Alkali-silica reaction and pore solution composition in mortars in sea water

Abstract

The promotion of expansion of mortars containing a reactive aggregate in 1N NaCl solution at 38 °C was attributed to a rise of OH − ion concentration in the pore solution in the mortars. However, it is ambiguous whether the promotion of expansion of mortars in sea water at a room temperature can be explained in the same way as in NaCl solution at an elevated temperature. This study aims at pursuing the expansion behavior of mortars containing a reactive aggregate relating it to their pore solution composition and the extent of alkalisilica reaction occurring within reactive grains. The alkali-silica reaction in mortars in sea water and 0.51N NaCl solution at 20 °C appears to progress differently from that in mortars in 1N NaCl solution at an elevated temperature of 38 °C. The promotion of expansion of mortars in sea water at 20 °C was found to be responsible for an effect of Cl − ions on the alkali-silica reaction at early stages of immersion. Only when OH − ion concentration in the pore solution was relatively high, NaCl and sea water could accelerate the alkali-silica reaction in mortars at 20 °C.