Mechanical characterization of recycled concrete under various aggregate replacement scenarios

Abstract

Due to limited availability of concrete sources, recycled concrete is gaining more attention. Virtually all studies on recycled concrete have focused on independent use of recycled aggregates. Limited experimental tests have been done considering simultaneous incorporation of recycled coarse and fine aggregates to prepare normal strength concrete. The replacement interval of recycled aggregates is generally large, not systematic, and the two-stage mixing approach, in conjunction with the water compensation method, is not widely explored. This paper investigates the influence of recycled coarse and fine aggregates on the strength and workability of normal strength concrete using two-stage mixing method. The study is carried out in two phases. The first includes independent replacements of coarse and fine aggregates at 5% replacement increment rate and the second phase comprises simultaneous replacements of both based on previous results. A new approach to estimate additional water for recycled coarse aggregate is proposed and used effectively. Optimum use and maximum favorable extents of recycled coarse aggregate are estimated to be 25% and up to 40% and that for recycled fine aggregate are found to be 30% and up to 50%. The simultaneous use of recycled coarse fine aggregates at various proportions for 55% replacement of total aggregates highlighted the greatest strengths among the tested scenarios. The sum of the findings highlights that simultaneous replacement of coarse and fine aggregates using recycled aggregates from concrete waste can assure adequate strength and can be used as a sustainable solution. We also propose correlations for splitting tensile strength and compressive strength for recycled concrete.