ASR TEST METHODS
Our consultants and laboratory implement various techniques to evaluate a concrete structure's susceptibility to alkali-silica reaction (ASR). Both standardized and novel testing techniques may be used to evaluate the potential for degradation in new and existing structures.
STANDARDS
Standard Guide for Petrographic Examination of Aggregates for Concrete
This guide is used for the identification of rocks and minerals for use in concrete, ASTM C295 provides guidance for detecting constituents that are deleterious to concrete. The analysis is used to identify:
• Chemically Unstable Minerals • Alkali-Silica & Alkali-Carbonate Reactive
• Volumetrically Unstable Materials Constituents
• Freeze Thaw Susceptible Aggregates • Aggregates that Negatively Impact • Aggregates Containing Iron Sulfide Water & Paste Demand
Durability Engineers can perform petrographic analysis to evaluate compliance of aggregates for local, state, or federal project specifications.
Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)
This laboratory test is used for the rapid assessment of an aggregate's susceptibility and potential for degradation associated with alkali-silica reaction (ASR). The mortar bar specimens are stored at 80°C and submerged in an NaOH solution to facilitate a high-alkaline environment. The mortar bar test allows for results within 16 days, indicating the potential for deleterious alkali-silica reaction of the aggregate.
Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction
This laboratory test is used to assess coarse or fine aggregate's susceptibility and potential for degradation associated with alkali-silica reaction (ASR). The test duration is 12 to 24 months long depending if supplementary cementitious materials are incorporated into the mixture. This test is often required by federal and state DOTs for acceptance of new aggregate sources. ASTM C1293 expansion results should serve as a basis for a decision as to whether precautions should be taken against excessive expansion due to alkali-silica reaction.
Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar-Bar Method)
This laboratory test is used for the rapid assessment of an aggregate's susceptibility to ASR combination with supplementary cementitious materials (SCMs). Prepare in the same manner as ASTM C1260, the only variation is the incorporation of SCMs such as fly ash, slag cement or silica fume. It is recommended to run this test in tandem with the same aggregate being evaluated via ASTM C1260. Should the SCM replacement contain elevated alkali content ASTM C1293 is recommended.
Standard Guide for Reducing the Risk of Deleterious Alkali-Aggregate Reaction in Concrete
This guide provides recommendations for identifying the potential alkali-silica reaction (ASR), selecting preventative measures based on prescriptive and/or performance, to minimize the risk of deleterious reaction. The level of prevention is dependent on the reactivity of the aggregate, the nature of the exposure conditions, access to moisture, the criticality of the structure and alkalinity of the cement.
Standard Practice for Petrographic Examination of Hardened Concrete
The standard practice for performing petrographic examination on hardened concrete, ASTM C856, is the industry standard for the evaluation of hardened concrete samples. This method is often used for identifying various issues, including but not limited to:
• Strength Issues • Delamination
• Dying & Plastic Shrinkage • Blistering
• Scaling • Mixture Compliance
Furthermore, ASTM C856 is the only application by which progressive mechanisms of distress can be formally discerned. Mechanisms such as:
• Freeze-Thaw • Corrosion
• Chemical Attack • Sulfate Attack
• Alkali-Silica Reaction & Alkali-Carbonate Reaction