Sponsor: NC Department of Transportation
Start Date: 8/01/23
End Date: 12/31/25
Abstract
Alkali Silica Reaction (ASR) is one of the most ubiquitous deterioration problems and is a major concern for Department of Transportation (DoTs) across the US. Since the first documentation of ASR in 1940 by T.E. Stanton [1], published based on his investigations of cracking of concrete structures in California, a plethora of papers and data have been published in the literature. While a good understanding of ASR has been established today, evaluating aggregates for the potential of ASR remains elusive. The first line of defense against ASR remains avoiding the use of aggregates with a known history of ASR and/or restricting the alkali content of concrete mixes. The use of accelerated test methods are deemed less reliable than the use of historical data and evidence, due to current test methods assessing aggregate reactivity, not concrete mixture reactivity as used in the field. The main challenge with accelerated test methods is that the mechanism of ASR seems to be very sensitive to perturbation and can change depending on the conditions of the test such as increased temperature, concentration of alkalis, and ion leaching from concrete during the test. As a consequence, rapid tests suffer from low fidelity (e.g., ASTM C 1260), and reliable tests (e.g., ASTM C 1293) are often very time consuming and may take up to two years to complete, which in many instances defeats the purpose of running the test to being with (i.e. the project is already constructed by the time the test is completed). The search for accelerated reliable tests for ASR has occupied researcher for decades.
Unfortunately, many of the currently available accelerated tests rely on the same length change measurement strategy as traditional tests and expose samples to a highly alkali solution at elevated temperatures. Therefore, common accelerated tests all suffer from the same limitations as traditional tests. Additionally, due to the requirement of measuring very fine changes in length, samples must be prepared in a highly controlled manner in the laboratory. The most common test methods are summarized with relevant information in Table 1.