AASHTO Guide Specification For Highway Construction
SECTION 56X
Portland Cement Concrete Resistant to Excessive Expansion Caused by Alkali-Silica Reaction (Appendix F to ASR Transition Plan)

Note: Section 56X will be published in the next edition of AASHTO's Guide Specification for Highway Construction. It is presently available only on this web site.

Flow Chart for Portland Cement Concrete Resistant to Deleterious ASR

56X.01 Description. Provide a portland cement concrete (PCC) that is resistant to excessive expansion caused by alkali-silica reactivity¹ (ASR) (hereafter designated as "deleterious ASR").

(1) HPC needs to be ASR resistant where deleterious ASR resistance is a consideration in service. Resistance to deleterious ASR is not a consideration where the concrete will not be exposed to moisture in service.

56X.02 Material.

56X.03 Requirements.

Proportion PCC mixes under Section 808 of this Guide or AASHTO M 157 to include materials that meet either Subsection A or B below. Provide certified material test reports from AASHTO Accredited laboratories that show the cementitious materials' source, composition, and alkali contents.

A. Aggregates.

Assess the potential for deleterious reactivity of the aggregate by evaluation of field performance using the criteria of Table 56X-1(A), or by laboratory evaluation using at least one of the procedures in Table 56X-1(B). Aggregates meeting the criteria for nonreactivity are allowed to be used without restriction. Aggregates not meeting the criteria for nonreactivity shall only be used with cementitious materials meeting the requirements of Subsection B.

Use field performance when available to identify nonreactivity of aggregates. Perform laboratory tests on the aggregates for added confirmation, or when the field performance is unavailable.

Include field performance information using ASTM C 856 from at least 5 structures that have been in service for a minimum of 10 years, including structures that have used cathodic protection. Use caution in concluding that aggregates are nonreactive when using information from structures in service for less than 20 years. Select structures that were built with similar cement factors, water cement ratios, and cement alkali contents to those proposed for use in the mix design, and which were exposed to environments similar to those in which the proposed structure will be built.

B. Deleterious ASR Prevention Criteria.

Select a material or a combination of materials that meet the criteria shown in Table 56 X-2.

Demonstrate under the method options below that the proposed mixture is effective in preventing deleterious ASR. Use the materials proposed for the project. Use the same proportion of cement and mineral admixture for each test mixture as that proposed for the actual mix design. Provide to the Agency certified documentation of the mixture's effectiveness to prevent deleterious ASR.

Method 1. ASTM C 441 Mixture Effectiveness

Determine the selected mixture's effectiveness to prevent deleterious ASR using ASTM C 441, or as modified below. Ensure the total equivalent alkali level of the test mixture is within 0.05 percent of the actual mix.

Assume a test mixture to be effective under any of one of the following ASTM C 441 modifications when its linear expansion:

1. (generally for all cementitious mixes) does not exceed at 56 days :
   
   1. 0.10 percent when the AASHTO T 303 test result for any aggregate to be used with the test mixture is more than 0.50 percent, and
      
   2. 0.15 percent when the AASHTO T 303 test result for all aggregate to be used with the test mixture is less than 0.50 percent, or
2. (generally for fly ash, GGBFS, and silica fume mixes) is less than or equal to the expansion of a comparison control mixture prepared with cement of alkali between 0.40 and 0.60 percent, or
   
3. (generally for low alkali cement mixes) achieves at 14 days a 55 percent minimum reduction in expansion with the selected test mixture as compared to the control mixture using a cement with an alkali content of 1.00 percent plus or minus 0.05 percent.

Method 2. AASHTO T 303 Mixture Effectiveness.

Determine the selected mix proportion's effectiveness to prevent deleterious ASR using AASHTO T 303.

Assume a test mixture to be effective when its linear expansion at 14 days is less than or equal to 0.08 percent for metamorphic aggregates (see Footnote 7 to Table 56X-1), and 0.10 percent for all other aggregates.

Method 3. ASTM C 1293 Mixture Effectiveness.

Determine the selected mix proportion's effectiveness to control ASR using ASTM C 1293.

Add NaOH to the mix water to raise the sodium equivalent (Na₂Oeq) to 1.25 percent by mass of cementitious material as described by ASTM C 1293. When cement portions are replaced with pozzolans or GGBFS, add NaOH to raise the Na₂Oeq using just the cement portion of the cementitious material.¹

Assume a test mixture to be effective when its expansion does not exceed 0.04% linear expansion at two years.

(1)Based on the practice recommended in Canadian Standards Association A23.1-94, Concrete Materials and Methods of Concrete Construction, Appendix B, Section 5.3, Supplementary Cementing Materials. See note at the end of this document for instructions on where to obtain a copy of CSA A23.1-94.

(1) Use ASTM C 856 as a verification check to the visual examination.
(2) In rare occasions, some aggregates known to be reactive in the field may give a false negative in this test, in that the expansion at 14 days may be below the limit that defines the aggregate as reactive. This is usually because the amount of reactive constituent in the aggregate is partially removed by the preparation of the aggregate for the test. As an extra measure, ASTM C 295 may be used to guard against this possibility.
(3) Use a second order polynomial of %Exp = A_O + A₁SQRT(t) + A₂t. See Johnston, D. Alkali Silica Reactivity of Fine Aggregates in South Dakota. South Dakota DOT, Office of Research, Pierre, South Dakota, 1994. Study SD92-04-F.
(4) In some instances, fine aggregates from the upper Midwest which appear to be reactive based on service history do not develop more than 0.04% expansion in the ASTM C 1293 prisms at one year. The prisms made with these fine aggregates, however, develop extensive crack networks on the surface of the prisms, as well as severe popouts from the prism surfaces. ASTM C 1293 prisms that exhibit such damage, but do not develop expansion greater than 0.04% at one year, shall be examined for signs of deleterious ASR development using ASTM C 856.
(5) Use ASTM C 295 as a verification check to either AASHTO T 303 or ASTM C 1293.
(6) Based on the total aggregate sample.
(7) The phrase "metamorphic aggregates" utilized here is not technically correct. However, it is used as a means of keeping the wording in the table to a minimum. "Metamorphic aggregates" is shorthand for "aggregates coming from sources located in or derived from metamorphic rocks". See ASTM C 294 for definitions of what constitute metamorphic rocks.

(1) See Section 56X.03.B for Methods 1, 2, and 3.
(2) Measure this minimum content of cementitious material as percent by mass of cement plus mineral admixture. Waive this minimum a.) when the user agency has established conclusively through testing that use of less than the recommended minimum of any individual mineral admixture will remediate the ASR potential of the aggregates proposed for use and will not result in a pessimum phenomenon; or b.) when used in combination with other mineral admixtures, or lithium admixtures.
(3) Vary the dosage to obtain the optimum effectiveness, and waive this minimum when used in combination with mineral admixtures. Report the final dosage as a percentage of the standard dosage.
(4) Taken from the cement mill run certificate.

56X.04 Measurement.

A. Measure under Subsection 109.01 and as follows:

B. Include all material tests and effectiveness evaluations in the unit of measure.

56X.05 Payment.

NOTE:
This Guide Specification for PCC Resistant to Excessive Expansion Caused by Alkali-Silica Reaction, developed by the AASHTO Lead State Team on ASR over a period from November 1997 through March 1998, is in the form submitted to the AASHTO Subcommittees on Construction and Materials. The ASR Lead State Team has requested that AASHTO consider this for publication in the next edition of the AASHTO Guide Specifications for Highway Construction.

The CSA Standard A23.1-94, Concrete Materials and Methods of Concrete Construction, can be obtained from the Canadian Standards Association, 178 Rexdale, Toronto, Ontario, Canada, M9W 1R3. It can also be obtained from Global Engineering Documents, 15 Inverness Way East, Englewood, CO 80112-5704 (Ph.: 1-800-854-7179; e-mail: global@ihs.com). Both organizations charge a fee for documents.

SHRP publications can be obtained from the FHWA Report Center: