Utilization of recycled ready-mixed concrete waste as fine aggregates in sustainable construction

Abstract

The construction industry is under increasing pressure to adopt sustainable practices due to its heavy reliance on natural resources and significant contribution to environmental degradation. One of the critical issues faced by the concrete sector is the extensive use of river sand as a fine aggregate, which leads to the depletion of natural riverbeds and environmental harm. Simultaneously, the ready-mixed concrete (RMC) industry generates considerable waste, particularly in the form of fresh concrete waste (FCW), which poses disposal and environmental challenges due to its high alkalinity and volume. This research investigates the potential of utilizing recycled ready-mixed concrete waste (RRCW) fines as a partial replacement for river sand in concrete. The study involved experimental testing on the physical properties of RRCW fines, including grading, specific gravity, and water absorption, and compared them with conventional river sand. Concrete mixes were prepared with varying RRCW fines replacement levels (10% to 50%) and evaluated for their fresh properties and 28-day compressive strength. Results showed that RRCW fines possess acceptable gradation but are more porous and absorbent than river sand. The concrete mix with 10% RRCW replacement exhibited the highest compressive strength, outperforming the control mix. Strength gradually decreased beyond 20% replacement, with 50% replacement resulting in the lowest strength. However, up to 30% replacement maintained acceptable strength levels for structural applications. The findings suggest that RRCW fines can be effectively used as a sustainable alternative to river sand, particularly at lower replacement levels. This approach not only supports circular economy principles but also reduces environmental impact and dependence on natural aggregates. The study contributes valuable insight into the technical feasibility of recycling RRCW in concrete production and promotes more sustainable practices in the construction industry.