Use of lithium compounds to prevent expansive alkali?silica reactivity in concrete

The effectiveness of Li2CO3 and LiNO3 in preventing expansive alkali–silica reactivity in concrete mixes made with two natural siliceous aggregates and different alkali contents was investigated using both the expansion test at 38°C and 100% RH and the ultra-accelerated expansion test in alkaline solutions at 150°C. LiNO3 proves to be always effective while Li2CO3 is effective only when the difference between the concrete alkali content (Lac) and the threshold alkali level of the aggregate (TAL) does not exceed 1.7 kg Na2Oeq/m3 and the concrete mixes are stored at 38°C and 100% RH. The ultra-accelerated test methods proves to be appropriate for determining the effective dosages of LiNO3 in concrete mixes made with different alkali contents. There exists a linear relationship between the effective dosage of LiNO3 in terms of Li2O/Na2Oeq molar ratio and the difference Lac-TAL, indicating a remarkable increase of Li2O/Na2Oeq with Lac.