Development of Processing Methods to Improve Strength of Concrete with 100% Recycled Coarse Aggregate

Abstract

Because of the increasing difficulty in obtaining natural aggregate, alternative aggregates have been considered in the construction industry. One of the feasible alternatives is to reuse construction and demolition waste as aggregates, called recycled aggregate, to make new concrete called recycled aggregate concrete (RAC). However, the compressive strength of RAC is usually poor due primarily to the high water absorption capacity, high porosity, and weaker bond of interfacial transition zone between recycled aggregate and new cement mortar. This paper presents the results of a comprehensive experimental study on RACs made of 100% recycled coarse aggregate. Three different mixing approaches, several surface pretreatment methods with two different pretreatment materials were used to improve the compressive strength of RAC. The experimental results showed that proper surface pretreatments and mixing approaches can improve the quality of RAC significantly. The water-cement ratio of pretreatment materials is very important. The compressive strength of an optimized RAC with 100% recycled coarse aggregate can reach as high as 43.3 MPa (6,277 psi) on 28 days.