Time dependent change of thermal expansion coefficient was observed in cement paste with W/B 0.40 whose binder was blast furnace slag cement. This time dependent change of thermal expansion coefficient could make a large amount of shrinkage as a thermal strain during temperature history emulating mass-concrete. In this contribution, control method for thermal expansion coefficient with artificial lightweight aggregate (ALA) was investigated in order to reduce the amount of thermal strain. As a result, saturated or partial saturated ALA could restrain the increment of thermal expansion coefficient compared to that of normal mortar with same W/B, and reduced thermal strain. Autogenous shrinkage of mortar with ALA was also reduced as known in an earlier study, however, greater part of reduction of total strain was result from reduction of thermal strain.
