콘크리트 구성성분 및 함수상태의 변화가 레이저 스캐블링에 미치는 영향

Abstract

It is known that concrete waste accounts for more than 70% of the waste generated during decommissioning of nuclear power plant. A lot of research has been conducted to reduce the amount of concrete waste using mechanical decontamination and chemical decontamination process. However, problems such as safety of the worker, limited accessibility to contaminated area, secondary waste generation, as well as waste disposal and handling have been issued with existing decontamination process. Laser scabbling has been introduced to reduce such problems because it can be used remotely from a long distance to minimize access to radioactively contaminated areas. In this study, the effect of mix proportion and moisture state of concrete on laser scabbling process was investigated. Laser scabbling with 200mm/min scan speed was performed using 5kW fiber laser located 900mm away from the surface of concrete. Weight loss and surface condition of concrete after laser scabbling were evaluated. Compressive strength and void content of concrete were measured, and FE-SEM(Field emission scanning electron microscope) was used for microstructural observation of concrete after laser scabbling. According to the experimental results, high strength concrete with lower void content showed higher removal of concrete after laser scabbling (highest efficiency). The concrete with oven dry state did not show the efficiency for laser scabbling, and, as a result, vitrification has occurred. However, laser scabbling was successfully applied to air dried and saturated surface dried concretes. It was found that the presence of moisture is a necessary prerequisite for laser scabbling of concrete, but moisture content did not seem to significantly affect laser scabbling performance as long as moisture exists in concrete. The effect in the change of the fine aggregate proportion and paste content on laser scabbling was negligible.