Alkali-silica reaction mitigation: State of the art and recommendations

Alkali-silica reaction (ASR) mitigation techniques from various states in the United States, and from various countries and international organizations, were assessed and summarized. A set of recommended mitigation procedures was developed that requires not only the use of low-alkali cement, but replacement of part of it by Class F fly ash (or Class N pozzolan) (25 to 40% by weight), or ground granulated blast-furnace slag (GGBFS), Grade 100 or 120 (40 to 50% by weight), or a combination of both. The Class F fly ash (or Class, N pozzolan) should also have a maximum of 1.5% available alkali, a maximum 6% loss on ignition, and a maximum of 8% CaO (lime). A modified ASTM C 1260 using the actual mixture is recommended for ASR testing. In addition to mitigating ASR, these recommendations are expected to: 1) reduced concrete costs; 2) enhance the durability of concrete; 3) increase fly ash and GGBFS recycling; and 4) support the 1997 Kyoto protocol by significantly reducing CO2 production. If 25% of all cement was to be replaced, total savings to the United States economy could be in excess of $1 billion every year.