Koichi Matsuzawa

Effects of Exposure Term on the Strength and Elasticity of Concrete Subjected to Elevated Temperature up to 175°C

There are many papers on the effects of high temperature on concrete, but papers about properties of concrete subjected to lower elevated temperature such used in nuclear power plants are still limited. This paper presents the results of experiments conducted to determine the effects of term of exposure to elevated temperatures below the limit for concrete component in nuclear power plants. Sealed cured cylinders made of normal weight concrete containing ordinary portland cement were subjected to temperatures from 20 to 175°C without seal for 10, 30 and 90 days. After exposure, cylinders were tested for weight loss, compressive strength and static modulus of elasticity.

EVALUATION OF THE INFLUENCE OF ACCELERATED CARBONATION ON THE BOND STRENGTH BETWEEN ALC AND CERAMIC TILES

Carbonation of ALC panels progresses simultaneously throughout the whole section. Even with ceramic tiles laid on one side of the panel, ALC is carbonated to the back of the tiles by CO2 penetration from the other side. In this research, tiled ALC panels were subjected to accelerated carbonation followed by bond strength testing between ALC and tiling. As a result, it was found that carbonation of ALC does not directly cause tile spalling up to a carbonation degree of 89%.

Crack-Resistant Properties of Concrete Subjected to Combined Deterioration by Heating and Carbonation

Concrete structures for nuclear power plant may be subjected to the heating action and carbonation action for a long period. Many studies have already reported that the concrete structure subjected to the heating action can be retained by maintaining the heating conditions of not more than 65°C under general control standards for nuclear power plant. The effect of the heating should be considered to discuss the long-term safety and durability of concrete structures in the viewpoint of compressive strength, however the fracture properties of concrete, which were important to discuss the crack resistance for the nuclear power plant, are not yet to be clarified. This paper reports on the investigation into the fracture properties of mortar subjected to the effects of heating and carbonation action. The water-cement ratios (W/Cs) of mortar used in this experiment is set to 0.6, 0.8, 1.0. Mortar specimen size was 40mm x 40 mm x 160 mm. After the 28-day water curing at 20°C, specimens were set in the heating condition of 20°C and 65°C and carbonation acceleration conditions of 0% and 5%. After the heating and carbonation acceleration, three-point bending tests were conducted to measure the load versus crack mouth opening displacement (L-CMOD) curves. The fracture energy was estimated by the tension softening diagram (TSD) calculated by the L-CMOD curve based on the poly-linear inverse analysis. Effects of heating and carbonation on the fracture parameters were discussed.