Study of Effects of LiNO3 in Alkali-Silica Reaction and Comparison with the Effects of Fly Ash in Reaction

Resumen

Lithium-based additives have shown satisfactory results in the expansion reduction due to alkali-silica reaction (ASR), but many doubts remain about the mechanisms of ASR. The study herein assessed the effects of a lithium nitrate based (LiNO3) chemical addition, using several dosages, in order to understand its expansion mechanisms due to ASR. The study of the effects of the LiNO3 in ASR was conducted by the accelerated mortar bar method (ASTM C-1260), using two kinds of reactivate aggregates, consequently the test lasted up to 30 days. Mortar bars were also molded with a fly ash (FA) based mineral addition to compare the effects of a mineral addition with a chemical one in the expansion due to ASR. The results from the ASTM C-1260 test indicated that the LiNO3 addition was effective in the expansion reduction, but presented different addition values for the acceptable limit of 0.10% at 14 days for each kind of aggregate. It was also observed that mixtures containing LiNO3 reduced the expansion up to 30 days, while for the mixtures containing fly ash the expansion continued to increase throughout the test. The test indicated that the dosages of lithium addition (Li2O/Na2Oeq), efficient in the expansion reduction for the acceptable limit of 0.10% at 14 days, were very high compared to those found in the literature. Folliard et al. (2003), states that the use of cement with a high alkali content (Na2Oeq = 0.9 ± 1.0%) and the modification of the ASTM C-1260, would be the best solution to obtain lithium addition values compatible with filed applications.