원자력 발전소 콘크리트 구조물 깊이별 열화도 평가를 위한 디스크형 콘크리트 시편 적용성

Abstract

The primary aim of this research is to develop a method for assessing depth-specific deterioration of concrete in nuclear power plants using disc-shaped specimens. To assess depth specific deterioration from concrete structure, cylindrical specimens were cut into 10 mm thick disk-shaped specimens to measure the dynamic elastic modulus and split tensile strength of concrete at each depth. The properties of disk-shaped specimens were compared with those of cylindrical specimens, which have been commonly used for diagnosis purposes, to establish a reliable correlation. First set of experimental program was designed to validate the correlation of data obtained from disk and cylindrical specimen. It was found that dynamic elastic modulus obtained from disk specimen was almost identical to that obtained from cylindrical specimen. A correlation between split tensile strength obtained from disk and cylindrical specimen was strong. Dynamic elastic modulus and split tensile strength also showed a strong linear correlation. The results suggest the feasibility of estimating depth specific properties of concrete using disk-shaped specimen. However, the moisture condition of concrete affected dynamic elastic modulus of concrete. Comparing AD (air dry) and SSD (saturated surface dry) conditions, approximately 10% increase in dynamic elastic modulus was observed from disk-shaped specimens. For such reason, data obtained from specimens in AD condition were used to develop estimation formulas that were used to evaluate depth-specific deterioration of concrete. In second set ot experimental program, concrete was exposed to 600°C heat source to induce temperature gradient (to create depth-specific deterioration), cored to produce cylindrical specimen, and cut into disk-specimen. Properties of disk-shaped specimen was measured to evaluate depth specific deterioration in concrete. Results confirmed that the use of disk-shaped specimens for evaluating depth-specific degradation was successfully validated. For a more precise assessment, variations in the dynamic elastic modulus and splitting tensile strength associated with moisture condition, admixture replacement, and the size of the aggregate, needs to be investigated further.