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 38degreesC and 100% RH and the ultra-accelerated expansion test in alkaline solutions at 150degreesC. LiNO3 proves to be always effective while Li2CO3 is effective only when the difference between the concrete alkali content (L-ac) and the threshold alkali level of the aggregate (TAL) does not exceed 1.7 kg Na(2)Oeq/m(3) and the concrete mixes are stored at 38degreesC 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/Na(2)Oeq molar ratio and the difference Lac-TAL, indicating a remarkable increase of Li2O/Na(2)Oeq with L,c.