Laboratory Assessment of Strength Development in Concrete Produced with Recycled Demolition Aggregate in Lagos State

Construction and demolition waste in Lagos State generates significant volumes of concrete rubble that are typically landfilled, while virgin aggregate sources face increasing depletion. This study assesses the strength development characteristics of concrete produced using recycled coarse aggregate sourced from demolition sites in Lagos Mainland. Recycled coarse aggregate was collected from three demolition sites in Mushin and Yaba, crushed, and sieved to produce 10 and 20 mm nominal sizes. Physical properties including specific gravity, water absorption, aggregate crushing value, and Los Angeles abrasion value were determined and compared with control natural granite aggregate. Concrete mixes were designed for a target strength of M25, with recycled aggregate replacing natural aggregate at 0, 25, 50, 75, and 100 percent substitution levels. Compressive strength was tested at 7, 14, 28, and 90 days. Results show that recycled aggregate water absorption (5.8 percent) is significantly higher than natural aggregate (0.9 percent), requiring water content adjustment in mix design. At 28 days, compressive strength decreases from 28.4 N/mm2 (control) to 21.6 N/mm2 at 100 percent substitution. Substitution up to 50 percent maintains strength above the M25 specification minimum of 25 N/mm2. The study concludes that up to 50 percent recycled aggregate substitution is appropriate for non-structural applications in Lagos construction, reducing demolition waste landfilling and aggregate demand.

Keywords: recycled aggregate, demolition waste, concrete strength, sustainable construction, Lagos State