Standard Practice for
Determining the Reactivity of
Concrete Aggregates and Selecting
Appropriate Measures for
Preventing Deleterious Expansion
in New Concrete Construction
AASHTO Designation: R 80-171
Technical Subcommittee: 3c, Hardened Concrete
Release: Group 1 (April)
American Association of State Highway and Transportation Officials
555 12th Street NW, Suite 1000
Washington, DC 20004
Standard Practice for
Determining the Reactivity of Concrete
Aggregates and Selecting Appropriate
Measures for Preventing Deleterious Expansion
in New Concrete Construction
AASHTO Designation: R 80-17 1
Technical Subcommittee: 3c, Hardened Concrete
Release: Group 1 (April)
1.
SCOPE
1.1.
This practice describes approaches for identifying potentially deleteriously reactive aggregates and
selecting appropriate preventive measures to minimize the risk of expansion when such aggregates
are used in concrete. Both alkali–silica reactive and alkali–carbonate reactive aggregates are
covered. Preventive measures for alkali–silica reactive aggregates include avoiding the reactive
aggregate, limiting the alkali content of the concrete, using blended cement, using supplementary
cementitious materials, using lithium nitrate as an admixture, or a combination of these measures.
Preventive measures for alkali–carbonate reactive rocks are limited to avoiding the reactive
aggregate.
1.2.
The values stated in SI units are the preferred standard.
1.3.
This standard may involve hazardous materials, operations, and equipment. This standard does
not purport to address all of the safety concerns associated with its use. It is the responsibility of
the user of this standard to consult and establish appropriate safety and health practices and
determine the applicability of regulatory limitations prior to use.
2.
REFERENCED DOCUMENTS
2.1.
AASHTO Standards:
 M 240M/M 240, Blended Hydraulic Cement
 M 295, Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete
 M 302, Slag Cement for Use in Concrete and Mortars
 M 307, Silica Fume Used in Cementitious Mixtures
 T 303, Accelerated Detection of Potentially Deleterious Expansion of Mortar Bars Due to
Alkali–Silica Reaction
2.2.
ASTM Standards:
 C295/C295M, Standard Guide for Petrographic Examination of Aggregates for Concrete
 C586, Standard Test Method for Potential Alkali Reactivity of Carbonate Rocks as Concrete
Aggregates (Rock-Cylinder Method)
TS-3c
R 80-1
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
 C856, Standard Practice for Petrographic Examination of Hardened Concrete
 C1105, Standard Test Method for Length Change of Concrete Due to Alkali-Carbonate Rock
Reaction
 C1157/C1157M, Standard Performance Specification for Hydraulic Cement
 C1260, Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar
Method)
 C1293, Standard Test Method for Determination of Length Change of Concrete Due to
Alkali-Silica Reaction
 C1567, Standard Test Method for Determining the Potential Alkali-Silica Reactivity of
Combinations of Cementitious Materials and Aggregate (Accelerated Mortar-Bar Method)
2.3.
Canadian Standards:
 CSA A23.2-14A, Potential Expansivity of Aggregates (Procedure for Length Change Due to
Alkali-Aggregate Reaction in Concrete Prisms)
 CSA A23.2-26A, Determination of Potential Alkali-Carbonate Reactivity of Quarried
Carbonate Rocks by Chemical Composition
2.4.
RILEM Recommendation:
 RILEM TC 191-ARP, Alkali-Reactivity and Prevention—Assessment, Specification, and
Diagnosis of Alkali-Reactivity
3.
TERMINOLOGY
3.1.
accelerated mortar-bar test (AMBT)—test method used to determine aggregate reactivity
(AASHTO T 303) or to evaluate the effectiveness of measures to prevent deleterious expansion
when reactive aggregates are used (ASTM C1567).
3.2.
alkali–aggregate reaction (AAR)—chemical reaction in either mortar or concrete between alkalis
(sodium and potassium) present in the concrete pore solution and certain constituents of some
aggregates; under certain conditions, deleterious expansion of concrete or mortar may result. Two
types of AAR are considered in this standard practice; these are alkali–carbonate reaction (ACR)
and alkali–silica reaction (ASR).
3.3.
alkali–carbonate reaction (ACR)—the reaction between the alkalis (sodium and potassium)
present in the concrete pore solution and certain carbonate rocks, particularly argillaceous calcitic
dolomite and argillaceous dolomitic limestone, present in some aggregates; the products of the
reaction may cause deleterious expansion and cracking of concrete.
3.4.
alkali–silica reaction (ASR)—the reaction between the alkalis (sodium and potassium) present in
the concrete pore solution and certain siliceous rocks or minerals, such as opaline chert, strained
quartz, and acidic volcanic glass, present in significant quantities in some aggregates; the products
of the reaction may cause deleterious expansion and cracking of concrete.
3.5.
class of structure—in this guideline, structures are classified on the basis of the severity of the
consequences should ASR occur.
3.6.
concrete prism test (CPT)—test method (ASTM C1293) used to determine aggregate reactivity or
to evaluate the effectiveness of measures to prevent deleterious expansion when reactive
aggregates are used. Another version of this test, ASTM C1105, can be used with a limited alkali
content to determine the potential for alkali–carbonate reactivity.
TS-3c
R 80-2
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
3.7.
deleterious expansion—an increase in volume that is sufficient to cause cracking of the concrete
or result in other problems (e.g., misalignment of adjacent components, closing of joints, etc.).
3.8.
deleteriously reactive—aggregates that undergo chemical reactions in concrete that subsequently
result in deleterious expansion of the concrete.
3.9.
equivalent alkali, Na2Oe—calculated from the sodium (Na2O) and potassium oxide (K2O) as
follows: Na2Oe = Na2O + 0.658 × K2O.
3.10.
nondeleteriously reactive—aggregates with no reactive constituents or minor amounts of reactive
constituents that may exhibit some small amount of reaction without producing significant damage
to the concrete.
3.11.
preventive measures—strategies for suppressing damaging expansion due to alkali–aggregate
reaction (AAR).
3.12.
supplementary cementitious material (SCM)—cementitious materials other than portland cement
(i.e., pozzolans and slag).
4.
SIGNIFICANCE AND USE
4.1.
This practice describes a procedure for evaluating aggregate reactivity and determining measures
to prevent deleterious expansion due to alkali–aggregate reaction (AAR).
4.2.
Following this practice will not completely eliminate the possibility of deleterious expansion
occurring in new construction; rather, the practice provides various approaches for minimizing the
risk of AAR to a level acceptable to the owner.
4.3.
Aggregate reactivity is determined on the basis of one or more of the following: field performance,
petrographic examination, or the expansion testing of mortars or concrete, or both.
4.4.
If the aggregate is deemed to be nondeleteriously reactive, it can be accepted for use in concrete
with no further consideration of preventive measures (assuming that the physical properties of the
aggregate render it suitable for use).
4.5.
If the aggregate is found to be deleteriously reactive, it must then be determined whether the
reaction is of the alkali–carbonate or alkali–silica type.
4.6.
If the aggregate is alkali–silica reactive, the aggregate may be either rejected for use or accepted
with an appropriate preventive measure. There are a number of options for minimizing the risk of
expansion with alkali–silica reactive rocks. This practice allows for preventive measures to be
evaluated on the basis of performance testing or to be selected prescriptively from a list of options
based on previous experience. The level of prevention required is a function of the reactivity of the
aggregate, the class of structure, the nature of the exposure conditions, the availability of alkali in
the system, the type of material used for prevention, and the level of risk the owner is willing to
accept.
4.7.
If the aggregate is alkali-carbonate reactive, the aggregate must be rejected for use. There are no
proven measures for effectively preventing damaging expansion with alkali-carbonate reactive
rocks, and such materials should not be used in concrete without selective quarrying or processing
to limit the reactive components to acceptable levels.
4.8.
In the approach outlined here, the level of testing varies depending on the level of risk that is
acceptable to the owner. For example, in regions where occurrences of AAR are rare or where the
TS-3c
R 80-3
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
aggregate sources in use have a long history of good field performance, it may be reasonable to
continue to rely on the previous field history without subjecting the aggregates to laboratory tests.
However, in regions where AAR problems are known and where the reactivity of aggregates is
known to vary from source to source, it may be necessary to implement a rigorous testing regime
to establish the potential aggregate reactivity and evaluate preventive measures.
5.
GENERAL APPROACH
5.1.
The flow chart in Figure 1 shows the sequence of testing and decisions that has to be made when
evaluating a source of aggregate for potential AAR. It is recommended that the following
sequence of testing is followed to determine aggregate reactivity: consideration of field
performance history, petrographic examination, accelerated mortar-bar testing, and concrete prism
testing. If the rock is a quarried carbonate, additional tests are required to determine the potential
for alkali–carbonate reaction (as shown in Figure 1). Some agencies may adopt one or more of
these test procedures, depending on prior experience with AAR and the acceptable level of risk of
AAR in new construction.
TS-3c
R 80-4
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
a
The type of reaction needs to be determined only after the concrete prism test if the aggregate being tested is a quarried carbonate that
has been identified as being potentially alkali–carbonate reactive by chemical composition in accordance with test method CSA A23.2-26A.
The solid lines show the preferred approach. However, some agencies may want to reduce the amount of testing and accept a higher level
of risk, and this can be achieved by following the direction of the dashed lines.
Figure 1—Sequence of Laboratory Tests for Evaluating Aggregate Reactivity
5.2.
TS-3c
Appropriate preventive measures can be selected either by performance testing using the
accelerated mortar-bar test or concrete prism test, or by using prescribed measures that have been
developed based on previous experience and published research data. The level of prevention
prescribed is a function of the class of the structure, the reactivity of the aggregate, the alkali
content of the portland cement, the composition of the material used for prevention, the exposure
conditions, and the level of risk the owner is willing to accept.
R 80-5
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Note 1—If desired, performance testing can be conducted on the aggregate with preventive
measures, without first establishing aggregate reactivity.
6.
DETERMINING AGGREGATE REACTIVITY
6.1.
Field Performance History:
6.1.1.
The long-term field performance history of an aggregate can be established by consulting the
available documentation (e.g., specifications and construction files) and conducting a survey of
existing structures that were constructed using the same or similar (i.e., from the same geological
environment) aggregate source. As many structures as practical should be included in the survey,
and these structures should, where possible, represent different types of construction (pavements,
sidewalks, curb and gutter, elements of bridges, barrier walls, and even nontransportation
structures). The following information should be collected for each structure: (1) age—structures
should be at least 10 years old and preferably more than 15 years old as deleterious expansion due
to AAR can take more than 10 years to develop; (2) cement content and alkali content of the
cement used during construction; (3) use and type of supplementary cementitious materials during
construction; (4) exposure condition—availability of moisture, use of deicing chemicals; and
(5) presence and type of symptoms of distress due to AAR or other causes.
6.1.2.
Cores should be taken from a representative number of these structures and petrographic
examinations conducted in accordance with ASTM C856 to establish the following: (1) the
presence or not of evidence of deleterious expansion due to AAR, (2) the aggregate used in the
structures surveyed is close in mineralogical composition to that of the aggregate currently being
produced, and (3) the presence and an estimate of the quantity of supplementary cementitious
materials.
6.1.3.
If the results of the field survey indicate that the aggregate is nondeleteriously reactive, the
aggregate may be used in new construction provided that the new concrete is not produced with a
higher alkali loading, a lower amount of or different supplementary cementitious materials, or
more aggressive exposure condition than the structures included in the survey.
6.1.4.
If field performance indicates that an aggregate source is deleteriously reactive, laboratory
expansion testing is required to determine the level of aggregate reactivity and to evaluate
prevention measures.
Note 2—There is a certain level of risk associated with accepting aggregates solely on the basis
of field performance because of difficulties in establishing unequivocally that the materials and
proportions used are similar to those to be used in new construction. For example, petrographic
examination can estimate only the quantity of pozzolans and slag to the nearest 10 percent or so
and is not able to determine the composition of the material (e.g., Class F versus Class C fly ash).
The presence of very finely divided pozzolans (silica fume) cannot be detected using a
petrographic examination.
6.2.
Petrographic Examination:
6.2.1.
Petrographic examination of aggregates should be conducted in accordance with ASTM C295/
C295M. Petrography can reveal useful information about the composition of an aggregate,
including the identification and approximate quantification of reactive minerals.
6.2.2.
Petrography may be used to classify an aggregate as potentially reactive, but expansion testing is
required to determine the extent of potential reactivity and appropriate levels of prevention.
TS-3c
R 80-6
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
6.2.3.
Quarried carbonate rocks should be tested to determine the chemical composition and the potential
for alkali–carbonate reaction in accordance with Section 6.3.
Note 3—Aggregates may be accepted as nondeleteriously reactive solely on the basis of
petrography but there is certain level of risk associated with such a decision, as some reactive
phases may not be routinely detected by optical microscopy (e.g., finely dispersed
cryptocrystalline silica found in some siliceous limestone).
6.3.
Determination of Potential Alkali–Carbonate Reactive Rocks by Chemical Composition:
6.3.1.
If the aggregate being assessed is a quarried carbonate rock, the potential for alkali–carbonate
reaction may be assessed on the basis of its chemical composition using the test method CSA
A23.2-26A. This test involves the determination of the lime (CaO), magnesia (MgO), and alumina
(Al2O3) content of the rock and determining where the composition of the rock falls on a plot of
CaO/MgO ratio versus the Al2O3 content as shown in Figure 2.
6.3.2.
If the composition falls in one of the two ranges identified as “aggregates considered
nonexpansive” in Figure 2, the aggregate is not potentially alkali–carbonate reactive and it should
be tested to determine the potential for alkali–silica reaction using the accelerated mortar-bar test
(Section 6.4) or the concrete prism test (Section 6.5), or both.
6.3.3.
If the composition falls in the range of “aggregates considered potentially expansive,” the
aggregate is potentially alkali–carbonate reactive and must be evaluated further. There are two
options for further testing. One option is to test the aggregate in the concrete prism test, ASTM
C1293 (see Section 6.5), to simultaneously determine the potential for alkali–carbonate and alkali–
silica reactivity. After the test, the prisms are examined by petrography to determine the role
played by the alkali–carbonate reaction (see Section 6.5.5). The second option is to test using the
concrete prism test, ASTM C1105, with a reduced alkali loading to determine the potential for
alkali–carbonate reaction only (see Section 6.6). If the aggregate passes the expansion criteria in
Section 6.6, it is considered not to be alkali–carbonate reactive and can be tested in the same
manner as aggregates with a composition that falls in the two ranges identified as “aggregate
considered nonexpansive” in Figure 2 (see Section 6.3.2).
TS-3c
R 80-7
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Figure 2—Using Chemical Composition as a Basis for Determining Potential Alkali–Carbonate
Reactivity of Quarried Carbonates (from CSA A23.2-26A)
6.4.
Accelerated Mortar-Bar Test (T 303):
6.4.1.
The aggregate may be tested in accordance with T 303 if it meets one of the following three
criteria: (1) the aggregate is not a quarried carbonate, (2) the aggregate is a quarried carbonate
with a composition that falls outside of the region of “aggregates considered potentially
expansive” in Figure 2 when tested in accordance with CSA A23.2-26A, or (3) the aggregate is a
quarried carbonate that does not cause excessive expansion when tested in ASTM C1105 in
accordance with Section 6.6.
6.4.2.
This test is intended to evaluate coarse and fine aggregates separately and should not be used to
evaluate job combinations of coarse and fine aggregates.
6.4.3.
If the expansion of mortar bars following 14 days immersion in sodium hydroxide solution is not
greater than 0.10 percent, the aggregate is considered nondeleteriously reactive and can be
accepted for use (see Note 4).
6.4.4.
If the mortar-bar expansion is greater than 0.10 percent at 14 days, the aggregate is considered to
be potentially deleteriously reactive and its reactivity should be confirmed by testing in ASTM
C1293 (Section 6.5). If there is insufficient time or resources to run ASTM C1293, the aggregate
should be treated as potentially reactive and appropriate preventive measures must be selected.
Note 4—Many aggregates fail the accelerated mortar-bar test (14-day expansion >0.10 percent)
but do not cause deleterious expansion in concrete. An aggregate should not be rejected solely on
the basis of this test.
TS-3c
R 80-8
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Note 5—A number of aggregates (e.g., some siliceous sandstones and granite/gneiss) that pass
this test (14-day expansion ≤0.10 percent) have been found to cause deleterious expansion when
used in concrete. There is a level of risk associated with relying solely on this test to identify
reactive aggregates.
Note 6—Some agencies have used a lower expansion limit or an extended test duration, or both,
(e.g., 0.08 percent at 28 days) or a higher expansion limit (e.g., 0.15 percent at 14 days).
6.5.
Concrete Prism Test (ASTM C1293):
6.5.1.
The concrete prism test is suitable for evaluating all aggregate types and is considered to be the
most reliable laboratory test for predicting the field performance of aggregates. The test should be
conducted in accordance with ASTM C1293.
6.5.2.
If the aggregate being tested is a coarse aggregate, it is blended with a nondeleteriously reactive
fine aggregate for testing. Similarly, if the aggregate being tested is a fine aggregate, it is blended
with a nondeleteriously reactive coarse aggregate for testing. The coarse-fine aggregate
combination is used to produce concrete prisms that have a specified high alkali loading.
6.5.3.
If the expansion of concrete prisms is not greater than 0.04 percent after 1 year, the aggregate is
considered nondeleteriously reactive and may be used in concrete with no further testing (for ASR
or ACR).
6.5.4.
If the expansion of concrete prisms is greater than 0.04 percent after 1 year, the aggregate is
considered to be alkali–silica reactive provided it meets one of the following three criteria: (1) the
aggregate is not a quarried carbonate, (2) the aggregate is a quarried carbonate with a composition
that falls outside of the region of “aggregates considered to be potentially expansive” in Figure 2
when tested in accordance with CSA A23.2-26A, or (3) the aggregate is a quarried carbonate that
does not cause excessive expansion when tested in ASTM C1105 in accordance with Section 6.6.
Preventive measures are required if the aggregate is to be used in concrete construction (see
Sections 7 and 8).
6.5.5.
If the expansion of concrete prisms is greater than 0.04 percent after 1 year and the aggregate
tested was a quarried carbonate rock with a chemical composition that fell within the region of
“aggregates considered potentially reactive,” the concrete prisms must be examined by an
experienced petrographer to determine whether alkali–carbonate reaction contributed to the
expansion. If damaging ACR is detected, either in isolation or in combination with ASR, the
aggregate should not be used in concrete without selective quarrying or processing to limit the
reactive components to acceptable levels. If ASR is determined to be the only cause of expansion
of the concrete, preventive measures are required if the aggregate is to be used in concrete
construction (see Sections 7 and 8). The use of ASTM C1105 may be used as an option to ASTM
C1293 for determining the potential for alkali–carbonate reaction (see Section 6.6).
6.6.
Concrete Prism Test for Alkali–Carbonate Reaction (ASTM C1105):
6.6.1.
The aggregate shall be tested using ASTM C1105, but the alkali content of the concrete shall be
kept below 1.8 kg/m3 (3.0 lb/yd3) Na2Oe to ensure that ASR does not occur. It is preferred that the
test be run for a duration of 12 months, but expansion values at earlier ages may be used if
necessary.
6.6.2.
If the expansion of the cement-aggregate combination is equal to or greater than 0.025 percent at
6 months or 0.030 percent at 1 year, the aggregate shall be considered to be alkali–carbonate
reactive and shall not be used in concrete.
TS-3c
R 80-9
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
6.6.3.
If the expansion of the concrete prisms does not exceed the values set forth in Section 6.6.2, the
aggregate shall be considered not to be alkali–carbonate reactive and should be tested to determine
the potential for alkali–silica reactivity using the accelerated mortar-bar test (T 303) or the
concrete prism test (ASTM C1293), or both, in accordance with Sections 6.4 and 6.5.
7.
SELECTING PREVENTIVE MEASURES FOR ALKALI–SILICA
REACTION (ASR)—PERFORMANCE APPROACH
7.1.
Using the Concrete Prism Test (ASTM C1293) to Evaluate Preventive Measures:
7.1.1.
The concrete prism test may be used to evaluate the efficacy of supplementary cementitious
materials (SCM), such as pozzolans and slag, blended cements (containing SCM), and lithium
nitrate admixtures for preventing damaging alkali–silica reaction. It is prudent to conduct a
number of tests using varying levels of SCM or lithium nitrate to determine the amount required to
prevent deleterious expansion.
7.1.2.
When testing blended cement or supplementary cementitious materials (SCM), the test should be
conducted in accordance with ASTM C1293 (see Note 7).
7.1.3.
When testing lithium nitrate admixtures, the admixture should be added to the mix water and
necessary corrections should be made to account for the water in the admixture. The test should
otherwise be conducted in accordance with ASTM C1293 (see Note 7). See Appendix X2 on
calculation of lithium nitrate additions.
7.1.4.
If the expansion of concrete prisms is not greater than 0.04 percent after 2 years, the combination
of SCM or lithium nitrate admixture and reactive aggregate is considered acceptable for use in
concrete construction provided that the (equivalent) alkali content of the portland cement used in
the job mixture does not exceed 1.00 percent Na2Oe.
Note 7—If a reactive aggregate is to be used in a job mixture that contains a cement with an
alkali content in excess of 1.00 percent Na2Oe, the test procedure of ASTM C1293 should be used
with the following modifications. The job cement should be used in the test and the cement alkalis
should be raised by 0.25 percent Na2Oe above the alkali content of the job cement by the addition
of NaOH to the mix water.
7.1.5.
If the expansion of concrete prisms is greater than 0.04 percent after 2 years, the preventive
measure is not deemed to be effective with the reactive aggregate. Consideration should be given
to retesting the aggregate with an increased level of SCM or lithium nitrate.
7.2.
Using the Accelerated Mortar-Bar Test (T 303) to Evaluate Preventive Measures:
7.2.1.
Before the accelerated mortar-bar test (AMBT) is used to determine the performance of a specific
blended cement-aggregate, SCM-aggregate, or lithium nitrate-aggregate combination, it is
recommended that it first be demonstrated that the aggregate being evaluated responds well to the
accelerated test. This requires a comparison of the results from the accelerated mortar-bar test and
the concrete prism test for the aggregate being used (without preventive measures). After
subjecting the aggregate to both tests, the results are plotted on Figure 3. If data do not fall within
Zone 3 indicated in Figure 3, accelerated mortar-bar test (ASTM C1567) can then be used to
determine efficacy of blended cements, SCMs, and lithium nitrate. Neglecting to perform this type
of comparison may result in either: (1) an overly conservative estimate of aggregate reactivity
using AMBT, resulting in overestimation of required SCM or lithium nitrate amounts or (2) a less
conservative estimate of aggregate reactivity using AMBT, resulting in underestimation of
required SCM or lithium nitrate amounts. This represents an inherent risk in relying solely on the
results of accelerated mortar-bar test or concrete prism test. The results from the accelerated
TS-3c
R 80-10
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
mortar-bar test and the concrete prism test should be compared every 2 years unless the results of
petrography or other tests indicate a significant change in the composition of the material in the
quarry, in which case new tests should be commenced immediately. If there is insufficient time to
conduct a comparison between the two tests, then the accelerated mortar-bar test can be used;
however, there is an increased level of risk associated with making decisions based on this test
alone.
Figure 3—Comparison of AMBT and CPT Data for the Purpose of Determining Whether
the AMBT Is Suitable for Evaluating Preventive Measures with a Specific Aggregate
7.2.2.
The effectiveness of blended cements or supplementary cementitious materials in controlling
damaging expansion shall be determined in accordance with ASTM C1567.
7.2.3.
If the expansion of mortar bars containing blended cement or supplementary cementitious
materials is not greater than 0.10 percent after 14 days in sodium hydroxide solution, the
combination of blended cement or SCM and reactive aggregate shall be considered acceptable for
use in concrete construction provided the alkali content of the portland cement used in the job does
not exceed 1.00 percent Na2Oe.
Note 8—If a reactive aggregate is to be used in a job mixture that contains a cement with an
alkali content in excess of 1.00 percent Na2Oe, the job cement should be used in the test.
7.2.4.
If the expansion of mortar bars containing blended cement or supplementary cementitious
materials is greater than 0.10 percent after 14 days in sodium hydroxide solution, the blended
cement or level of SCM tested is not deemed to be effective with the reactive aggregate.
Consideration should be given to retesting the aggregate with an increased level of SCM, a
different blended cement, or a combination thereof.
7.2.5.
When using the accelerated mortar-bar test to determine the lithium nitrate dose required with a
specific aggregate, the approach proposed by Tremblay et al. (2008) is recommended; the
procedure is as follows:
7.2.5.1.
Test the aggregate using the standard accelerated mortar-bar test (T 303). Extend the duration of
the test such that the mortar bars are exposed to sodium hydroxide for a period of 28 days. Let
E1 = expansion of bars without lithium nitrate at 28 days.
TS-3c
R 80-11
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
7.2.5.2.
Test the aggregate in a modified version of the accelerated mortar-bar test. In this test add
sufficient lithium nitrate to the mortar-bar mixture and the soak solution to achieve lithium-toalkali molar ratios of [Li]/[Na + K] = 0.74 in the mortar and [Li]/[Na + K] = 0.148 in the soak
solution. (See Appendix X2 on calculation of lithium nitrate additions.) Conduct the rest of the test
in accordance with T 303, extending the period in sodium hydroxide to 28 days. Let E2 =
expansion of bars with lithium nitrate at 28 days.
Note 9—To achieve [Li]/[Na + K] = 0.74 in the mortar add 4.6 L of 30 percent-LiNO3 solution
for every 1 kg of alkali (as Na2Oe) in the mix (70.4 fl oz of 30 percent-LiNO3 solution for every
1 lb of alkali).
7.2.5.3.
If (E2 – E1)/E1 <0.1, then use the following lithium-to-alkali molar ratio in the job mix:
[Li]/[Na + K] = 1.0 + 0.7[(E2 – E1)/E1]
7.2.5.4.
If (E2 – E1)/E1 ≥0.1, then use the concrete prism test to determine the lithium nitrate content
required (see Section 7.1).
8.
SELECTING PREVENTIVE MEASURES FOR ALKALI–SILICA
REACTION (ASR)—PRESCRIPTIVE APPROACH
8.1.
The level of prevention is determined by considering the class, size, and exposure condition of the
structure; the degree of aggregate reactivity and the level of alkalis from the portland cement
(when SCMs are used as preventive measures). Worked examples using the prescriptive approach
are given in Appendix X4.
8.2.
Aggregate Reactivity:
8.2.1.
The degree of alkali–silica reactivity of an aggregate is determined by testing the aggregate in the
concrete prism test (Section 6.5) and using the expansion value at 1 year. If data from the concrete
prism test are not available, the degree of reactivity may be determined by testing the aggregate in
the accelerated mortar-bar test (Section 6.4). If data are not available from either test, the
aggregate may be considered as very highly reactive (R3). Aggregate-reactivity classes are given
in Table 1. Where the coarse and fine aggregates are of different reactivity, the level of prevention
should be selected for the most reactive aggregate.
Table 1—Classification of Aggregate Reactivity
Description of Aggregate
Reactivity
Aggregate-Reactivity Class
R0
R1
R2
R3
1-Year Expansion in CPT,
%
Nonreactive
Moderately reactive
Highly reactive
Very highly reactive
14-Day Expansion in
AMBT, %
≤0.04
>0.04, ≤0.12
>0.12, ≤0.24
>0.24
≤0.10
>0.10, ≤0.30
>0.30, ≤0.45
>0.45
8.3.
Risk of ASR:
8.3.1.
The risk of ASR occurring in a structure is determined by considering the aggregate reactivity and
the exposure conditions using Table 2.
TS-3c
R 80-12
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Table 2—Determining the Level of ASR Risk
Size and Exposure Conditions
Aggregate-Reactivity Class
R1
R2
R0
Nonmassive concretea in a dry environmentb
Massive elementsa in a dry environmentb
All concrete exposed to humid air, buried or immersed
All concrete exposed to alkalis in servicec
Level 1
Level 1
Level 1
Level 1
Level 1
Level 2
Level 3
Level 4
Level 2
Level 3
Level 4
Level 5
R3
Level 3
Level 4
Level 5
Level 6
A massive element has a least dimension >0.9 m (3 ft).
A dry environment corresponds to an average ambient relative humidity lower than 60 percent, normally found only in buildings.
Examples of structures exposed to alkalis (sodium and potassium) in service include marine structures exposed to seawater and highway structures exposed to
deicing salts (e.g., NaCl) or anti-icing salts (e.g., potassium acetate, potassium formate, sodium acetate, sodium formate, etc.).
a
b
c
8.4.
Level of Prevention:
8.4.1.
The level of prevention required is determined from Table 3 by considering the risk of ASR from
Table 2 together with the class of structure from Table 4.
Table 3—Determining the Level of Prevention
Level of ASR Risk
(Table 2)
Risk level 1
Risk level 2
Risk level 3
Risk level 4
Risk level 5
Risk level 6
S1
V
V
V
W
X
Y
Classification of Structure (Table 4)
S2
S3
V
V
W
X
Y
Z
V
W
X
Y
Z
ZZ
S4
V
X
Y
Z
ZZ
a
It is not permitted to construct a Class S4 structure (see Table 4) when the risk of ASR is Level 6. Measures must be taken to
reduce the level of risk in these circumstances.
The levels of prevention V, W, X, Y, Z, and ZZ are used in Tables 5 to 8.
a
Table 4—Structures Classified on the Basis of the Severity of the Consequences Should ASR Occura
(Modified for Highway Structures from RILEM TC 191-ARP)
Class
S1
S2
S3
S4
a
b
Consequences of ASR
Acceptability of ASR
Examplesb
Safety, economic, or
environmental consequences
small or negligible
Some safety, economic, or
environmental consequences if
major deterioration
Significant safety, economic, or
environmental consequences if
minor damage
Some deterioration from ASR may be
tolerated.
Non–load-bearing elements inside buildings
Temporary structures (e.g., <5 years)
Moderate risk of ASR is acceptable.
Sidewalks, curbs, and gutters
Service life <40 years
Minor risk of ASR acceptable.
Serious safety, economic, or
environmental consequences if
minor damage
ASR cannot be tolerated.
Pavements
Culverts
Highway barriers
Rural, low-volume bridges
Large numbers of precast elements where
economic costs of replacement are severe
Service life normally 40 to 75 years
Major bridges
Tunnels
Critical elements that are very difficult to inspect
or repair
Service life normally >75 years
This table does not consider the consequences of damage due to ACR. This practice does not permit the use of alkali–carbonate aggregates.
The types of structures listed under each class are meant to serve as examples. Some owners may decide to use their own classification system. For example,
sidewalks or curbs and gutters may be placed in the Class S3.
TS-3c
R 80-13
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Note 10—Structures are classified on the basis of the severity of the consequences should ASR
occur. For example, the consequences of ASR are far more severe for a reinforced concrete bridge
element than they are for a sidewalk. As such, more onerous measures are required to prevent
damaging ASR in a bridge.
8.5.
Requirements for Prevention Level V:
8.5.1.
No special measures need to be taken for prevention level V.
8.6.
Requirements for Prevention Level W, X, or Y:
8.6.1.
If it is determined that prevention level W, X, or Y is required, there are two options for
prevention as follows:
8.6.1.1.
Option 1—Limiting the Alkali Content of the Concrete:
Table 5 prescribes maximum permissible concrete alkali contents. The alkali content of concrete is
calculated on the basis of the alkali contributed by the portland cement alone. For blended cement,
the alkali available from the portland cement component of the blend should be used.
Table 5—Maximum Alkali Contents in Portland Cement Concrete to Provide
Various Levels of Prevention
Prevention Level
V
W
X
Y
Za
ZZa
a
Maximum Alkali Content of Concrete (Na2Oe)
kg/m3
lb/yd3
No limit
3.0
2.4
1.8
Table 8
Table 8
No limit
5.0
4.0
3.0
Table 8
Table 8
SCMs must be used in prevention levels Z and ZZ.
Note 11—The alkali content of the concrete is calculated by multiplying the portland cement
content of the concrete by the alkali content of the portland cement. For example, for concrete
containing 300 kg/m3 of portland cement, which has an alkali content of 0.91 percent Na2Oe, the
alkali content of the concrete is 300 × 0.91/100 = 2.73 kg/m3 Na2Oe. The alkali content in pounds
per cubic yard (lb/yd³) is calculated by multiplying the cement content of the concrete in lb/yd3 by
the alkali content of the cement divided by 100. For example, for a concrete containing 550 lb/yd3
of portland cement, which has an alkali content of 0.82 percent Na2Oe, the alkali content of the
concrete is 550 × 0.82/100 = 4.51 lb/yd3 Na2Oe.
Note 12—Other components of the mix, such as aggregates, wash water, and chemical
admixtures, may contribute alkalis to the concrete and such alkalis should be considered when
calculating the alkali content of the concrete. Supplementary cementing materials also contain
alkalis; however, the use of SCM usually increases the amount of alkalis bound by the hydrates
and thus reduces the available alkali content in the concrete. Thus, the alkalis present in SCMs
need not be considered when calculating the alkali content of the concrete. However, the alkali
content of the SCM should not exceed the limits given in Table 6.
TS-3c
R 80-14
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Table 6—Minimum Levels of SCM to Provide Various Levels of Prevention
Type of
SCMa
Fly ash
(CaO ≤18%)
Slag
Silica fumec
(SiO2 ≥85%)
a
b
c
Alkali Level of SCM,
(% Na2Oe)
≤3.0
>3.0, ≤4.5
≤1.0
≤1.0
Minimum Replacement Levelb (% by Mass of Cementitious Material)
Level W
Level X
Level Y
Level Z
Level ZZ
15
20
25
2.0 × KGA
or
1.2 × LBA
20
25
35
2.5 × KGA
or
1.5 × LBA
25
30
50
3.0 × KGA
or
1.8 × LBA
35
40
65
4.0 × KGA
or
2.4 × LBA
Table 7
Table 7
Table 7
Table 7
The SCM may be added directly to the concrete mixer or it may be a component of a blended cement. SCMs should meet the requirements of M 295, M 302, or
M 307. Blended cements should meet the requirements of M 240M/M 240 or ASTM C1157.
The use of high levels of SCM in concrete may increase the risk of problems due to deicer salt scaling if the concrete is not properly proportioned, finished,
and cured.
The minimum level of silica fume (as a percentage of cementitious material) is calculated on the basis of the alkali (Na2Oe) content of the concrete contributed
by the portland cement and expressed in either units of kg/m3 (KGA in Table 6) or lb/yd3 (LBA in Table 6). KGA is calculated by multiplying the cement content
of the concrete in kg/m3 by the alkali content of the cement divided by 100. For example, for a concrete containing 300 kg/m3 of cement with an alkali content of
0.91 percent Na2Oe, the value of KGA = 300 × 0.91/100 = 2.73 kg/m3. For this concrete, the minimum replacement level of silica fume for Level X is 2.5 ×
2.73 = 6.8 percent. LBA is calculated by multiplying the cement content of the concrete in lb/yd3 by the alkali content of the cement divided by 100. For
example, for a concrete containing 500 lb/yd3 of cement with an alkali content of 0.81 percent Na2Oe the value of LBA = 500 × 0.81/100 = 4.05 lb/yd3. For this
concrete, the minimum replacement level of silica fume for Level Y is 1.8 × 4.05 = 7.3 percent. Regardless of the calculated value, the minimum level of silica
fume shall not be less than 7 percent when it is the only method of prevention.
8.6.1.2.
Option 2—Using Supplementary Cementitious Materials or Blended Cements:
8.6.1.2.1.
Table 6 prescribes minimum replacement levels for fly ash with calcium content not greater than
18 percent CaO and alkali content not greater than 4.5 percent Na2Oe, and for slag and silica fume
with alkali content not greater than 1.00 percent Na2Oe.
8.6.1.2.2.
Fly ashes with greater than 18 percent CaO or greater than 4.5 percent Na2Oe and slag and silica
fume with greater than 1.00 percent Na2Oe are not covered by these prescriptive measures; the
ability of these materials to control ASR with a particular reactive aggregate should be determined
by performance testing (see Section 7).
8.6.1.2.3.
When natural pozzolans are to be used to control ASR, the efficacy of a particular aggregatepozzolan combination should be determined by performance testing (see Section 7).
8.6.1.2.4.
When two or more SCMs (including SCMs in blended cements) are used together to control ASR,
the minimum replacement levels given in Table 6 for the individual SCMs may be reduced
provided the sum of the parts of each SCM is greater than or equal to 1.
Note 13—For example, when silica fume and slag are used together, the silica fume level may be
reduced to one third of the minimum silica fume level given in the table provided the slag level is
at least two thirds of the minimum slag level.
8.6.1.2.5.
The minimum replacement levels in Table 6 are appropriate for use with portland cements of
moderate to high alkali contents (0.70 to 1.00 percent Na2Oe). Table 7 provides recommendations
for adjusting the level of SCM when the alkali content of the portland cement is above or below
this range. The replacement levels should not be below those given in Table 6 for prevention level
W, regardless of the alkali content of the portland cement.
TS-3c
R 80-15
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
Table 7—Adjusting the Minimum Level of SCM Based on the Alkali Content
of the Portland Cement
Cement Alkalis
(% Na2Oe)
≤0.70
>0.70, ≤1.00
Use the minimum levels of SCM given in Table 6.
>1.00, ≤1.25
Increase the minimum amount of SCM given in
Table 6 by one prevention level.
>1.25
a
Level of SCM
Reduce the minimum amount of SCM given in
Table 6 by one prevention level.a
No guidance is given.
The replacement levels should not be below those given in Table 6 for prevention level W, regardless of the
alkali content of the portland cement.
No guidance is given for using preventive measures with reactive aggregates when the alkali
content of the portland cement exceeds 1.25 percent Na2Oe.
Note 14—If this approach is used for portland cements with alkali contents in excess of 1.25
percent Na2Oe, there will be an increased risk of damaging ASR.
8.7.
Requirements for Prevention Level Z:
8.7.1.
If it is determined that prevention level Z is required, there are two options: (1) use the minimum
level of supplementary cementitious material shown in Table 6 or (2) use the minimum level of
supplementary cementitious material and the maximum concrete alkali content shown in Table 8.
Table 8—Using SCM and Limiting the Alkali Content of the Concrete to Provide Exceptional
Levels of Prevention
SCM as Sole Prevention
Prevention
Level
Minimum SCM Level
Limiting Concrete Alkali Content Plus SCM
Maximum Alkali Content, kg/m3
Minimum SCM Level
(lb/yd3)
Z
SCM level shown for
Level Z in Table 6
1.8 (3.0)
ZZ
Not permitted
1.8 (3.0)
SCM level shown for
Level Y in Table 6
SCM level shown for
Level Z in Table 6
8.8.
Requirements for Prevention Level ZZ:
8.8.1.
If it is determined that prevention level ZZ is required, use the minimum level of supplementary
cementitious material and the maximum concrete alkali content shown in Table 8.
9.
REPORTING
9.1.
The report shall list the tests conducted and the results of the tests.
9.2.
If a study was conducted to determine the field performance history of the aggregate, details
should be provided of the structures examined including type, age, visual and photographic
observations, and details of laboratory testing of cores removed from the structure.
9.3.
If a petrographic examination was conducted on the aggregate, the report should be produced in
accordance with ASTM C295/C295M.
TS-3c
R 80-16
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
9.4.
If testing in accordance with CSA A23.2-26A was performed, the lime (CaO), magnesia (MgO),
and alumina (Al2O3) content of the rock shall be reported.
9.5.
If accelerated mortar bar or concrete prism tests were conducted, the results shall be reported in
accordance with the relevant test method (T 303, ASTM C1293, or ASTM C1567).
9.6.
The chemical composition of the cement, SCM, and lithium nitrate admixture used in expansion
tests shall be reported.
10.
KEYWORDS
10.1.
Alkali–aggregate reaction; alkali–carbonate reaction; alkali–silica reaction; concrete; expansion;
fly ash; lithium nitrate; pozzolan; preventive measures; reaction; reactive aggregate; silica fume;
slag.
11.
REFERENCES
11.1.
The following references were used or referred to in the preparation of this text:
11.1.1.
Canadian Standards Association. Potential Expansivity of Aggregates. (Procedure for Length
Change Due to Alkali-Aggregate Reaction in Concrete Prisms). CSA A23.2-14A, Canadian
Standards Association, Mississauga, ON, 2009.
11.1.2.
Canadian Standards Association. Determination of Potential Alkali-Carbonate Reactivity of
Quarried Carbonate Rocks by Chemical Composition. CSA A23.2-26A, Canadian Standards
Association, Mississauga, ON, 2009.
11.1.3.
Canadian Standards Association. Standard Practice to Identify Degree of Alkali-Reactivity of
Aggregates and to Identify Measures to Avoid Deleterious Expansion in Concrete. CSA A23.227A, Canadian Standards Association, Mississauga, ON, 2009.
11.1.4.
FHWA. Report on Determining the Reactivity of Concrete Aggregates and Selecting Appropriate
Measures for Preventing Deleterious Expansion in New Concrete Construction. FHWA-HIF-09001, Federal Highway Administration, U.S. Department of Transportation, Washington, DC,
2008.
11.1.5.
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. Preventing ASR/DEF in New Concrete: Final
Report. The University of Texas at Austin, Center for Transportation Research (CTR),
CTR 4085-5, 2006.
11.1.6.
Ozol, M. A. Alkali-Carbonate Rock Reaction. In Significance of Tests and Properties of Concrete,
STP 169D, Chapter 23. American Society of Testing and Materials, West Conshohocken, PA,
2006, pp. 410–424.
11.1.7.
Rogers, C. A. Evaluation for the potential for expansion and cracking of concrete caused by the
alkali-carbonate reaction. In Journal of Cement, Concrete and Aggregates, Vol. 8, No. 1.
American Society of Testing and Materials, West Conshohocken, PA, 1986, pp. 13–23.
11.1.8.
Thomas, M. D. A., B. Fournier, K. J. Folliard, J. Ideker, and M. Shehata. Test Methods for
Evaluating Preventive Measures for Controlling Expansion due to Alkali-silica Reaction in
Concrete. In Cement and Concrete Research, Vol. 36 (10), Pergamon Press, Elsevier, Inc.,
Burlington, MA, 2006, pp. 1842–1856.
TS-3c
R 80-17
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
11.1.9.
Thomas, M. D. A., B. Fournier, K. J. Folliard, M. Shehata, J. Ideker, and C. A. Rogers.
Performance limits for evaluating supplementary cementing materials using the accelerated mortar
bar test. In ACI Materials Journal, Vol. 104 (2), American Concrete Institute, Farmington Hills,
MI, 2007, pp. 115–122.
11.1.10.
Tremblay, C., M. A. Berube, B. Fournier, M. D. A. Thomas, and K. J. Folliard. Use of the
Accelerated Mortar Test to Evaluate the Effectiveness of LiNO3 against Alkali-Silica Reaction.
Part 2: Comparison with Results from the Concrete Prism Test. In Journal of ASTM International,
Vol. 5 (8), American Society of Testing and Materials, West Conshohocken, PA, 2008.
APPENDIXES
(Nonmandatory Information)
X1.
COMMENTARY
X1.1.
The intention of this commentary is to provide background to the recommended practice and some
level of explanation of the approach adopted in the Practice. A more comprehensive description
and rationalization of the approach of the recommended practice is provided in Report No.
FHWA-HIF-09-001 (Thomas et al., 2008).
X1.2.
The recommended practice basically has two objectives as follows: (1) to determine whether an
aggregate source is deleteriously reactive in concrete as a result of alkali–aggregate reaction
(AAR), whether the reaction is alkali–silica reaction (ASR) or alkali–carbonate reaction (ACR),
and the magnitude of the aggregate reactivity (moderately, highly, or very highly reactive) and
(2) to determine appropriate measures for preventing deleterious ASR if the reactive aggregate is
used in concrete. Preventive measures are provided only for aggregates that are alkali–silica
reactive. There are no generally accepted measures for preventing deleterious reaction with alkali–
carbonate reactive aggregates in concrete.
X1.3.
The recommended practice covers a range of different methodologies that allows the user the
flexibility to select practices that are most applicable to local considerations (e.g., the extent and
range of aggregate reactivity and available materials’ characteristics).
X1.4.
The approach is based on that of the Canadian Standards Association, CSA A23.2-27A, Standard
Practice to Identify Degree of Alkali-Reactivity of Aggregates and to Identify Measures to Avoid
Deleterious Expansion in Concrete and CSA A23.2-28A, Standard Practice for Laboratory Testing
to Demonstrate the Effectiveness of Supplementary Cementing Materials and Lithium-Based
Admixtures to Prevent Alkali-Silica Reaction in Concrete. The CSA approach has evolved over
many decades and was developed to be applicable over a vast geographic area with widely
differing geology and a wide range of aggregate types and cementing materials (Fournier et al.,
2000). Significant laboratory and field data have been used to underpin the CSA guidelines (see
bibliography) and it is believed that the approach is equally applicable to the range of concretemaking materials available in the United States (Lankes et al., 2001; Ideker et al., 2004; Folliard
et al., 2006; Merrill, 2008).
X1.5.
Determining Aggregate Reactivity:
X1.5.1.
The recommended practice allows aggregate reactivity to be determined using four different
approaches. ASTM C1105 may also be used to determine the level of risk of alkali–carbonate
reaction.
TS-3c
R 80-18
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
X1.5.1.1.
Field Performance—If the aggregate source has a long-history of satisfactory performance in the
field, then it is reasonable to assume that it will not cause deleterious reaction in new concrete
provided that the conditions of use do not change;
X1.5.1.2.
Petrographic Evaluation (ASTM C295/C295M)—If known reactive minerals are not observed
when an aggregate source is subjected to a detailed examination, the aggregate is unlikely to cause
deleterious reactions in concrete;
X1.5.1.3.
Accelerated Mortar-Bar Test (T 303)—Aggregates that pass this test generally have a low risk of
producing expansion in the field (although certain coarse aggregates have been found to pass this
test but fail the concrete prism test (Folliard et al., 2006)); and
X1.5.1.4.
Concrete Prism Test (ASTM C1293)—Aggregates that pass this test have a negligible risk of
producing expansion in the field.
X1.5.2.
Owners may decide to adopt any one or more of these tests to determine aggregate reactivity.
However, it should be acknowledged that the level of risk of failing to correctly identify the
reactivity of the aggregate varies depending on the approach adopted. It is generally recognized
that the concrete prism test is the most reliable test for determining the reactivity of an aggregate;
however, the duration of the test (1 year for testing aggregate reactivity) may limit the practical
application of the test in some circumstances. Consequently, many owners may decide to rely on
the more rapid (14-day) accelerated mortar-bar test, field performance, petrographic evaluation, or
a combination of these techniques. For a detailed critique of the different approaches, reference
should be made to Report No. FHWA-HIF-09-001 (Thomas et al., 2008).
X1.5.3.
Quarried carbonates are subjected to a screening test based on chemical composition. If the
chemical composition of the aggregate indicates a potential for alkali–carbonate reactivity, the
aggregate must be tested using the concrete prism test only, as such aggregates do not produce
significant expansion in the accelerated mortar-bar test (Lu et al., 2008). If the aggregate is tested
using ASTM C1293 and deleterious expansion occurs, the concrete must be subjected to a
petrographic evaluation to determine whether the expansion is attributed to alkali–carbonate
reaction. If the aggregate is tested using ASTM C1105 using concrete with low alkali content (see
Section 6.6) and no expansion is observed, the aggregate is not alkali–carbonate reactive and can
be evaluated for alkali–silica reaction using any of the approaches listed above.
X1.5.4.
Although field performance and petrographic examination can provide an indication of the
potential reactivity of an aggregate source, these methods cannot be used to determine the degree
of aggregate reactivity.
X1.5.5.
The expansion limit of 0.04 percent at 1 year is widely used for the concrete prism test. However,
there is some controversy regarding the most appropriate expansion limit for the accelerated
mortar-bar test when used either for determining whether or not an aggregate is deleteriously
reactive or what level of prevention is required to prevent expansion with a reactive aggregate.
This practice uses an expansion limit of 0.10 percent at 14 days for the accelerated mortar-bar test,
as this limit has been found to provide a reasonable correlation with results from tests on concrete
and the performance of concrete in the field (Thomas et al., 2007).
X1.6.
Selecting Preventative Measures:
X1.6.1.
If it is determined that an aggregate is alkali–carbonate reactive, the standard practice recommends
that the aggregate be rejected for use in concrete, as preventive measures are not generally
effective in preventing deleterious expansion with such aggregates. It is possible that deleterious
reaction may be prevented with some sources of alkali–carbonate reactive rock, but this needs to
be documented on a case-by-case basis before such aggregates are used in concrete.
TS-3c
R 80-19
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
X1.6.2.
For alkali–silica reactive aggregates, two approaches are provided to select appropriate measures:
1. Performance Approach—Using either the accelerated mortar-bar test (ASTM C1567) or the
concrete prism test (ASTM C1293) and
2. Prescriptive Approach—Using prescribed measures that are based on previous experience.
The prescriptive approach cannot be used to determine the amount of lithium required to control
expansion. The lithium dose will vary with aggregate source and must be determined by
performance testing of the specific aggregate source with varying amounts of lithium (Tremblay
et al., 2007).
X1.7.
Performance Approach for Selecting Preventive Measures:
X1.7.1.
Either the accelerated mortar-bar test or the concrete prism test may be used to determine the
efficacy of a preventive measure. The preventive measures that may be evaluated are the use of
lithium or supplementary cementing materials (SCM) such as fly ash, slag, silica fume, natural
pozzolans, or combinations thereof. Because of the accelerated nature of the procedures, these
performance tests cannot be used to determine the safe level of alkali (or alkali threshold) for a
given aggregate.
X1.7.2.
Because of the long duration of the concrete prism test (2 years to evaluate preventive measures),
the accelerated mortar-bar test is more commonly used to determine the required level of
prevention. While this approach may be acceptable for most aggregate types, it should be noted
that the accelerated test can produce false positives (indicating deleterious reaction when
expansion would not be observed in concrete) and occasionally false negatives (indicating no
deleterious reaction when expansion may occur in concrete). For this reason, the practice
recommends that the accelerated mortar-bar test be calibrated against the concrete prism test for
the aggregate under test (see Section 7.2.1).
X1.7.3.
When using the accelerated mortar-bar test for evaluating preventive measures, this practice
specifies that the level of prevention is sufficient provided the expansion is not greater than
0.10 percent at 14 days. Some other specifications use a similar expansion limit at 28 days;
however, this longer test duration has not been adopted in this practice because it has been
reported that such an approach significantly overestimates the level of prevention required
(Thomas et al., 2007).
X1.8.
Prescriptive Approach for Selecting Preventive Measures:
X1.8.1.
This approach prescribes the level of prevention (maximum alkali content or minimum level of
SCM) based on the following considerations: (1) aggregate reactivity, (2) size and exposure
conditions of the structure, (3) classification of the structure (based on the severity of the
consequences should ASR occur), and (4) alkali contributed from the portland cement.
X1.8.2.
The level of prevention (e.g., the amount of SCM) increases as the reactivity of the aggregate
increases, the size of structural element increases, the exposure condition of the structure becomes
more aggressive and the criticality of the structure increases. For example, an indoor column
manufactured with a moderately reactive aggregate in a building with a 50-year service life would
require little or no prevention because there is a very low risk of ASR, whereas a bridge deck
produced with a very highly reactive aggregate, exposed to deicing salts and with a 100-year
service life presents a very high risk of ASR and requires the highest level of prevention.
X1.8.3.
The approach to classifying structures on the basis of “the consequences should ASR occur” (see
Table 4) was adopted from that used in RILEM TC 191-ARP Alkali-Reactivity and Prevention—
Assessment, Specification, and Diagnosis of Alkali-Reactivity. The approach presumes that a
higher level of risk of ASR can be accepted in some types of structures. This approach provides a
greater level of flexibility for the owner when selecting preventive measures. For example, when
constructing a major bridge with a 100-year service life, ASR cannot be tolerated because ASR
TS-3c
R 80-20
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
will likely jeopardize the service life and lead to premature rehabilitation. In such a case, if a
reactive aggregate is used, it will be necessary to use a high amount of SCM and possibly even
control the alkali content of the concrete. This could impact the constructability and cost of
construction but it is necessary to ensure durability. If the same aggregate was used in a sidewalk,
a reduced level of SCM with no control of the alkali content may produce an acceptable level of
risk because the consequences of ASR are less severe and are likely not to impact the service life
of the concrete element. Although examples are given in Table 4 of the type of structures that
might fall into the different classes, it is probable that owners will reclassify structural types based
on their own experiences dealing with the consequences of ASR.
X1.8.4.
The levels of prevention prescribed by the Practice are based on similar values used in CSA
A23.2-27A, Standard Practice to Identify Degree of Alkali-Reactivity of Aggregates and to
Identify Measures to Avoid Deleterious Expansion in Concrete. The Canadian guidelines are
based on a significant database developed from laboratory and field testing.
X1.9.
Summary:
X1.9.1.
The recommended practice was developed to provide owners of structures with tools to reduce the
risk of deleterious alkali–aggregate reaction in concrete structures. It is not intended to completely
eliminate all risk of AAR. The objective was to provide flexible guidelines allowing owners to
select the approaches most suitable for a given location. In locations with intensive infrastructure
development, where a wide variety of aggregates are available and there are many existing cases
of AAR, it would be prudent to adopt a rigorous approach based on frequent testing of aggregates
and evaluation of preventive measures. In locations with less construction activity, little variation
in aggregate mineralogy, and with little or no prior history of AAR, it may be sufficient to rely on
previous field performance with periodic petrographic examination of aggregate sources to ensure
that there are no changes in mineralogy. The recommendations put forth in this practice will
undoubtedly change with time as more data become available from laboratory and field studies on
alkali–aggregate reaction.
X1.10.
References:
X1.10.1.
The following references were used or referred to in the preparation of this text:
X1.10.1.1.
Canadian Standards Association. Standard Practice to Identify Degree of Alkali-Reactivity of
Aggregates and to Identify Measures to Avoid Deleterious Expansion in Concrete. CSA A23.227A, Canadian Standards Association, Mississauga, ON, 2009.
X1.10.1.2.
Canadian Standards Association. Standard Practice for Laboratory Testing to Demonstrate the
Effectiveness of Supplementary Cementing Materials and Lithium-Based Admixtures to Prevent
Alkali-Silica Reaction in Concrete. CSA A23.2-28A, Canadian Standards Association,
Mississauga, ON.
X1.10.1.3.
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. Preventing ASR/DEF in New Concrete: Final
Report. The University of Texas at Austin, Center for Transportation Research (CTR), CTR 40855, 2006.
X1.10.1.4.
Fournier, B., M. A. Bérubé, and C. A. Rogers.“CSA Standard Practice to Evaluate Potential
Alkali-Reactivity of Aggregates and to Select Preventive Measures against AAR in New Concrete
Structures. Proc., 11th International Conference on AAR in Concrete, Québec (Canada), 2000,
pp. 633–642.
TS-3c
R 80-21
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
X1.10.1.5.
Ideker, J., K. J. Folliard, M. J. Juenger, and M. D. A. Thomas. Laboratory and Field Experience
with ASR in Texas, USA. Proc., 12th International Conference on Alkali-Aggregate Reactivity
(ICAAR), Beijing, China, 2004, pp. 1062–1070.
X1.10.1.6.
International Union of Laboratories and Experts in Construction Materials, Systems, and
Structures (RILEM). Alkali-Reactivity and Prevention—Assessment, Specification, and Diagnosis
of Alkali-Reactivity, TC 191-ARP.
X1.10.1.7.
Lankes, G. D., E. J. Lukefahr, and M. Won. The Texas DOT Specification for Mitigating ASR.
Proc., International Center for Aggregates Research 9th Annual Symposium: Aggregates—
Concrete, Bases and Fines, 2001.
X1.10.1.8.
Lu, D., B. Fournier, P. E. Grattan-Bellew, Y. Lu, Z. Xu, and M. S. Tang. Expansion Behavior of
Spratt and Pittsburg Limestones in Different Test Procedures. Proc., 13th International
Conference on AAR in Concrete, Trondheim, Norway, 2008.
X1.10.1.9.
Merrill, B. ASR Prevention in Texas. In HPC Bridge Views, Federal Highway Administration,
Sept./Oct. 2008, No. 51.
X1.10.1.10.
Thomas, M. D. A., B. Fournier, K. J. Folliard, M. Shehata, J. Ideker, and C. A. Rogers.
Performance Limits for Evaluating Supplementary Cementing Materials Using the Accelerated
Mortar Bar Test. ACI Materials Journal, American Concrete Institute, Farmington Hills, MI,
2007, Vol. 104, No. 2, pp. 115–122.
X1.10.1.11.
Thomas, M. D. A., B. Fournier, and K. J. Folliard. Report on Determining the Reactivity Of
Concrete Aggregates and Selecting Appropriate Measures for Preventing Deleterious Expansion
in New Concrete Construction. Federal Highway Administration, Report FHWA-HIF-09-001,
National Research Council, Washington, DC, 2008.
X1.10.1.12.
Tremblay, C., M. A. Bérubé, B. Fournier, M. D. A. Thomas, and K. J. Folliard. Effectiveness of
Lithium-Based Products in Concrete Made with Canadian Reactive Aggregates Susceptible to
Alkali-Silica Reactivity. ACI Materials Journal, American Concrete Institute, Farmington Hills,
MI, 2007, Vol. 104, No. 2, pp. 195–205.
X2.
CALCULATING LITHIUM NITRATE ADDITIONS
X2.1.
These calculations assume that the admixture being used is a 30 percent-LiNO3 solution. This is
the only solution commercially available at this time.
X2.2.
Published research indicates that a lithium nitrate dose that results in a lithium-to-sodium-pluspotassium molar ratio of [Li]/[Na + K] = 0.74 will be effective with many, but not all, aggregates.
It is recommended that concrete prism tests be conducted at this lithium nitrate dose and at lower
and higher doses.
X2.3.
To achieve a dose of [Li]/[Na + K] = 0.74 using a 30 percent LiNO3 solution requires 4.6 L of
solution for every kilogram of alkali (as Na2Oe) in the concrete (from the portland cement) or
0.55 gal for every pound of alkali.
X2.4.
A solution of 30 percent LiNO3 contains 70 percent water by mass, and this amount should be
included in the calculation of the batch water. One liter of 30 percent LiNO3 solution weighs
1.2 kg and contains 0.84 kg of water. One gallon of 30 percent LiNO3 solution weighs 10.02 lb
and contains 7.01 lb of water.
TS-3c
R 80-22
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
X2.5.
Metric Example—For a 16-L batch of concrete (typical quantity for CPT) with 420 kg/m3 of
cement raised to 1.25 percent Na2Oe, the quantity of alkali present is 16/1000 × 420 × 1.25/100 =
0.084 kg Na2Oe. To achieve [Li]/[Na + K] = 0.74 in the mix, 4.6 × 0.084 = 0.3864 L of 30 percent
LiNO3 solution needs to be added to the mix. This quantity of solution contains 0.3864 × 0.84 =
0.3246 kg of water that should be subtracted from the mix water.
X2.6.
English Example—For a 0.6 ft3 batch of concrete (typical quantity for CPT) with 708 lb/yd3 of
cement raised to 1.25 percent Na2Oe, the quantity of alkali present is 0.6/27 × 708 × 1.25/100 =
0.197 lb Na2Oe. To achieve [Li]/[Na + K] = 0.74 in the mix, 0.55 × 0.197 = 0.1084 gal of
30 percent LiNO3 solution needs to be added. This quantity of solution contains 0.1084 × 7.01 =
0.7600 lb of water that should be subtracted from the mix water.
X3.
CALCULATING LITHIUM NITRATE ADDITIONS FOR THE MODIFIED
ACCELERATED MORTAR-BAR METHOD (FOR LITHIUM NITRATE
SOLUTIONS)
X3.1.
The calculations below assume that the admixture being used is a 30 percent LiNO3 solution. This
is the only solution commercially available at this time.
X3.2.
In this modified version of the accelerated mortar-bar test, sufficient lithium nitrate shall be added
to the mortar-bar mixture and to the soak solution to achieve: (1) lithium-to-alkali molar ratios of
[Li]/[Na + K] = 0.74 in the mortar and (2) [Li]/[Na + K] = 0.148 in the soak solution (i.e.,
20 percent of the “standard dosage” of 0.74).
X3.3.
Example of Calculation of the Lithium Nitrate Dose in the Mortar—The cement content in the
modified AMBT is 440 g. For a cement with 1 percent Na2Oe, the alkali content for LiNO3
calculation is: 440 g × 1/100 = 4.4 g of Na2Oe. To achieve a dose of [Li]/[Na + K] = 0.74 using a
30 percent LiNO3 solution requires 4.6 L of solution for every kilogram (or 4.6 mL for every
gram) of alkali (as Na2Oe) in the mortar (provided by the portland cement). So 4.4 g of Na2Oe ×
4.6 mL (of LiNO3 solution) = 20.2 mL of LiNO3 solution (= [Li]/[Na + K] of 0.74).
X3.4.
The water content in the LiNO3 solution needs to be accounted for in the calculation of the mortar
mix water. Because 1 mL of 30 percent LiNO3 solution weighs 1.2 g and there is 70 percent water
(by mass in the 30 percent LiNO3 solution), the mass of water in 20.2 mL of LiNO3 solution is
20.2 × 1.2 × 0.7 = 17 g. Because the water/cement ratio to use in the AMBT is 0.47 and the
cement content is 440 g, then the mixing water content is 0.47 × 440 g = 206.8 g – 17 g (water
provided by the LiNO3 solution) = 189.8 g.
X4.
WORKED EXAMPLES FOR SELECTING PREVENTIVE MEASURES
FOR ALKALI–SILICA REACTION (ASR)—PRESCRIPTIVE APPROACH
X4.1.
Example 1—Major Bridge Crossing:
X4.1.1.
Preventive measures are required for a major bridge that is not exposed to deicing salts. When
tested according to ASTM C1293, the coarse and fine aggregates intended for use produced 1-year
expansion values of 0.093 percent and 0.032 percent, respectively. Portland cement with an alkali
content of 0.86 percent Na2Oe and fly ash with a calcium content of 14.1 percent CaO and an
alkali content of 3.51 percent Na2Oe are available.
X4.1.2.
Aggregate Reactivity—Table 1 indicates the coarse aggregate reactivity to be R1 (moderately
reactive) and the fine aggregate to be R0 (nonreactive). Design for worse case: R1.
TS-3c
R 80-23
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO
X4.1.3.
Level of ASR Risk—Table 2 indicates the risk of ASR to be Level 3 for a moderately reactive (R1)
aggregate exposed to humid air, buried or immersed (no deicing salts).
X4.1.4.
Level of Prevention—Table 3 indicates the level of prevention required to be Level Y for an S4
class of structure (Table 4) with an ASR risk of Level 3.
X4.1.5.
Prevention Required—Either control alkali content of concrete or use SCM.
X4.1.5.1.
Option to Limit Alkali Content of Concrete—Table 5 indicates that the maximum alkali content is
3.0 lb/yd3 Na2Oe for prevention level Y. This translates to a maximum cement content of
3/(0.86/100) = 349 lb/yd3 for a cement with an alkali content of 0.86 percent Na2Oe (this option is
unlikely to be feasible).
X4.1.5.2.
Option to Use SCM—Table 6 indicates a minimum fly ash replacement of 30 percent for fly ash
with 14.1 percent CaO and 3.51 percent Na2Oe for prevention level Y.
X4.2.
Example 2—Sidewalk Exposed to Deicing Salts:
X4.2.1.
Preventive measures are required for a city sidewalk exposed to deicing salts. When tested in
T 303, the coarse and fine aggregates produce 14-day expansions of 0.35 percent and 0.55 percent,
respectively. Portland cement with an alkali content of 0.38 percent Na2Oe and slag with an alkali
content of 0.71 percent Na2Oe are available.
X4.2.2.
Aggregate Reactivity—Table 1 indicates the coarse aggregate reactivity to be R2 (highly reactive)
and the fine aggregate to be R3 (very highly reactive). Design for worse case: R3.
X4.2.3.
Level of ASR Risk—Table 2 indicates the risk of ASR to be Level 6 for a very highly reactive (R3)
aggregate exposed to alkalis in service (deicing salts).
X4.2.4.
Level of Prevention—Table 3 indicates the level of prevention to be Level Z for an S2 class of
structure (Table 4) with an ASR risk of Level 6.
X4.2.5.
Prevention Required—Use SCM. (Table 5 does not permit the control of the concrete alkali
content as the only prevention measure for prevention level Z.)
X4.2.5.1.
Option to Use SCM—Table 6 indicates a minimum slag replacement of 65 percent for slag for
prevention level Z. Table 7 allows the minimum amount of SCM in Table 6 to be reduced by one
prevention level if the cement alkalis are below 0.70 percent Na2Oe. Therefore, the minimum slag
replacement level is 50 percent (prevention level Y).
1
Formerly AASHTO Provisional Standard PP 65. First published as a full standard in 2017.
TS-3c
R 80-24
© 2020 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
AASHTO