EFFECTS OF DEMOLDING AGE ON THE STRENGTH DEVELOPMENT AND THE CARBONATION RESISTANCE OF LOW-HEAT PORTLAND CEMENT FLY ASH SYSTEM MATERIALS, AND NONDESTRUCTIVE EVALUATIONS OF THEIR SURFACE QUALITIES

Abstract

The effects of demolding age on the strength development and the carbonation resistance of low-heat Portland cement fly ash system materials, which have been researched as a candidate material for low-level radioactive waste disposal in Japan, were experimentally examined with the aim of optimizing the curing condition for them. The results show that the longer term until demolding in age from 7 to 28 days is set up, the more the compressive strength and static modulus of elasticity increase. It is found that, in carbonation acceleration tests, the carbonation rates of demolded specimens at 28-day age are reduced by half value of demolded specimens at 7-day age. In addition, it is clarified that the values of nondestructive-measured surface air permeability of specimens correlate to their carbonation rates and surface permeability test may be useful as a method for the inspection of surface quality of casted concrete with low-heat Portland cement fly ash system materials.