Effect of water-retaining lightweight aggregate on the reduction of thermal expansion coefficient in mortar subject to temperature histories

Cement paste containing blast furnace slag with a water to binder ratio of 0.40 showed considerable increase in thermal expansion coefficient due to self-desiccation. Hence the control of thermal expansion coefficient by internal curing with light weight aggregate was studied. Three types of fine aggregate, hard sandstone, oven-dry light-weight aggregate (LWA) and water-saturated LWA, and three temperature histories were applied to the mortar specimens with a ground granulated blast furnace slag. Total strains and time-dependent thermal expansion coefficients of the mortar specimens were determined using a newly developed setup comprising a specimen temperature regulator and measuring devices for dimensional change of the specimen. As the experiments of total strain and time-dependent thermal expansion coefficient have shown, the water-saturated LWA was able to control the time-dependent thermal expansion coefficient during the temperature history and could be favorably applied to massive concrete undergoing considerable thermal strain. The effectiveness of water-saturated LWA was found to be valid not only for autogenous shrinkage but also for thermal strain produced by the change in thermal expansion coefficient during the temperature history. These strains have been separated from the total strain by the proposed method.