Assessing the Impact of Recycled Concrete Aggregates on the Fresh and Hardened Properties of Self-Consolidating Concrete for Structural Precast Applications

This study explores the influence of different concentrations of recycled concrete aggregate (RCA) on the fresh and hardened properties of self-consolidating concrete (SCC) in order to assess the structural suitability of the use of RCA in a precast concrete plant. The study particularly emphasizes the early strength of the produced concrete. The RCA was sourced from crushed concrete used in roadway applications and was sieved to replicate the characteristics of natural aggregate. Five different SCC mixes were produced, with RCA substituting 0%, 10%, 30%, 50%, and 70% of the natural coarse aggregate (NCA) by weight. For each different mix design, the hardened properties tested were the compressive strength and tensile strength. The fresh properties investigated were the passing and filling ability. Additionally, aggregate properties including grain size distribution and absorption of coarse aggregate were studied. The selected mix design follows a typical well-graded self-consolidating concrete mix with 28-day strength of 8000 psi (55.16 MPa). It was found that replacing up to 50% of the NCA with RCA improves the early strength of concrete without a significant impact on the fresh and hardened concrete properties.