Assessment of the Use of Recycled Aggregate in Concrete Production at Building Sites in Osun State

The growing volume of construction demolition waste in Osun State, South West Nigeria, presents an opportunity to use recycled aggregate as a partial replacement for natural aggregate in concrete production, supporting both waste reduction and sustainable construction. This study assessed the availability, properties, and current use of recycled coarse aggregate derived from demolished concrete structures at building sites in Osogbo, Ife, and Ilesha Local Government Areas of Osun State. Recycled aggregate samples were collected from demolition sites, and their physical and mechanical properties (particle size distribution, bulk density, water absorption, and aggregate crushing value) were determined per BS EN 12620:2002. Concrete cubes were cast at recycled aggregate replacement levels of 0%, 25%, 50%, and 100% and tested for compressive strength at 7, 14, and 28 days. Building site surveys (n = 40) assessed awareness and actual usage of recycled aggregate. Results showed that recycled aggregate water absorption (7.4%) and aggregate crushing value (28.3%) were poorer than natural aggregate but within acceptable limits for structural concrete at replacement levels up to 50%. Compressive strength at 50% replacement was 87% of that of 100% natural aggregate concrete at 28 days, meeting NIS 444-1 minimum strength requirements for most residential applications. Recycled aggregate was currently unused at 92% of surveyed sites, primarily due to lack of awareness and concerns about quality. The study recommends a state-level construction waste recycling policy and technical guidance for recycled aggregate use.

Keywords: recycled aggregate, concrete, construction waste, Osun State, sustainable construction