Effects of lithium hydroxide on alkali silica reaction gels created with opal

The reaction of opal with a combined solution of sodium hydroxide and lithium hydroxide was investigated. Sol–Gel Expansion Method was carried to test the expansion capability of ASR gels and SiO2 concentration in the final solution was determined by potassium fluosilicate method to make clear the effect of lithium hydroxide on SiO2 dissolution from opal particles. The results of Sol–Gel Expansion Method suggest that a high dosage level of lithium hydroxide is required to alleviate ASR in a given mix, which is broadly in agreement with those published by other laboratories using other reactive aggregates and tests. The concentration of SiO2 in the final solution indicated that the reaction of alkali with opal was inhibited in the presence of lithium hydroxide. SEM revealed that the morphology of the reaction products was markedly different from those of opal with sodium hydroxide and there was a protective layer on the surface of the reacted opal grains.