Applicability of Molten Slag and Porous Ceramic-Roof Tile Waste Aggregate to Massive Structural Concrete

Abstract

The aim of the present study is to investigate the applicability of molten slag derived from municipal waste (MS) and porous ceramic aggregate from roof tile waste (PCA) to massive structural concrete. For this aim, specimens sealed after casting were stored in a temperature-controlled room providing a high temperature history up to the age of 7 days and then at 20 o C. In addition, specimens were also prepared, which were stored at 20 o C after casting. Fine aggregate was replaced with MS at 30vol.% and/or with PCA at 15vol.%. Coarse aggregate was replaced with PCA at 12vol.%. All concretes prepared had a water to cement ratio of 40% and unit water content of 165 kg/m 3. The mechanical properties, shrinkage strain, and shrinkage-induced strain in reinforcement embedded longitudinally in a prismatic specimen were measured. The results showed that compressive strengths of all concretes subjected to the temperature history (Hconcrete) at the age of 28 days were more than 45 N/mm 2 although they were lower than those stored at 20 o C (20-concrete). In addition, the high temperature history increased autogenous shrinkage of concrete without the waste aggregates by 30% at the temperature adjusted age of 150 days. However, the shrinkage in H-concretes containing PCA and/or MS was almost the same as that of 20-concrete without the waste aggregates at the same temperature adjusted age, which means that the PCA and/or MS contributed to mitigating the shrinkage increased by the high temperature history. Besides, reinforcement strain induced by the shrinkage in concrete increased during the temperature rise and decreased during the subsequent temperature drop, and thereafter, increased again under 20 o C. The PCA and MS were effective in reducing the reinforcement strain at the temperature adjusted age of 150 days. Finally, the present waste aggregates have a potential to be applicable to massive structural concrete.