In recent years, alkali–silica reaction (ASR) has been found to be responsible for much of the premature deterioration of many concrete structures in the Pakistan,India,United States and other countries throughout the world; consequently, there has been renewed interest in using lithium compounds (lithium hydroxide, lithium carbonate, and lithium nitrate) to combat this deleterious chemical reaction. The most promising of these lithium compounds is a solution of lithium nitrate. Research efforts are increasingly focused on understanding the mechanism by which lithium materials inhibit alkali–silica reaction. Furthermore, work continues toward improving the cost effectiveness of this mitigation strategy.
Concrete containing reactive aggregates can experience abnormal internal expansion and cracking due to alkali-silica reaction (ASR). As low alkali cements and good quality, non-reactive aggregates become more difficult to find, ASR is becoming more of a durability issue. ASR is a two-step reaction between dissolved alkalis (sodium and potassium) in concrete and reactive siliceous aggregates.
Step 1: The chemical reaction between the reactive silica in the siliceous aggregate and the alkali present in concrete to produce an alkali-silica gel.
Step 2: Expansion (swelling) of the alkali-silica gel when it comes in contact with moisture that creates internal pressures within the concrete. Visible symptoms of ASR include expansion-induced map cracking and the exudation of a white gel.