Towards the Improvement of ASR Guidelines

In recent years, long-term exposure sites have shown a disconnect between laboratory test methods and field exposure blocks. To improve standard guidance documents such as ASTM C1778 and AASHTO R80, three universities cast over 450 exposure blocks placed at 8 different exposure sites. These exposure blocks were cast at lower alkali loading levels compared to traditional exposure blocks and included traditional and non-traditional supplementary cementitious materials (SCMs) to prevent ASR. Non-traditional SCMs included natural pozzolans, reclaimed fly ash, and blended fly ashes. New test methods were evaluated as well, so that six test methods will be bench-marked against these new exposure blocks as well as historical (15–20 year) exposure blocks. This paper provides the results of a study aimed at improving the guidance currently contained in ASTM C1778 for mitigating alkali-silica reaction (ASR) in concrete. The improvement to these guidelines were drawn upon an extensive, historic database of laboratory and exposure site data. The results from this study provide recommended changes to both the prescriptive and performance-based approaches for preventing ASR.