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 (L_ac) 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 L_ac-TAL, indicating a remarkable increase of Li₂O/Na₂Oeq with L_ac.