The Utilization of Recycled Concrete Aggregates in Fiber-Reinforced SelfCompacting Concrete

Abstract

– Self-compacting concrete (SCC) is a highly flowable, non-segregating concrete that offers advantages such as faster construction, reduced noise pollution, and improved reinforcement cover and consolidation. However, the production of SCC requires large volumes of powder materials and chemical admixtures, raising environmental concerns. Recycling concrete aggregates (RCA) obtained from construction and demolition waste is a promising approach to enhancing the sustainability of SCC. This study investigates the fresh, mechanical, and durability properties of steel fiber-reinforced SCC incorporating RCA. Crushing leftover concrete from a nearby demolition site and sieving to remove particles larger than 20 mm produced RCA. The SCC mix was designed for a target 28-day compressive strength of 40 MPa with a water-binder ratio of 0.4. Straight steel fibers were added at 0%, 0.5%, 1, 1.5, and 2% by concrete volume to study their reinforcing effects. The SCC mixes utilized Portland cement of the CEM I 42.5 type, with natural aggregates consisting of two granular classes of gravel and natural sand. The superplasticizer was formulated using 30% dry extracts and polycarboxylates as the primary components. Pure, uncontaminated drinking water is used as the mixing water for the production of various SCCs. The results showed that increasing the RCA replacement ratio decreased the workability and mechanical properties of SCC. It became easier to work with, stronger, more flexible, and shrunk less when 0.5% steel fibers were added to 50% RCA. These properties were the same as the control SCC after the addition. The fiber reinforcement compensated for the weaker interfacial transition zone between new cement paste and recycled aggregates.