コンクリート塊のコンクリート用骨材としての利用に関する研究

Abstract

This study is aimed at clarifying basic properties of concrete using recycled aggregate obtained by crushing from demolished concrete. The concrete waste occurred from concrete struc-tures in Aichi prefecture was used as the material for producing recycled aggregate with a maxi-mum size of 20mm. The demolished concrete was crushed below 40mm by a jaw crusher and not polished in order to do aggregate. Therefore, demolished concrete debris (recycled aggregates) contain impurities (asphalt, and others), and the large amounts of cement paste or mortar adhere to its surface. The concrete made with the recycled fine and coarse aggregate was compared with the concrete used mountain pit sands and sandstone crushed stone aggregates. Aggregates in concrete were replaced the recycled coarse aggregate with sandstone crushed-stone aggregate of 0,30,60 and 100 percent. The concrete by use of the recycled coarse aggregate of 30% had the same good workability and strength as that of natural aggregates concrete. The study also clarified low strength and Young's modulus at 28 days of age, low neutralized depth, high ratios of length change after drying (RH 60%) for 54 weeks. Those results differed by mix proportion from 45 to 65% in water cement ratio.