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Recently, the cracks of concrete by drying shrinkage become one of the problems in the construction industry in Japan. The drying shrinkage decreases when the concrete is produced with limestone aggregate. However, it is not clear why the drying shrinkage is decreased. The purpose of this study is to clarify the relation between the drying shrinkage of concrete and the limestone aggregate. In this study, the experiments about the strength, elasticity and drying shrinkage of concrete and the physical properties and shrinkage of coarse aggregates were conducted. It is thought that the volume change of aggregates affects directly the drying shrinkage in concrete.

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The raw materials from household garbage and industrial waste have increased its usage in the concrete and cement industries. These eco-materials have helped the environment, avoiding pollution, land filling or burning of waste and the usage of other natural resources. However, the cost of many eco-materials is still higher than that of common natural materials. It is necessary to study in detail its behavior and properties to decrease its cost and increase its performance. This research deals with Eco-cement and molten slag aggregate which main raw materials are household garbage and industrial waste. Concretes produced with Portland cement and Eco-cement were mixed with gravel, limestone, quartz and molten slag aggregates to compare its properties. The fracture energy, strength and modulus of elasticity tests were performed and discussed in this paper. The concretes produced with Eco-cement and molten slag aggregate show better results than those produced with Portland cement and natural aggregates.

This study was carried out to examine the application of sewage sludge molten slag as coarse aggregate for concrete and the influence of the quality of molten slag on the mechanical properties of concrete. As a result, it was clarified that the mechanical properties of concrete by using molten slag coarse aggregate depended on the quality of molten slag. The concrete by using molten slag coarse aggregate which was good strength had performance equivalent to normal aggregate concrete. In the quality standard of molten slag for concrete, it is necessary to provide not only the density and water absorption but also the standard related to the strength of aggregate.