Effect of type and quantity of inherent alkali cations on alkali-silica reaction

Abstract

In this study, the macroscopical expansion induced by alkali-silica reaction (ASR) and its corresponding ASR products are investigated using ordinary Portland cement (OPC) mortar specimens with a gradient of boosted alkalis. Experimental results show that the expansion increases with the concentration of inherent alkalis. Sodium-boosted samples expand approximately three times as much as potassium-boosted samples. ASR gels that are present in aggregate veins are calcium-free and amorphous; the atomic ratios of ASR gels are nearly independent of the type and quantity of alkali cations. Aggregate ASR gel exudation occurs in high (≥2.5 %) sodium cases and produces potential Na-shlykovite. Crystalline and amorphous calcium-containing ASR products are present in aggregate vicinities in either Na- or K-boosted samples. The higher hydrophilicity of Na-gel in aggregate veins accounts for the larger expansion. Boosted alkali cations are more effective in ASR products formation than in exposing solution. A new observation that NaOH exposure inhibits ASR in K-boosted samples (zero expansion) is reported.