Abstract
While shrinkage reducing admixtures reduce drying shrinkage of concrete, it has been pointed out that the admixture decreases the resistance of concrete to freezing and thawing action. In this investigation, the cause of the decrease of the resistance was examined based on the experiments using three kinds of shrinkage reducing admixtures. As a result, it was suggested that the roughness of pore structure within concrete due to the obstruction of hydration by shrinkage reducing admixtures and the increase in water pressure due to high viscosity of shrinkage reducing admixtures relate to the decrease of the resistance to freezing and thawing. However, an inappropriate air voids system due to small surface tension of shrinkage reducing admixtures has stronger effect on the resistance than these two factors. The large air-void placing factor of concrete using shrinkage reducing admixtures seems to be main factor bringing about the decrease of the resistance. It is necessary to develop the measure making air voids system proper in order to obtain the resistance to freezing and thawing of concrete using shrinkage reducing admixtures.
