The influence of alkali-silica reaction (ASR) gel composition on its hydrophilic properties and free swelling in contact with water vapor

Synthetic ASR gels with 20 different chemical compositions similar to those found in field concretes were produced, and the effects of composition (i.e., Ca/Si, Na/Si and K/Si) on their hydrophilic and swelling behavior were investigated. Minibar gel specimens were cast and tested for time dependent measurement of the free swelling strain and weight change of the gels when exposed to 95% RH. The equilibrium relative humidity (ERH) of the gels was also measured for assessing their hydrophilic potential. The results suggest that higher Na/Si and K/Si increase the free swelling and water absorption of the gels, and reduce their ERH. Ca/Si showed a multi-episode effect on the swelling and water absorption of the gels, while showing no significant effect on their ERH. Discussions on the observed effects are provided and regression models for predicting the swelling and hydrophilic properties of the gels are developed.