Summary
UCLA researchers in the Department of Civil and Environment Engineering have developed a new alkali-silica reaction (ASR) mitigation method using calcium nitrate, which is an abundant, cost-effective alternative to current approaches.
Background
The availability of aggregates for concrete that are not prone to deleterious alkali-silica reaction (ASR) is dwindling, requiring either transportation of non-reactive aggregates over long-distances or chemical methods of mitigation. Current strategies to mitigate ASR rely upon replacement of cement with supplementary cementitious materials (e.g., silica-rich coal fly ashes, slag, metakaolin) or use of chemical admixtures containing lithium. However, the efficacy of these materials is highly variable, due to compositional variation, seasonal supply, or high costs in the case of lithium-based additives.
Innovation
UCLA researchers have demonstrated the use of calcium nitrate (Ca(NO3)2) to mitigate ASR in concrete. The calcium salt is added to the concrete by dissolving it into the water that is used to prepare the mixture (i.e., the combination of cement, supplementary cementitious materials, water, and coarse/fine aggregates). It forms non-expansive calcium-rich reaction products at the interface between the potentially reactive aggregates and the cementitious pore solution within the concrete. This prevents further dissolution of the aggregates, offering an abundant, cost-effective method for ASR inhibition.
Applications
▶ ASR inhibition in concrete materials management and transportation
Advantages
▶ Abundant ingredients
▶ Cost-effective
▶ High efficacy