.
1006- 2.04 Supplementary Cementitious Material ( Fly Ash, Natural
Pozzolan, and Silica Fume)
Fly ash and natural pozzolan shall conform to the requirements of ASTM C 618
for Class C, F, or N mineral admixture, except that the loss on ignition shall not
exceed 3.0 percent.
When a supplementary cementitious material with a calcium oxide content greater
than 15 percent is used, or when the Special Provisions specify sulfate resistant
concrete, the cement intended to be used shall be tested for sulfate expansion in
accordance with ASTM C 1157 and ASTM C 1012. For moderate sulfate
resistance, the maximum expansion shall be 0.10 percent at six months. For high
sulfate resistance, the maximum expansion shall be 0.05 percent at six months and
0.10 percent at one year.
When Class C fly ash is used, the cement intended to be used shall be tested for
sulfate expansion in accordance with ASTM C 1157 and ASTM C 1012 and shall
have a maximum expansion of 0.05 percent at six months and 0.10 percent at one
year.
The use of a supplementary cementitious material is not allowed for replacement
of cement when Portland- pozzolan cement [ Type IP ( MS)] is used. A maximum
of 25 percent of the required weight of Portland cement may be replaced with fly
ash or natural pozzolan [ at 1: 1 replacement ratio]. If performance enhancement
of the concrete, such as the mitigation of an alkali silica reaction or for increased
sulfate resistance is necessary, additional quantities of fly ash or natural pozzolan
may be incorporated into the concrete without a corresponding Portland cement
replacement, if approved by the Engineer.
18
Comments on Arizona Specifications
ADOT is addressing the potential for ASR in a number of ways, as discussed
below in the same order as presented in the specification:
• Cement alkalinity is limited to 0.60 percent Na2Oeq. Further, there is
allowance for the use of blended Portland- pozzolan cement ( ASTM C 595
Type IP ( MS)) which would likely be effective at mitigating ASR.
• The addition of aggregate testing using ASTM C1260 ( 14- day expansion
limit of 0.10 percent) with the requirement to mitigate using ASTM C1567
is a good step in screening aggregates.
• The significantly expanded section on supplementary cementitious materials
( SCMs) allows for a much broader category of materials to be considered,
but few limits are placed. Most of the additions are directed at sulfate
attack, which is discussed in the next chapter. A maximum allowable
replacement of Portland cement of 25 percent does not ensure mitigation,
but there is provision for additional use of SCMs if mitigation is sought.
ASR Specifications in Surrounding States
State Department of Transportation concrete specifications were reviewed from
California, Colorado, Nevada, New Mexico, Texas, and Utah. The results with
regards to ASR and sulfate attack are summarized in the appendix. Table 3
provides a brief summary of how each state addresses ASR. Below is a brief
review of these specifications.
Cement
Most states approach specifying cement in a similar fashion, allowing the use of
ASTM C150, C595, and in some cases, ASTM C1157 cements. Almost all limit
the cements to low alkali, meaning < 0.60 percent Na2Oeq. Some also have lists
of pre- approved or pre- qualified cements. Some require the use of sulfate-resistant
cements as discussed in the next chapter. Several agencies specify the
use of blended cements to address ASR as well as sulfate attack issues.
Aggregate
The most common test employed by the various DOTs for assessing the ASR
susceptibility of aggregates is ASTM C1260, with some requiring ASTM C1293
if a source fails ASTM C1260. All but Caltrans set the expansion limit at 0.10
percent at 14 days ( Caltrans has set a limit of 0.15 percent at 14 days. Several
states apparently have tested local aggregate sources, identified sources of
reactive aggregate, and banned their use.
Water
The primary thrust of the specifications applicable to water used in concrete
mixes is to ensure that it is generally free from contaminants. Several agencies
specifically limit and or test for alkalis.
19
Table 3. Summary of surrounding state concrete specifications related to ASR.
Specification Recommendation
State Cement Water Aggregates SCMs
California
ASTM C150
Type II or
C595 Type IP
< 0.60%
NaOeq
< 300 parts per
million NaOeq.
ASTM C1260
( 0.15@ 14
days)
ASTM C1293
( 0.040@ 1 yr)
Must use admixture to
mitigate ASR. Fly ash,
natural pozzolan, and
silica fume allowed.
Colorado
ASTM C150,
C595, and
C1157 allowed
< 0.90%
NaOeq
“ Reasonably
clean and free
of alkalis.”
ASTM C1260
( 0.10@ 14
days)
CPL 14021
( 0.10@ 14
days)
Fly ash ( Class C and F)
and silica fume allowed.
Must demonstrate the
ability to mitigate.
Nevada
ASTM C150
Types I, III,
and V and
C595
< 0.60%
NaOeq
Water with a
pH < 4.5 or >
8.5 must be
tested.
ASTM C289
Historical
basis.
Require 20 % cement
replacement by fly ash or
natural pozzolan to
mitigate ASR.
New Mexico2
ASTM C150
Type II, C595,
and C1157
allowed
< 0.60%
NaOeq
“ Free of acids
and alkalis.”
ASTM C1260
( 0.10@ 14
days)
ASTM C1293
( 0.40@ 1 yr)
ASTM C1567
( 0.10@ 14
days)
Very comprehensive
allowing Class F fly ash (>
85 % Fe, Si, and Al oxides
and < 8.0 % CaO), slag
cement, silica fume and
blended cements. Also
allows lithium. Must be
tested for effectiveness.
Texas
DMS- 4600
Contribution
of alkalis in
mix from
cement < 4
lb/ yd3 of
concrete
< 600 parts per
million NaOeq.
ASTM C1260
( 0.10@ 14
days)
Many options available.
Allows fly ash, ultra- fine
fly ash, slag cement,
metakaolin, silica fume,
and blends of these.
Lithium is also allowed.
Utah
ASTM C150,
C595, and
C1157
allowed.
< 0.60 %
NaOeq
No specific
ASR
requirements. 3
No specific
ASR
requirements,
but ASTM
C1567 is
limited to
0.10@ 14 days.
Allows fly ash, natural
pozzolans, and silica fume.
Limit CaO < 15 % for fly
ash. Typical 20 %
replacement of fly ash for
cement.
1Colorado Procedure – Laboratory ( CPL) 1402 is a CDOT modified ASTM C1567.
2New Mexico has very comprehensive ASR requirements which are the most thorough of any
state reviewed.
3ASR not specifically addressed yet ASTM C1567 mentioned for mitigation.
Supplementary Cementitious Materials
Many states have detailed guidance in their specifications on the use of
supplementary cementitious materials, either as a replacement for or as an
addition to cement. New Mexico has the most rigorous approach to using SCMs
20
to mitigate ASR, whereas Texas provides for numerous options for blending
various SCMs. A summary of guidance associated with the use of supplementary
cementitious materials includes limiting available alkalis in the mix, specifying
the addition of pozzolans ( 20 to 25 percent minimum), and limiting the CaO
content of the fly ash ( 8 to 15 percent maximum). Although not a supplementary
material, it is noted that some states also allow the use of lithium- based
admixtures to mitigate ASR.
Summary of ASR
Deleterious ( damaging) ASR results from a reaction between the highly alkaline
pore solution in concrete and certain reactive silica constituents in aggregate.
This reaction forms a gel- like reaction product that swells when it imbibes water
and thickens as it reacts with calcium from the paste. The combination of
swelling and thickening creates pressures that are sufficient to fracture the
aggregates and mortar, resulting in cracking and expansion of the structure.
ASR can be effectively prevented by using aggregates that do not contain reactive
constituents. Unfortunately, many aggregates are at least mildly reactive when
tested using ASTM C1260, and thus this strategy is often not an option.
Mitigation strategies include the use of low alkali cements ( e. g., < 0.60 percent
Na2Oeq) and/ or limiting total alkalis in the concrete mix ( e. g., 4.0 lb/ yd3
concrete), although this alone is often not found to be sufficient. The use of
SCMs is thus commonly recommended, with 15 to 25 percent of low CaO fly ash
( commonly classified as Class F) being used as a replacement for or in addition to
cement being the most common mitigation strategy. The use of blends of fly ash,
slag cement, silica fume, and/ or natural pozzolans are also recommended. Some
states also allow the use of lithium- based admixtures as a mitigation strategy.
Testing using ASTM C1567 is often required to assess the effectiveness of the
SCMs in mitigating ASR.
As important as the cement type is, the fact that fly ash is being used in all PCC at
a replacement/ addition rate of 25 to 32 percent has probably played an even larger
role in the generally observed absence of durability problems. For the most part,
these are Class F fly ashes with CaO contents below 6 percent which make them
extremely effective in mitigating ASR. Phoenix Sky Harbor Airport has a lot of
old concrete aprons that were constructed before fly ash was commonly used and
ASR problems are rampant in these pavements. Fly ash has been used on all new
pavements and there are no known ASR problems. It is important to recognize
that fly ash characteristics are always changing due to changes in coal source,
combustor technology, collection methodology, and increasing environmental
demands. Thus there is no assurance that the effectiveness of the fly ash will be
maintained in perpetuity and thus ADOT should consider reviewing their
specifications to ensure future performance.
21
CHAPTER 3.
SULFATE ATTACK
Overview of Sulfate Attack
Sulfate attack occurs when sulfate ions attack constituents in the hydrated cement
paste, which is the glue that holds the concrete together. It is a complicated distress
mechanism which may have both physical and chemical mechanisms of attack, and
may be due to internal or external sources of sulfate. Unless the source of sulfate is
from the aggregate, the role of the aggregate in the occurrence of this distress is
negligible.
In Arizona, the most common type of sulfate attack is caused by an external source of
sulfate ions ( e. g., naturally occurring sulfates of sodium, potassium, calcium, or
magnesium that are found in soil or dissolved in groundwater) attacking cast- in- place
concrete. These penetrating sulfate ions will chemically react with aluminum- and
iron- rich cement hydration products. This is known as chemical sulfate attack from
external sources ( CSAES). CSAES is primarily thought to be caused by the
formation of gypsum through the combination of the external sulfate ions and calcium
ions present in hydration products and/ or the formation of ettringite through the
combination of external sulfate ions and hydrated calcium aluminate phases ( DePuy
1994, ACI 2008). In either case, the formation of the deleterious reaction product
leads to an increase in solid volume. In the former case, expansion due to gypsum
formation may not be destructive, but gypsum has little cementing properties and thus
the concrete loses integrity ( DePuy 1994). In the case of the latter reaction, the
expansive pressures exerted by ettringite formation can be very destructive. In
concrete pavements, deterioration due to external sulfate attack initially appears as
cracking near joints and slab edges, generally within a few years of construction.
Fine longitudinal cracking may also occur parallel to longitudinal joints ( Van Dam et
al. 2002).
A physical form of sulfate attack, known as physical salt attack ( PSA) or salt
weathering, can result from naturally occurring salts of sodium, including sodium
sulfate ( Haynes et al. 2008). First noted in stone monuments, physical salt attack can
lead to surface scaling in concrete just above the ground surface at the evaporative
front. In the research conducted by Haynes et al. ( 2008), temperature and humidity
conditions that promoted alternate cycles of conversion between thenardite ( Na2SO4)
and mirabilite ( Na2SO4 · 10H2O) led to significant scaling. It was found that the
formation of the mirabilite crystals was responsible for most of the scaling damage.
Although indications of chemical sulfate attack were observed, including both
ettringite and gypsum deposits, the damage was attributed almost exclusively to
physical salt attack. It is noted that an ASTM C150 Type II, low calcium aluminate,
moderately sulfate resistant cement was used in this study, along with a very high
water- to- cementitious material ratio ( w/ cm) of 0.65.
22
A third type of sulfate attack is not commonly associated with pavements, but has
been known to occur in mass concrete placements and precast/ steam- cured structural
elements ( Thomas et al. 2008B). The source of the sulfate ions is internal and thus it
is known as internal sulfate attack ( ISA). Internal sources of sulfate ions include
slowly soluble sulfate contained in the cement, aggregate, and admixtures ( such as fly
ash) or those that result from decomposition of primary ettringite during early
hydration. The latter is primarily associated with high curing temperatures, and is
known as delayed ettringite formation ( DEF).
DEF can lead to destructive expansion within the paste, resulting in microcracking
and separation of the paste from aggregate particles. DEF is most often associated
with steam curing. At elevated temperatures ( above 70° C), primary ettringite will not
form properly ( Scrivener 1996, Thaulow et al. 1996, Klemm and Miller 1999). After
the concrete has cured and temperatures are reduced to ambient conditions, sulfates
and aluminate phases in the paste may then react to form expansive ettringite,
disrupting the concrete matrix. Recent work has confirmed that this phenomenon can
also occur in mass placement of cast- in- place concrete that experienced sufficiently
high temperatures due to ambient conditions and the heat generated through cement
hydration ( Thomas et al. 2008b).
Sulfate Attack Test Methods
There are no currently accepted standardized test methods that can be used to test the
sulfate attack resistance of job- mix concrete. Further, testing does not separate
CSAES, PSA, and DEF, primarily focusing on CSAES since it has been the focal
point of concern until fairly recently. The testing that is done focuses exclusively on
the cementitious binder.
DePuy ( 1994) reports that using a cement low in C3A will generally decrease sulfate
attack susceptibility, but exceptions exist where low C3A cements show poor
resistance to sulfate attack while some cements high in C3A were observed to have
good sulfate resistance. He recommends that performance testing using ASTM C 452
and C 1012 should be considered to examine the sulfate resistance of Portland
cements and combinations of cements and SCMs including fly ash and slag,
respectively. In ASTM C 452, mortar bars are made with Portland cement and
gypsum in such proportions that the SO3 content is 7 percent by mass. After mixing
and casting, the mortar bars are cured under very controlled conditions. The initial
length measurement is made at 24 hours, and the specimen is then water cured at 73oF
( 23oC). A second measurement is made at 14 days, and the change in length is
reported. The test can be extended for longer periods of time. The maximum
allowable expansion for ASTM C 150 Type V cement is 0.040 percent at 14 days.
In ASTM C 1012( Length Charge of Hydraulic Cement Mortars Exposed to a Sulfate
Solution), mortar bars are prepared and immersed in a sulfate solution, and the
resulting expansion measured. The cementitious material used can be Portland
cement, or blends of Portland cement and fly ash or slags, or blended hydraulic
cements. The mortar bars are immersed in the sulfate solution after attaining a
23
compressive strength of 20 MPa. A standard exposure solution containing Na2SO4
can be used, or another sulfate solution simulating anticipated field conditions might
be substituted. Length measurements are made at 1, 2, 3, 4, 8, 13, and 15 weeks, and
at selected intervals thereafter depending on the observed rate of length change. The
allowable expansion at 180 days is 0.10 percent for ASTM C595 cements.
Sulfate Attack Mitigation
Guidance is provided for mitigation of sulfate attack through a combination of the use
of a low w/ cm and certain cement types and SCMs ( ACI 2008). Exposure is
classified according to Class 0 through Class 3 based on the percent by mass water-soluble
sulfate ( SO4) in the soil or as sulfate concentration in water in parts per
million. As the concentration of sulfates increases and the exposure severity becomes
more severe, the w/ cm is reduced to limit the permeability of the concrete, thus
hindering the ingress of the aggressive sulfate ions. In the most severe cases ( Class
3), the maximum recommended w/ cm is 0.40 ( ACI 2008).
With regards to the recommendations on cementitious materials, ASTM C150
( AASHTO M 85) Type II ( moderate sulfate resistant) and Type V ( high sulfate
resistant) are the two Portland cements that have some resistance to sulfate attack.
Resistance is obtained by limiting the tricalcium aluminate content calculated from
the oxide analysis to 8 percent and 5 percent for Type II and Type V cement,
respectively. Type V cement also has a further restriction on the combination of all
aluminate and ferrite phases. The purpose of these specifications is to limit the
calcium aluminate hydration products that will form, thus minimizing the phases
present to react with an external source of sulfate ions ( ACI 2008). For a moderate
sulfate environment ( Class 1 exposure), the use of an ASTM C150 Type II cement or
equivalent is recommended. As the severity of the sulfate environment increases,
ASTM C150 Type V cement or equivalent is recommended for a Class 2 exposure
and Type V with pozzolan or slag cement or equivalent is recommended for Class 3
exposure.
The need for high quality, impermeable concrete is a prerequisite for concrete
resistance to external sulfate attack. Concrete with a low w/ cm is consistently
recommended, as it will have lower permeability and thus limit the amount of sulfate
ions that can diffuse into the concrete to attack it. In addition, good workmanship and
curing are essential. It is thought that air entrainment is beneficial only in that it
makes the concrete more workable, so the w/ cm ratio can be reduced. It is also
commonly cited that the use of SCMs will reduce the permeability of concrete and
thus improve the concrete’s resistance to sulfate attack ( ACI 2008).
Class F fly ash is generally found to be beneficial to sulfate resistance, whereas Class
C fly ash may actually be detrimental. For these reasons, only high quality, Class F
fly ash should be considered for use in improving sulfate resistance of concrete. It is
thought that fly ash meeting ASTM C 618 and having less than 10 percent bulk CaO
can be used to improve sulfate resistance. Fly ash containing 10 to 25 percent CaO
should be tested with the actual materials to be used in the concrete.
24
The replacement of Portland cement with slag cement also has beneficial effects
toward sulfate resistance through the reduction of the tricalcium aluminate content
incurred by reducing the amount of Portland cement in the concrete. Slag cement
will also reduce soluble calcium hydroxide, altering the environment required for the
formation of ettringite, and will form additional calcium silicate hydrate in pore
spaces normally occupied by alkalies and calcium hydroxide, reducing the
permeability of the paste.
The sulfate resistance of concrete is decreased through the addition of calcium
chloride, which is a common accelerating admixture. It therefore should not be added
to concrete subjected to sulfate exposure conditions unless Type V cement is used
( ACI 2008).
Due to variability in the effectiveness of various techniques to improve sulfate
resistance, it is important that specific combinations of the cement and pozzolan be
tested to verify sulfate resistance. ASTM C 1012 can be used to assess the sulfate
resistance of blended cements or cement- pozzolan mixtures.
Unfortunately, assessing the sulfate resistance of concrete is difficult. There is
currently no standard ASTM test for assessing the sulfate resistance of specified
concrete made using the selected constituent materials and job mix formula. ASTM
C 452 evaluates only the sulfate resistance of Portland cement and not that of the
concrete. ASTM C 1012 is the most commonly recommended test to assess the
sulfate resistance of Portland cement, blends of Portland cement with slags and fly
ash, or blended hydraulic cements. Six- month expansion limits of 0.10 and 0.05
percent roughly translate to Class 1 exposure resistance and Class 2 exposure
resistance, respectively. It is recommended that one year expansion tests, limiting
expansion to 0.10 percent, are needed to qualify new sources of SCMs for Class 2
exposure. For Class 3 exposure, the test duration is extended to 18 months with an
expansion limit of 0.10 percent.
Sulfate Attack in Arizona
Discussion with representatives of the concrete industry and public agency personnel
indicates a great concern regarding sulfate attack in Arizona. This concern is
validated through a review of USDA Natural Resources Conservation Service records
( USDA 2008), which indicates that the potential for concrete corrosion ( soil- induced
corrosion or weakening of concrete due to sulfate and sodium content of soil) is
widespread throughout the state. Specific soil reports for the State can be found on
the USDA Natural Resources Conservation Service’s web site. As summarized in
table 4, this review indicates that approximately 14 percent of the almost 48,000,000
acres of land area surveyed in Arizona was either moderately or highly corrosive to
concrete. Unfortunately, how the severity levels are defined is not evident in this
data, but it still gives a clear indication that sulfate attack concerns exist in Arizona.
25
Table 4. Summary of risk of concrete corrosion ( USDA 2008).
Percent of Surface Area
Area of Interest
Low Moderate High N/ A
Aguila- Carefree Area, Arizona, Parts of Maricopa and Pinal Counties 95.7% 3.0% 0.0% 1.2%
Apache County, Arizona, Central Part 68.4% 8.8% 3.1% 19.7%
Beaver Creek Area, Arizona 78.1% 0.0% 0.0% 21.9%
Cochise County, Arizona, Douglas- Tombstone Part 51.3% 36.8% 9.7% 2.2%
Cochise County, Arizona, Northwestern Part 50.0% 39.9% 8.9% 1.2%
Coconino County Area, Arizona, Central Part 97.9% 0.0% 1.4% 0.7%
Coconino County Area, Arizona, North Kaibab Part 81.4% 0.0% 5.3% 13.3%
Colorado River Indian Reservation, Parts of La Paz County, Arizona, and Riverside and San Bernardino
Counties, CA 80.8% 16.0% 1.7% 1.4%
Eastern Maricopa and Northern Pinal Counties Area, Arizona 88.7% 0.0% 0.0% 11.3%
Fort Apache Indian Reservation, Arizona, Parts of Apache, Gila, and Navajo Counties 64.7% 35.2% 0.0% 0.1%
Fort Defiance Area, Parts of Apache and Navajo Counties, Arizona and McKinley and San Juan Counties,
New Mexico 93.7% 1.3% 0.2% 4.9%
Gila Bend- Ajo Area, Arizona, Parts of Maricopa and Pima Counties 94.3% 0.2% 3.4% 2.1%
Gila- Duncan Area, Parts of Graham and Greenlee Counties, Arizona 90.8% 0.8% 0.0% 8.4%
Gila River Indian Reservation, Arizona, Parts of Maricopa and Pinal Counties 41.6% 5.0% 53.3% 0.0%
Grand Canyon Area, Arizona, Parts of Coconino and Mohave Counties 33.5% 0.3% 0.2% 66.0%
Hopi Area, Arizona, Parts of Coconino and Navajo Counties 71.0% 13.1% 0.1% 15.8%
Hualapai- Havasupai Area, Arizona, Parts of Coconino, Mohave, and Yavapai Counties 76.3% 0.0% 0.0% 23.7%
Long Valley Area, Arizona 0.2% 0.0% 0.0% 99.8%
Luke Air Force Range, Arizona, Parts of Maricopa, Pima and Yuma Counties 69.7% 2.0% 0.0% 28.3%
Maricopa County, Arizona, Central Part 88.1% 1.4% 8.6% 1.9%
Mohave County Area, Arizona, Northeastern Part, and Part of Coconino County 81.2% 0.4% 15.0% 3.4%
Mohave County, Arizona, Central Part 92.9% 1.2% 0.7% 5.2%
Mohave County, Arizona, Southern Part 94.9% 0.0% 0.1% 5.0%
Navajo County Area, Arizona, Central Part 67.7% 1.1% 19.0% 12.2%
Navajo Mountain Area, Arizona, Parts of Apache, Coconino and Navajo Counties 70.2% 12.7% 0.4% 16.7%
Oak Creek- San Franciso Peaks Area, Arizona, Part of Coconino County 99.2% 0.0% 0.0% 0.8%
Organ Pipe Cactus National Monument, Arizona 100.0% 0.0% 0.0% 0.0%
Pima County, Arizona, Eastern Part 89.0% 9.7% 0.0% 1.3%
Pinal County, Arizona, Western Part 75.1% 9.9% 14.7% 0.3%
Safford Area, Arizona 89.4% 1.3% 1.4% 7.9%
San Simon Area Parts of Cochise Graham and Greenlee Counties, Arizona 75.8% 13.2% 11.1% 0.0%
Santa Cruz and Parts of Cochise and Pima Counties, Arizona 91.9% 0.0% 1.1% 7.0%
Shiprock Area, Parts of San Juan County, New Mexico and Apache County, Arizona 37.4% 24.2% 32.5% 5.9%
Shivwits Area, Arizona, Part of Mohave County 81.2% 7.3% 11.5% 0.0%
Tohono O'Odham Nation, Arizona, Parts of Maricopa, Pima and Pinal Counties 89.9% 2.4% 7.7% 0.0%
Tucson- Avra Valley Area, Arizona 99.7% 0.3% 0.0% 0.0%
Virgin River Area, Nevada and Arizona 57.3% 1.3% 14.4% 27.0%
Willcox Area, Arizona Parts of Cochise and Graham Counties 68.1% 3.8% 20.3% 7.7%
Yavapai County, Arizona, Western Part 85.9% 3.0% 0.0% 11.1%
Yuma- Wellton Area, Parts of Yuma County, Arizona and Imperial County, California 62.2% 2.3% 30.9% 4.6%
Totals 77.4% 6.9% 5.9% 10.0%
26
In the 1950s, cements were designed so that they gave moderate sulfate resistance
as a standard. This was the old ASTM C150 Type II ( modified). They also
produced a Type V cement to be used where there were problems. Today, there is
very little Type V produced, unless a contractor is expecting a problem on a
sizable project. However, Type V is widely used in the concrete pipe industry.
The Phoenix Cement Company started its cement plant in Clarkdale in 1959 in
response to receiving the contract for the cement for the Glen Canyon Dam. At
that time, it started using Type II cement. Later it began making a Type IP with
fly ash ground directly into the cement. It is believed that Type IP is now only
made on special request. The Phoenix Cement Company is now a division of the
Salt River Materials Group and is still manufacturing Type II/ V cement.
Other minor cement producers are Mitsubishi Cement, which owns a small plant
in California that provides cement in Arizona, and the Lehigh Cement Company,
which also owns a small plant in California that produces minimal amounts of
cement used in Arizona. CEMEX is also active in Arizona, with two nearby
plants in Mexico from which it is primarily providing Type II cements to Arizona.
It is noted that cement plants change ownership frequently, especially under the
current economic situation.
Arizona’s sulfate problems are statewide and are not dependent on the aggregates
involved. The available cements are “ moderately sulfate resistant” per ASTM
C150 Type II. This requirement has been important in reducing sulfate attack
problems in most parts of the State. In the Yuma area, along the Colorado River,
the sulfate problem is particularly aggressive and the U. S. Bureau of Reclamation
has mandated the use of Type V cement for the past 50 years or more. The
domestic cements available over the past few years have been blended to create
Type II/ V equivalent cement, and that blend is now being used successfully, both
in that area and in the rest of the State.
The fact that fly ash is being used in all PCC used by ADOT at a replacement/
addition rate of 25 to 32 percent is also extremely important. For the most part,
these are Class F fly ashes with CaO contents below 6 percent which make them
extremely effective in mitigating sulfate attack. Fly ash has been used on all new
pavements and there are no known sulfate attack problems. As noted in the
previous chapter, it is important to recognize that fly ash characteristics are
always changing due to variations in coal source, combustor technology,
collection methodology, and increasing environmental demands. Thus there is no
assurance that the effectiveness of the fly ash will be maintained in perpetuity and
ADOT should review their specifications to ensure future performance.
Sulfate Attack Specifications in Arizona
Section 1006 ( dated February 20, 2007) of the Arizona DOT specifications was
reviewed as it pertains to sulfate attack as well as other durability concerns. The
27
following relevant sections have been extracted from the specifications.
Underlined passages are new since the 2000 edition of the Standard
Specifications.
1006- 2.01 Cement
Hydraulic cement shall consist of either Portland cement or Portland- pozzolan
cement. Portland cement shall conform to the requirements of ASTM C 150 for
Type II, III, or V. However, at the option of the manufacturer, processing
additions may be used in the manufacture of the cement, provided such
processing additions have been shown to meet the requirements of ASTM C 465,
and the total amount of such material used does not exceed one percent of the
weight of the Portland cement clinker.
Portland- pozzolan cement shall conform to the requirements of ASTM C 595 for
Type IP ( MS).
1006- 2.02 Water
The water used shall be free from injurious amounts of oil, acid, alkali, clay,
vegetable matter, silt or other harmful matter. Water shall contain not more than
1,000 ppm of chlorides as Cl and not more than 1,000 ppm of sulfates as SO4.
1006- 2.04 Supplementary Cementitious Material ( Fly Ash, Natural
Pozzolan, and Silica Fume)
Fly ash and natural pozzolan shall conform to the requirements of ASTM C 618
for Class C, F, or N mineral admixture, except that the loss on ignition shall not
exceed 3.0 percent.
When a supplementary cementitious material with a calcium oxide content greater
than 15 percent is used, or when the Special Provisions specify sulfate resistant
concrete, the cement intended to be used shall be tested for sulfate expansion in
accordance with ASTM C 1157 and ASTM C 1012. For moderate sulfate
resistance, the maximum expansion shall be 0.10 percent at six months. For high
sulfate resistance, the maximum expansion shall be 0.05 percent at six months and
0.10 percent at one year.
When Class C fly ash is used, the cement intended to be used shall be tested for
sulfate expansion in accordance with ASTM C 1157 and ASTM C 1012 and shall
have a maximum expansion of 0.05 percent at six months and 0.10 percent at one
year.
The use of a supplementary cementitious material is not allowed for replacement
of cement when Portland- pozzolan cement [ Type IP ( MS)] is used. A maximum
of 25 percent of the required weight of Portland cement may be replaced with fly
ash or natural pozzolan [ at 1: 1 replacement ratio]. If performance enhancement
of the concrete, such as the mitigation of an alkali silica reaction or for increased
sulfate resistance is necessary, additional quantities of fly ash or natural pozzolan
28
may be incorporated into the concrete without a corresponding Portland cement
replacement, if approved by the Engineer.
1006- 3.01 Water- to- Cement Ratio ( w/ cm)
For Class P Concrete, no w/ cm is specified.
Comments on Arizona Specifications
ADOT is addressing the potential for sulfate attack in a number of ways, as
discussed below in the same order as presented in the specification:
• Cement type is specified as either Type II or V, although Type III2 is also al-lowed.
Further, there is allowance for the use of blended Portland- pozzolan
cement ( ASTM C 595 Type IP ( MS)) which would likely be effective at
mitigating sulfate attack.
• The sulfate content in the mixing water is limited to not more than 1,000
ppm of sulfates as SO4.
• The significantly expanded section on supplementary cementitious materials
( SCMs) allows a much broader category of materials to be considered, but
few limits are placed. Sulfate attack is addressed by testing cement/ SCM
blends through use of ASTM C1012, applying expansion limits of 0.10 per-cent
at 6 months for moderate sulfate resistance and 0.05 percent at 6 months
and 0.10 percent at 1 year for high sulfate resistance. Since the maximum
allowable replacement of Portland cement of 25 percent does not ensure
resistance to sulfate attack, there is provision for additional use of SCMs if
mitigation is sought.
Sulfate Attack Specifications in Surrounding States
Concrete specifications were reviewed from Departments of Transportation in
California, Colorado, Nevada, New Mexico, Texas, and Utah. The results are
summarized in the appendix. Table 5 provides a brief summary of how each state
addresses sulfate. Below is a brief review of those specifications.
Cement
Most states approach specifying cement in a similar fashion, allowing the use of
ASTM C150, C595, and in some cases, ASTM C1157 cements. Almost all
require that Type II or V cement be used if sulfate attack is of concern. Texas has
very specific requirements for mitigating sulfate attack. Some also have lists of
pre- approved or pre- qualified cements. Several agencies specify the use of
blended cements to address ASR as well as sulfate attack issues.
2 Note that the ASTM C150 specification for Type III makes and allowance for moderate sulfate
resistance if the C3A content is less than 8 percent.
29
Water
The primary thrust of the specifications applicable to water used in concrete mixes
is to ensure that it is generally free from contaminants. Several agencies specific-ally
limit and or test for sulfates with the limits being set at 1,000 to 3,000 ppm.
Table 5. Summary of surrounding state concrete specifications as pertains to sulfate attack.
Specification Recommendation
State Cement w/ cm Water SCMs
California ASTM C150 Type II or V
or C595 Type IP. Mortar
shall not expand more than
0.010 when tested in
conformance with
California Test 527.
Not specified.
Water content is
controlled
primarily based
on workability.
< 1,300 ppm of
sulfates as SO4,
when tested in
conformance
with California
Test 417.
Fly ash, natural pozzolans,
and silica fume are allowed.
Use focuses on ASR, not
sulfate attack, but amount
varies depending on CaO
content in fly ash.
Colorado ASTM C150, C595, and
C1157 allowed.
< 0.44 – Not
related to sulfate
resistance.
No specific
mention of
sulfate.
Fly ash ( Class C and F) and
silica fume allowed. Must
demonstrate the ability of fly
ash to mitigate sulfate attack
through use of ASTM
C1012.
Nevada ASTM C150 Type V is to
be used when sulfate
protection is required.
< 0.47 – Not
related to sulfate
resistance.
No specific
mention of
sulfate.
Replacement of cement by
fly ash or natural pozzolan
only specified to mitigate
ASR.
New Mexico ASTM C150 Type II,
C595, and C1157 allowed
Not specified. < 1,000 ppm of
sulfates as SO4
Very comprehensive
specifications for using fly
ash, slag cement, silica fume,
or blended cement. Class C
fly ash cannot be used in
sulfate- resistant concrete
Texas Detailed guidance to
mitigate sulfate attack
using Type I/ II, II, V, IP,
or IS cement.
< 0.45 – Not
related to sulfate
resistance.
Sulfate content
in accordance
with ASTM
D516 < 1,000
ppm.
Class C fly ash not allowed
in sulfate- resistant concrete.
Combinations of Class F fly
ash, slag cement, and silica
fume allowed.
Utah ASTM C150 Type II,
C595, and C1157 allowed.
< 0.44 – Not
related to sulfate
resistance.
< 3,000 ppm of
sulfates as SO4.
Allows fly ash, natural
pozzolans, and silica fume.
Limit CaO < 15% for fly ash.
Typical 20% replacement of
fly ash for cement.
30
Supplementary Cementitious Materials
Many states have detailed guidance in their specifications related to the use of
supplementary cementitious materials, either as a replacement for or as an
addition to cement. New Mexico has the most rigorous approach to using SCMs
to mitigate ASR, but this approach would also be effective in mitigating sulfate
attack. Texas forbids the use of Class C fly ash in sulfate- resistant concrete and
provides for numerous options for blending various SCMs. A summary of
guidance associated with the use of supplementary cementitious materials for
addressing sulfate attack includes specifying the addition of pozzolans ( 20 to 25
percent minimum), limiting the CaO content of the fly ash ( 8 to 15 percent
maximum), and the use of ASTM C1012 expansion testing.
Water- to- Cementitious Material Ratio ( w/ cm)
In no case was the w/ cm limit established to specifically address sulfate attack.
Most states set limits ( from 0.44 to 0.47), but two did not. The main concern in
establishing w/ cm was primarily to achieve strength, but permeability
requirements were also considered. The latter has a direct bearing on sulfate
attack resistance.
Summary of Sulfate Attack
Deleterious ( damaging) sulfate attack most commonly occurs due to the ingress of
external sulfate ions from soils ( e. g., naturally occurring sulfates of sodium,
potassium, calcium, or magnesium that are found in soil or dissolved in
groundwater). These ions will react with normal cement hydration products to
form ettringite and/ or gypsum. In the former case, expansion of the paste results
in cracking and degradation and in the latter, the paste loses strength and becomes
soluble. A purely physical mechanism, commonly referred to as physical salt
attack or salt weather, can also cause concrete degradation as a result of sulfate
salts present in the soil being wicked up to the surface and then evaporating just
above the ground level. This causes salt crystallization and scaling of the
concrete at the surface.
Concrete can be made resistant to sulfate attack by limiting its permeability and/ or
limiting the hydration products that react with the sulfates. Permeability is most
directly influenced by the w/ cm, with limits of 0.45 or below recommended to
assist in preventing ingress of external sulfate ions ( ACI 2008). The use of
pozzolans ( e. g., low CaO fly ash, silica fume, and so on) or slag cement has also
been shown to be very effective in reducing the permeability of concrete and are
thus often recommended to increase concrete’s resistance to sulfate attack. The
two hydration products most directly affected by sulfate attack are phases
containing aluminum and calcium hydroxide. Limits on the calculated tricalcium
aluminate content of the cement are the basis for improving cement resistance to
sulfate attack ( e. g., Types II and V Portland cement). Calcium hydroxide is often
limited through the addition of pozzolans or slag cement.
31
Guidance to mitigate sulfate attack is provided by ACI ( 2008). The severity of
the sulfate environment is assessed based on determining the water soluble sulfate
ion concentration present in the soil, but it is recognized that many factors
contribute to the aggressiveness of the environment. For example, all things
equal, soils containing calcium sulfate are less aggressive than those containing
sodium sulfate, which again are less aggressive than those containing magnesium
sulfate. Depending on the severity of the environment, the guidelines recommend
reducing the w/ cm and the use of sulfate resistant cements.
In Arizona, in addition to the cement type, the fact that high quality Class F fly
ash is being used in all PCC at a replacement/ addition rate of 25 to 32 percent
plays a large role in controlling sulfate attack. For the most part, these fly ashes
have CaO contents below 6 percent which make them extremely effective in
mitigating sulfate attack. Fly ash has been used on all new pavements and there
are no known sulfate attack problems. It is important to recognize that fly ash
characteristics are always changing due to changes in coal source, combustor
technology, collection methodology, and increasing environmental demands.
Thus there is no assurance that the effectiveness of the fly ash will be maintained
in perpetuity and thus ADOT should review their specifications to ensure future
performance.
32
33
CHAPTER 4.
SUMMARY OF FINDINGS
AND RECOMMENDATIONS
The findings of this study can be summarized as follows:
• Both ASR and sulfate attack can potentially impact concrete transportation
structures in Arizona, although little evidence exists that links either
mechanism to degradation in newly constructed pavements or bridges.
• In particular, there is little immediate concern over ASR, although it is
known that reactive aggregates can be found over a broad geographic area
including in the vicinity of the Salt River ( and possibly the Gila River as
well) and along the Santa Cruz River. ADOT has likely avoided obvious
ASR problems due to routine use of relatively low alkali cement ( 0.60
percent Na2Oeq) and the use of low CaO content Class F fly ash ( at 25 to
32 percent replacement for cement). ADOT also has allowance for the use
of blended Portland- pozzolan cement ( ASTM C 595 Type IP ( MS)) which
would also likely be effective at mitigating ASR.
• The addition of aggregate screening testing to the ADOT specification
through the use of ASTM C1260 ( 14- day expansion limit of 0.10 percent)
is a good step in identifying susceptible aggregates. Mitigation of
potentially reactive aggregates follows the current state- of- the- practice of
requiring testing using ASTM C1567, in which the cementitious system is
a blend of the Portland cement and SCM( s) to be used in the job mix.
• Although ADOT now requires aggregate screening, many of the surrounding
states have more detailed guidance in their specifications related to the use
of supplementary cementitious materials, either as a replacement for or as
an addition to Portland cement. New Mexico has the most rigorous
approach to mitigate ASR using SCMs, whereas Texas provides numerous
options for blending various SCMs. Guidance associated with the use of
SCMs includes limiting available alkalis in the mix, specifying the
addition of pozzolans ( 20 to 25 percent minimum), and limiting the CaO
content of the fly ash ( 8 to 15 percent maximum). Although not a
supplementary material, it is noted that some states also allow the use of
lithium- based admixtures to mitigate ASR.
• The potential for sulfate attack exists over a wide geographical area, with 6.9
and 5.9 percent of the surface area of Arizona considered as having
moderate to high potential for concrete corrosion ( including sulfate
attack), respectively. ADOT specifies either Type II or V cements, which
34
have moderate or high resistance to sulfate attack, respectively. Further,
there is allowance for the use of blended Portland- pozzolan cement
( ASTM C 595 Type IP ( MS)) which would likely be effective at
mitigating sulfate attack.
• The significantly expanded section in the ADOT specifications on supple-mentary
cementitious materials ( SCMs) allows a much broader category
of materials to be considered, but few limits are placed. Sulfate attack is
addressed by testing cement/ SCM blends through use of ASTM C1012,
applying expansion limits of 0.10 percent at 6 months for moderate sulfate
resistance and 0.05 percent at 6 months and 0.10 percent at 1 year for high
sulfate resistance. Since the maximum allowable replacement of Portland
cement with an SCM is 25 percent, resistance to sulfate attack is not
ensured, but there is provision for the use of additional SCMs if mitigation
is sought.
• ADOT’s approach to mitigating sulfate attack is consistent with that of most
surrounding states which also specify the use of Type II and V cements.
Further, guidance associated with the use of supplementary cementitious
materials for addressing sulfate attack includes specifying the addition of
pozzolans ( 20 to 25 percent minimum), limiting the CaO content of the fly
ash ( 8 to 15 percent maximum), and the use of ASTM C1012 expansion
testing.
Based on this study, ADOT’s current practices are consistent with that of its
neighbors, but by no means are they the most rigorous, particularly related to
controlling ASR. The following recommendations are made to improve ADOT’s
approach to ASR and sulfate attack mitigation to ensure success in the future:
• Although ADOT has benefited from abundant sources of low CaO Class F
fly ash, it is important to recognize that fly ash characteristics are
changing as the coal source, combustor technology, collection
methodology, and increasing environmental demands change. Thus there
is no assurance that the effectiveness of the fly ash ADOT is currently
using will be maintained in perpetuity. ADOT should review their SCM
specifications to ensure that those materials being used in their concrete
have the desired effect of mitigating ASR and sulfate attack. Of the
specifications reviewed, those currently employed by New Mexico are the
most thorough.
• For the most part, ADOT’s specifications for cement are similar to those of
the surrounding states with one exception: a number of neighboring states
also permit the use of ASTM C1157 performance specified cements.
ADOT should investigate allowing the use of these cements as well.
35
• With regards to aggregate screening for ASR, ADOT is following the current
state- of- the- practice utilizing accelerated mortar bar testing in compliance
with ASTM C1260/ C1567. This test has some limitations, but its short
duration ( 16 days from casting to completion) makes it extremely
attractive for project use. The new FHWA guidelines ( Thomas et al.
2008A) recommend that long- term concrete prism testing be conducted in
accordance with ASTM C1293 to establish an empirical relationship with
the ASTM C1260 test results to ensure mitigation. This would require
ADOT to embark on a long- term study to test its most common ASR-susceptible
aggregates, but it is the only currently acceptable approach to
establishing confidence that the ASTM C1260/ C1567 results accurately
predict field performance.
36
37
REFERENCES
ACI. 2008. Guide to Durable Concrete. ACI 201.2R- 08. Farmington Hills, MI:
American Concrete Institute.
Air Force. 2006. Engineering Technical Letter ( ETL) 06- 2: Alkali- Aggregate
Reaction in Portland Cement Concrete ( PCC) Airfield Pavements. Tyndale AFB.
FL: Department of the Air Force. Headquarters Air Force Civil Engineer Support
Agency.
Arizona Department of Transportation. 2000. Standard Specifications for Road
and Bridge Construction. Phoenix, AZ: ADOT.
Bérubé, M.- A. and B. Fournier. 1992. “ Effectiveness of the Accelerated Mortar
Bar Method, ASTM C9 Proposal P214 or NBRI for Assessing Potential AAR in
Quebec ( Canada).” Proceedings of the Ninth International Conference on Alkali-
Aggregate Reaction in Concrete. Slough, UK: Concrete Society. pp. 92- 101.
DePuy, G. W. 1994. “ Chemical Resistance of Concrete.” Significance of Tests
and Properties of Concrete and Concrete- Making Materials. STP 169C.
Philadelphia, PA: American Society for Testing and Materials. pp. 263- 281.
Diamond, S. 1989. " ASR— Another Look at Mechanisms." Proceedings of the 8th
International Conference on Alkali- Aggregate Reaction. ( Ed. K. Okada, S.
Nishibayashi, and M. Kawamura), Kyoto, Japan. London, UK: Spon Press. pp.
83- 94.
Farny, A. J. and B. Kerkhoff. 2007. Diagnosis and Control of Alkali- Aggregate
Reactions in Concrete. IS413. Skokie, IL: Portland Cement Association. 25 p.
Folliard, K. J., M. D. A. Thomas and K. E. Kurtis. 2003. Guidelines for the Use of
Lithium to Mitigate or Prevent ASR. FHWA- RD- 03- 047. McLean, VA: Federal
Highway Administration.
Folliard, K. J., R. Barborak, T. Drimalas, L. Du, S. Garber, J. Ideker, T. Ley, S.
Williams, M. Juenger, M. D. A. Thomas and B. Fournier. 2006. Project 0- 4085:
Preventing Premature Concrete Deterioration Due to ASR/ DEF in New Concrete.
Final Report. Austin, TX: Center for Transportation Research. University of
Texas at Austin. Work conducted for the Texas Department of Transportation.
Hansen, W. C. 1944. " Studies Relating to the Mechanism by which the Alkali-
Aggregate Reaction Produces Expansion in Concrete." Journal of the American
Concrete Institute 15( 3): 213- 227.
38
Haynes, H., R. O’Neill, M. Neff, and P. K. Mehta. 2008. “ Salt Weathering
Distress on Concrete Exposed to Sodium Sulfate Environment.” ACI Materials
Journal 105( 1): 35- 43.
Ichikawa, T. and M. Miura. 2007. “ A Modified Model of Alkali Silica Reaction.”
Cement and Concrete Research 37( 9): 1291- 1297.
Klemm, W. and F. M. Miller. 1999. “ Internal Sulfate Attack: Distress Mechanism
at Ambient and Elevated Temperatures?” Ettringite – The Sometimes Host of
Destruction. SP- 177. Farmington Hills, MI: American Concrete Institute. pp. 81-
92.
Lindsey, D. A.
and R. Melick. undated. Reconnaissance of Alluvial Fans as
Potential Sources of Gravel Aggregate, Santa Cruz River Valley, Southeast
Arizona. Open File Report 02- 314. United States Geologic Survey.
Malvar, L. J., L. Lenke and G. Cline. 2008. Use of Fly Ash in DOD Airfield
Concrete Pavements. Presentation at Workshop at the 9th International
Conference on Concrete Pavements. San Francisco, CA. Aug. 17- 21.
Malvar, L. J. and L. Lenke. 2008. ASR Potential: C 1260 Thresholds and C 1293.
Presentation given at the Tri- Service Pavement Committee Meeting, Atlanta, GA,
Dec. 3.
McGowan, J. K. and H. E. Vivian. 1952. " Studies in Cement- Aggregate Reaction:
Correlation between Crack Development and Expansion of Mortars." Australian
Journal of Applied Science 3: 228- 232.
Powers, T. C. and H. H. Steinour. 1955. " An Interpretation of Some Published
Researches on Alkali- Aggregate Reaction. I: The Chemical Reactions and
Mechanism of Expansion." Journal of the American Concrete Institute 26( 6):
497- 516.
Rogers, C. A., and R. D. Hooton. 1991. “ Reduction in Mortar and Concrete
Expansion with Reactive Aggregates Due to Alkali Leaching.” Cement, Concrete,
and Aggregates. Vol. 13, No. 1. American Society for Testing and Materials. pp.
42- 49.
Scrivener, K. L. 1996. “ Delayed Ettringite Formation and Concrete Railroad
Ties.” Proceedings: 18th International Conference on Cement Microscopy.
Houston, TX. April 21- 25. pp. 375- 377.
Stokes, D. 2006. “ Concerning the Use of Expansion Data from ASR Testing”.
Proceedings of the 8th CANMET/ ACI International Conference on Recent
Advances in Concrete Technology. Marc- Andre Berube Symposium. Montreal
Canada. May- June. Pp. 93- 109.
39
Thaulow, N., V. Johansen and U. H. Jakobsen. 1996. What Causes Delayed
Ettringite Formation? Bulletin No. 60. Presented at the Fall 1995 Meeting of
MRS in Boston. Idorn Consult A/ S, Denmark. March. 12 pp.
Thomas, M. D. A, B. Fournier and K. Folliard. 2008A. Report on Determining the
Reactivity of Concrete Aggregates and Selecting Appropriate Measures for
Preventing Deleterious Expansion in New Construction. FHWA- HIF- 09- 001.
Washington, DC: Federal Highway Administration.
Thomas, M. D. A., K. Folliard, T. Drimalas and T. Ramlochan. 2008B.
“ Diagnosing Delayed Ettringite Formation in Concrete Structures.” Cement and
Concrete Research 38( 6): 841- 847.
United States Department of Agriculture ( USDA). 2008. Web Soil Survey 2.0 –
National Cooperative Soil Survey. Natural Resources Conservation Service.
http:// websoilsurvey. nrcs. usda. gov/ app/ WebSoilSurvey. aspx. Accessed
November 2009.
Van Dam, T. J., L. L. Sutter, K. D. Smith, M. J. Wade and K. R. Peterson. 2002.
Guidelines for Detection, Analysis, and Treatment of Materials- Related Distress
in Concrete Pavements - Volume 1: Final Report. FHWA- RD- 01- 163. McLean,
VA: Federal Highway Administration. Turner- Fairbank Highway Research
Center.
40
41
APPENDIX
SUMMARY OF SPECIFICATIONS USED BY NEIGHBORING
STATES TO AID IN ASR AND SULFATE ATTACK
MITIGATION
California
Imad Basheer
916- 227- 5840
Link to State Specifications Website:
http:// www. dot. ca. gov/ hq/ esc/ oe/ specifications/ std_ specs/ 2006_ StdSpecs/
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland
Cement Concrete ( PCC):
Aggregate
• Aggregates shall have not more than 10 percent loss when tested for
soundness in conformance with the requirements in California Test 214.
• When the aggregate is tested in conformance with the requirements in
California Test 554 and ASTM Designation C 1293, the average
expansion at one year shall be less than or equal to 0.040 percent.
• When the aggregate is tested in conformance with the requirements in
California Test 554 and ASTM Designation C 1260, the average of the
expansion at 16 days shall be less than or equal to 0.15 percent.
Water
• Water shall not contain more than 1,300 parts per million of sulfates as SO4,
when tested in conformance with California Test 417.
• Water shall not contain coloring agents or more than 300 parts per million of
alkalis ( Na2O + 0.658 K2O)
Cement
• “ Type II Modified" Portland cement shall conform to the requirements for
Type II Portland cement in ASTM Designation C 150- 02a.
• " Type IP ( MS) Modified" cement and " Type II Modified" Portland cement
shall conform to the following requirements:
A. The cement shall not contain more than 0.60 percent by weight of
alkalis, calculated as the percentage of Na2O plus 0.658 times the
percentage of K2O, when determined by either direct intensity flame
photometry or by the atomic absorption method. The instrument and
42
procedure used shall be qualified as to precision and accuracy in
conformance with the requirements in ASTM Designation C 114;
B. The autoclave expansion shall not exceed 0.50 percent; and
C. Mortar, containing the cement to be used and Ottawa sand, when
tested in conformance with California Test 527, shall not expand in
water more than 0.010 percent and shall not contract in air more than
0.048 percent, except that when cement is to be used for precast
prestressed concrete piling, precast prestressed concrete members, or
steam cured concrete products, the mortar shall not contract in air
more than 0.053 percent.
Supplementary Cementitious Materials
• The amounts of cement and mineral admixture used in cementitious material
shall be sufficient to satisfy the minimum cementitious material content
requirements specified in Section 90- 1.01, " Description," or Section 90-
4.05, " Optional Use of Chemical Admixtures," of the Standard
Specifications.
• Coal fly ash; raw or calcined natural pozzolan, or silica fume may be used as
mineral admixtures.
• When admixtures are used, the available alkali content ( as sodium oxide
equivalent) shall not exceed 1.5 percent when determined in conformance
with the requirements in ASTM Designation C 311, or the total alkali
content ( as sodium oxide equivalent) shall not exceed 5.0 percent when
determined in conformance with the requirements in ASTM Designation
D 4326.
• Admixture materials shall conform to the requirements in the following
ASTM Designations:
A. Chemical Admixtures— ASTM Designation C 494.
B. Air- entraining Admixtures— ASTM Designation C 260.
C. Calcium Chloride— ASTM Designation D 98.
D. Mineral Admixtures— Coal fly ash; raw or calcined natural
pozzolan as specified in ASTM Designation C 618; silica fume
conforming to the requirements in ASTM Designation C 1240,
with reduction of mortar expansion of 80 percent, minimum, using
the cement from the proposed mix design.
• Unless otherwise specified in the special provisions, mineral admixtures
shall be used in conformance with the provisions in Section 90- 4.08,
" Required Use of Mineral Admixtures.”
43
Colorado
Larry Brinck
larry. brinck@ dot. state. co. us
303- 757- 9474
Link to State Specifications Website:
http:// www. dot. state. co. us/ DesignSupport/ Construction/ 2005SpecsBook/ 2
005index. htm
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland
Cement Concrete ( PCC):
Aggregate
Any aggregate with expansion of 0.10 percent at 16 days as determined by ASTM
C 1260 shall not be used unless mitigative measures are included and subsequent
results of CPL 4202 show an expansion less than 0.10 percent at 16 days. [ Note:
CPL 4202 is a department modified version of ASTM C 1567.]
Coarse Aggregate
Coarse aggregate shall conform to the requirements of AASHTO M 80.
Fine Aggregate
The fine aggregates should meet the requirements of AASHTO M 6.
Water
• Water will be tested in accordance with, and shall meet the suggested
requirements of AASHTO T 26.
• Water used in mixing or curing shall be reasonably clean and free of alkali.
Cement
• Cement shall be from a preapproved source listed on the department’s
Approved Products List.
• Portland cement shall conform to the requirements of ASTM C 150.
• Blended cement shall conform to the requirements of ASTM C 595.
• Hydraulic cement shall conform to the requirements of ASTM C 1157
( Standard Performance Specification for Hydraulic Cement).
• Maximum percent of equivalent alkalis ( Na2O + 0.658 K2O) shall not exceed
0.90 percent.
• Type IP or IP( MS) may be used in place of Type I or II. Blended cement
shall consist of no less than 70 percent Portland cement. Hydraulic
cement according to ASTM C 1157, Type GU or MS may also be used.
44
Supplementary Cementitious Materials
• Fly ash for concrete shall conform to the requirements of ASTM C 618, Class
C or Class F.
• Where Class F fly ash is required, Type IP or IP( MS) cement may be used,
except blended cement shall consist of no less than 70 percent Portland
cement and no less than 20 percent fly ash.
• Fly ash used to enhance sulfate resistance, shall be used in a proportion greater
than or equal to the proportion tested in accordance to ASTM C1012 and it
shall have a calcium oxide content no more than 2.0 percent greater than the
fly ash tested according to ASTM 1012.
• Silica fume for concrete shall conform to the requirements of ASTM C 1240.
Structural Concrete
• The Contractor shall provide protection against sulfate attack on concrete
structures by providing concrete structures manufactured with requirements
according to Table 601- 4. The exposure Class will be stated on the plans.
Table 601- 4— Requirements to protect against damage to concrete by
sulfate attack from external sources of sulfate— provides criteria for severity
of potential exposure ( percent of water soluble sulfate in dry soil, sulfate in
water, water cement ratio) and specifies the type of cement to be used.
• The Concrete Mix Design Report shall state what mitigative measures were
included in the concrete mix design and include results for CPL 4201 and
CPL 4202.
Nevada
Reid Kaiser
Chief Materials Engineer
775- 888- 7000
rkaiser@ dot. state. nv. us
Link to State Specifications Website:
http:// www. nevadadot. com/ business/ contractor/ standards/
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland Cement
Concrete ( PCC):
Aggregate
• Aggregates should be innocuous when tested for ' Potential Reactivity' under
ASTM C289.
• Aggregates from any source having a history of alkali- silica reactivity in
concrete will not be approved for use.
45
Coarse Aggregate
Coarse aggregate shall be tested in accordance with AASHTO T104 and shall
have a 5- cycle sodium sulfate soundness loss of not more than 12 percent.
Fine Aggregate
Fine aggregate shall be tested in accordance with AASHTO T104 and shall have a
5- cycle sodium sulfate soundness loss of not more than 12 percent.
Water
Water with a pH less than 4.5 or greater than 8.5 and a resistivity less than 500
ohm. cm will be tested according to AASHTO T26.
Cement
• Type II, Type III, and Type V Portland cements shall conform to ASTM
C150
• Type IP blended hydraulic cement shall conform to ASTM C595
• The cement shall not contain more than 0.60 percent by mass of alkalies
calculated as Na2O plus 0.658 K2O.
• Type IP cement which exceeds the allowable alkali content may be used if
mortar bars made and tested according to ASTM C227, using the proposed
cement and a selected highly alkali- reactive aggregate, show no more than
0.05 percent expansion at 6 months.
• Type V cement is to be used when sulfate protection is required for concrete
structures
Supplementary Cementitious Materials
• If the proposed aggregate fails the test requirement for “ Potential
Reactivity” under ASTM C289, the aggregate may still be used for
concrete provided that it is incorporated in an approved mix design with
an approved Type F or Type N pozzolan, or with a Type IP cement. If a
pozzolan is used for this purpose, use 1 part pozzolan to 4 parts of cement
by mass. The pozzolan quantity shall be considered as cement in meeting
the required minimum cement content.
• Pozzolan shall conform to Subsection 702.03.05. The pozzolan
constituent shall be limited to a maximum of 20 percent by mass of the
blended cement.
46
New Mexico
John H. Tenison
John. Tenison@ state. nm. us
505- 827- 9811
Link to State Specifications Website:
http:// www. nmshtd. state. nm. us/ main. asp? secid= 11183
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland
Cement Concrete ( PCC):
Aggregate
• The Department’s State Materials Bureau maintains a list of reactive,
potentially reactive, and non- reactive ( innocuous) aggregate sources.
• All aggregates shall be evaluated for reactivity by AASHTO T 303 or by
ASTM C 1293. The initial “ Proof- of- Reactivity- Potential” test will be
performed utilizing a standard Rio Grande Type I- II low alkali cement.
This cement shall have alkali content between 0.5 to 0.6 percent.
Aggregates that exhibit mean mortar bar expansions at 14 days greater
than 0.10 percent shall be considered potentially reactive. Aggregates will
be considered innocuous if their maximum expansion is less than 0.10
percent at 14 days unless ASTM C 1293 is used, then the aggregate shall
be considered to be innocuous if the average expansion measured at the
end of one ( 1) year is less than 0.04 percent.
Coarse Aggregate
Coarse aggregate shall have an Aggregate Index ( A. I.) of 25 or less, when
calculated in accordance with Section 910, “ Aggregate Index.”
Fine Aggregate
Fine aggregate shall have a soundness loss of 12 or less when tested in accordance
with AASHTO T104 using magnesium sulfate solution with a test duration of five
( 5) cycles.
Water
• Water shall be sampled and tested in accordance with AASHTO T 26 and be
free of acid and alkali.
• The sulfate content and the chloride content each shall not exceed 1,000
ppm.
47
Cement
• Portland cement shall be “ low- alkali” and shall meet the requirements of
ASTM C 150 for the type required. Type II cement is required unless
otherwise specified.
• ASTM C595 and C1157 also allowed.
• If the ASR mitigation test required in subsection 509.2.4.5 is less than 0.10
percent for each aggregate, then the requirement for low- alkali shall be
waived.
Supplementary Cementitious Materials
• Minimum 20 percent fly ash in blended cement. Use Class F fly ash if either
aggregate is reactive. Class C fly ash may be used if neither aggregate is
reactive.
• Fly ash shall conform to the physical and chemical requirements of ASTM C
618, including the optional requirements for available alkalis and
reactivity with cement alkalis.
• If the Contractor elects to use an aggregate source which has been designated
as potentially reactive or known reactive, a combination of one or more of
the following ASR inhibiting admixtures, shall be used to provide a
concrete mixture that meets the maximum expansion requirements:
􀂾 Fly Ash ( Class F):
20 percent ( minimum) by weight of cement only for binary blends
12 percent ( minimum) by weight for ternary blends as long as the total
pozzolan dosage is at least 20 percent.
􀂾 Blended Cement:
20 percent ( minimum) by weight of cement only
Proof shall be provided that the blended cement contains the
appropriate percent of fly ash to mitigate ASR.
􀂾 GGBFS:
Not less than 25 percent by weight of cement only
􀂾 Silica Fume:
Not less than 10 percent by weight of cement only
􀂾 Lithium
The Contractor may use lithium nitrate ( LiNO3) as an admixture to
control expansions caused by reactive aggregate. Lithium shall be used
in the form of a solution consisting of 30 percent, by weight, LiNO3. If
used, it shall be used at a dosage rate of 4.6 L of solution for each kg
( 0.55 gal. / lb) of sodium equivalent, as determined from the cement
mill certificate.
• The effectiveness of the admixture( s) in controlling deleterious expansion
shall be determined by mortar bars made and tested using the cement, fly
ash, other mitigating admixtures and the proposed aggregate intended for
use in the proposed concrete mixture.
48
Texas
Rigid Pavements and Concrete Materials Branch
512- 506- 5858
Link to State Specifications Website:
http:// www. dot. state. tx. us/ business/ specifications. htm
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland
Cement Concrete ( PCC):
Aggregate
• Supply aggregates that meet the definitions in Tex- 100- E.
• Aggregates should be free from injurious amounts of alkali.
• Test both coarse and fine aggregate separately in accordance with ASTM C
1260. The test result for each aggregate should not exceed 0.10 percent
expansion.
Coarse Aggregate
Coarse aggregate shall be tested in accordance with Tex- 411- A and shall not
have a 5- cycle magnesium sulfate soundness of more than 18 percent. Crushed
recycled hydraulic cement concrete is not subject to the 5- cycle soundness test.
Fine Aggregate
Limit recycled crushed concrete fine aggregate to a maximum of 20 percent of the
fine aggregate.
Water
• Furnish mixing and curing water that is free from oils, acids, organic matter,
or other deleterious substances.
• Water should be free from alkali.
• Sulfate concentration tested according to ASTM D516 should be less than
1,000 ppm.
• Alkalies ( Na2O + 0.658K2O) concentration tested according to ASTM D
4191 and D 4192 should be less than 600 ppm.
Cement
• Furnish cement conforming to DMS- 4600, “ Hydraulic Cement.”
• When using hydraulic cement only, ensure that the total alkali contribution
from the cement in the concrete does not exceed 4.00 lb/ yd3 of concrete.
49
• When sulfate- resistant concrete is required, use mix design options 1, 2, 3, or
4 given in Section 421.4. A. 6, “ Mix Design Options,” using Type I/ II, II,
V, IP, or IS cement.
• Do not use Class C fly ash in sulfate- resistant concrete.
Supplementary Cementitious Materials
• Furnish fly ash conforming to DMS- 4610, “ Fly Ash.”
• Furnish Ultra- Fine Fly Ash ( UFFA) conforming to DMS- 4610, “ Fly Ash.”
• Furnish Ground Granulated Blast- Furnace Slag GGBFS conforming to
DMS- 4620, “ Ground Granulated Blast- Furnace Slag,” Grade 100 or 120.
• Furnish silica fume conforming to DMS- 4630, “ Silica Fume.”
• Furnish metakaolin conforming to DMS- 4635, “ Metakaolin.”
• Furnish chemical admixtures conforming to DMS- 4640, “ Chemical
Admixtures for Concrete.” Do not use calcium chloride.
• For structural concrete designed using more than 520 lb/ yd3 of
cementitious material, use one of the mix design Options 1– 8 shown
below.
• For concrete classes not identified as structural concrete and designed
using less than 520 lb/ yd3 of cementitious material, use one of the mix
design Options 1– 8, except that Class C fly ash may be used instead of
Class F fly ash for Options 1, 3, and 4 unless sulfate- resistant concrete is
required.
Option 1. Replace 20 to 35 percent of the cement with Class F fly ash.
Option 2. Replace 35 to 50 percent of the cement with GGBFS.
Option 3. Replace 35 to 50 percent of the cement with a combination
of Class F fly ash, GGBFS, or silica fume. However, no more than 35
percent may be fly ash, and no more than 10 percent may be silica
fume.
Option 4. Use Type IP or Type IS cement. ( Up to 10 percent of a Type
IP or Type IS cement may be replaced with Class F fly ash, GGBFS,
or silica fume.)
Option 5. Replace 35 to 50 percent of the cement with a combination
of Class C fly ash and at least 6 percent of silica fume, UFFA, or
metakaolin. However, no more than 35 percent may be Class C fly
ash, and no more than 10 percent may be silica fume.
Option 6. Use a lithium nitrate admixture at a minimum dosage of 0.55
gal of 30 percent lithium nitrate solution per pound of alkalis present
in the hydraulic cement.
50
Option 7. When using hydraulic cement only, ensure that the total
alkali contribution from the cement in the concrete does not exceed
4.00 lb/ yd3 of concrete.
Option 8. For any deviations from Options 1– 7, perform the following:
• Test both coarse and fine aggregate separately in accordance
with ASTM C 1260, using 440 g of the proposed cementitious
material in the same proportions of hydraulic cement to
supplementary cementing material to be used in the mix.
• Before use of the mix, provide the certified test report signed
and sealed by a licensed professional engineer demonstrating
that the ASTM C 1260 test result for each aggregate does not
exceed 0.10 percent expansion.
Utah
George Lukes
Materials Implementation Engineer
glukes@ utah. gov
801- 965- 4707
Link to State Specifications Website:
http:// www. udot. utah. gov/ main/ f? p= 100: pg: 226170755633650::: 1: T, V: 30
2,
The following sections contain excerpts from the specifications that relate to
mitigation of Alkali Silica Reactivity ( ASR) and Sulfate Attack in Portland
Cement Concrete ( PCC):
Aggregate
Coarse Aggregate
Determine the suitability of coarse aggregate sources using the requirements for
soundness, percentage of wear, and potential reactivity as specified in AASHTO
M 80.
Fine Aggregate
The fine aggregates should meet the requirements of AASHTO M 6.
Water
• Limit maximum sulfate concentration as SO4 to 3000 ppm.
• Use potable water or water meeting ASTM C 1602, including Table 2.
51
Cement
• Use Type II Portland cement, or blended Portland cement, unless otherwise
specified.
• Follow the requirements of Table 2 of ASTM C 150 for low- alkali cement.
• When blended cement is substituted for Portland cement, use ASTM C 1567
to verify that expansion is less than 0.1 percent at 16 days.
• Use cement from the list of UDOT pre- qualified sources maintained by the
UDOT Materials Quality Assurance Section.
Supplementary Cementitious Materials
• May use Class N natural pozzolan instead of fly ash provided that the 14- day
expansion test ( ASTM C 1567) with job aggregates and job cement does
not exceed 0.1 percent.
• May use silica fume conforming to ASTM C 1240.
• Maximum allowable CaO content in fly ash not to exceed 15 percent.
• Use Class F fly ash to replace 20 percent of Portland cement by weight.