Self-compacting concrete with recycled aggregates

Abstract

Nowadays, a large volume of potentially useful crushed construction and demolition wastes is dumped causing environmental problems due to unplanned disposal. One of the potential solutions is the valorization of concrete rubble by using it as a substitute of natural coarse aggregates (NCA) in concrete manufacturing. The usage of Recycled Concrete Aggregate (RCA) in new concrete mixtures has the possibility of reducing the environmental influence and the financial rate with this progressively prominent concrete type. RCA could also be used in new self-compacting concrete (SCC) mixtures. Limited researches investigating the application of coarse recycled concrete aggregates in self-compacting concrete exist. Recycled concrete aggregates should be added in proper amounts since they have a lower density and a higher absorption than natural aggregates. Their effects on the properties of fresh and hardened concrete should be evaluated. The main goal of this project is to determine the optimal replacement ratios of natural coarse aggregates with recycled concrete aggregates in new self-compacting concrete mixtures. RCA were first characterized to determine their physical and mechanical properties. SCC mixtures were then made with different replacement ratios of NCA with RCA: 10%, 15%, 20%, 25% and 30%. The properties of fresh and hardened concrete were determined and compared to those of conventional self-compacting concrete. The fresh concrete test results (J-ring, L-box, slump flow and V-funnel tests) showed that one can make SCC using up to 30% recycled aggregates. The hardened concrete test results (compression strength, indirect tensile strength and flexural strength tests) showed that SCC strength is reduced with the increase of the RCA content. The maximum acceptable replacement ratio of NCA with RCA is 20%.