중성자 차폐능 향상을 위한 붕규산유리 혼입 모르타르의 물리적 특성

Abstract

Concrete has been used successfully as a shielding and structural material in various nuclear-related businesses. High hydrogen content associated with free water (capillary pore solution), physically adsorbed water (within C-S-H layers), and chemically bound water (H in C-S-H structure) in concrete attenuates high energy neutrons effectively. Therefore, the key ingredient for neutron shielding becomes boron compound because it is able to prevent leakage of slow and thermal neutron from concrete. However, addition of boron compound in concrete in a form of borax or boric acid is known to cause severe problems in setting process as well as in strength development. In this research, borosilicate glass was chosen as the source of boron. Since borosilicate glass aggregates are known to have alkali activity, borosilicate glass powder was also incorporated into the mortar, expecting the effect caused by other pozzolanic materials to reduce expansion associated with the alkali silica reaction. X-ray diffraction (XRD), Differential thermal analysis/Thermogravimetric analysis (DTA/TGA), and compressive strength were measured to investigate the pozzolanic activity of borosilicate powder. ASTM C 1260 test procedure was used to investigate the expansion of mortar caused by alkali silica reaction. According to the results of this study, borosilicate glass powder was determined to have pozzolanic activity. In the alkali silica reaction test based on ASTM C 1260, borosilicate glass powder, at 20% replacement with portland cement, certainly suppressed the expansion caused by borosilicate glass aggregate. The 56 day compressive strengths of mortar specimens incorporating both borosilicate glass powder and aggregate were 58∼80% higher compared to those of plain specimens. Such proportion contains B2O3 up to 8.6% (in case of w/c 0.40) in total weight of specimen, and thus determined to be a very strong alternative for neutron shielding mortar formulation.