Proper Mix Proportion and Construction Method of Waste Concrete Using Recycled Coarse Aggregate in Site Considering Environment

Abstract

When the concrete waste is recycled as the aggregate, the concrete waste is generally carried to the plant and the recycled aggregate is manufactured. However, in this method it needs significantly much energy and causes much CO₂ when the concrete waste is carried to the plant. Therefore, it is need to consider about environment to study on recycling of concrete waste in site. In this study, it is investigated, appropriate mix proportions used recycled coarse aggregate, properties of fresh concrete, pumpability, and properties of hardened concrete in case recycling of concrete waste in site, and when the mortar is brought to the site and the recycled coarse aggregate in the dry state is used, the recycled coarse aggregate is put into the mortar in which the amount of water corresponding to the water absorption rate of the recycled coarse aggregate in the dry state is corrected, it is discussed the freshness and curability of the concrete produced in the above, as well as the aging and pumping properties of the slump. From the scope of this study, when the mortar is brought into the site and the recycled coarse aggregate in an air-dried state is put in the site, if the amount of water corresponding to the effective water absorption rate of the regenerated coarse aggregate is corrected at the mortar manufacturing stage, the compressive strength and tensile strength, the static elastic modulus and the chloride ion penetration depth were about the same as when the recycled coarse aggregate in the surface dry state was used. In addition, it is considered that the same degree of fluidity as when the recycled coarse aggregate in the surface dry state is used even after pumping.