Ground improvement using waste tyre rubber and recycled aggregates in stone columns

This study explores the development of a sustainable composite system using waste tyre rubber (R) and recycled waste aggregates (WA) from a local Bus Rapid Transit System demolition site for stone column applications. Material characterisation reveals complementary interactions between the rubber matrix and the demolition waste constituents. The research systematically evaluates the shear strength parameters of WA-R composites with rubber contents ranging from 0% to 10% by weight at 2% increments, subsequently evaluating optimal combinations in stone column configurations. Direct shear tests demonstrate progressive enhancement in friction angle (ϕ), with a maximum improvement of 35.54% for the WA8R (8% rubber content) combination, with no measurable cohesion. Load–settlement characteristics obtained using the unit cell concept on soft soil reinforced with a single 25 mm dia. stone column revealed superior load-bearing performance for WA8R columns compared to natural aggregates columns achieving maximum improvement ratios of 5.83 and 5.21 relative to unreinforced soil for spacing-to-diameter (s/d) ratios of 2 and 3, respectively. These findings demonstrate significant potential for sustainable construction practices, especially in applications requiring improved frictional resistance, including retaining wall backfill materials, road sub-base layers, embankments, and ground improvement systems.