Influence of bond strength in treated mixed recycled aggregate concrete incorporating olivine sand.

The growing need for sustainable construction materials has driven significant efforts to reduce dependence on virgin raw materials and minimize construction and demolition (C&D) waste. In this context, recycled aggregates and alternative fillers have emerged as promising substitutes to conventional materials, contributing to environmental sustainability while enhancing concrete performance. This study investigates the influence of bond strength in three distinct concrete mixes: Mixed Recycled Aggregate (MRA) concrete, Treated Mixed Recycled Aggregate (TMRA) concrete, and TMRA incorporating Olivine Sand (TMRAOS) concrete. Experimental analyses, including compressive strength, pull-out tests and microstructural evaluations using HRSEM, revealed that the incorporation of treated MRA and Olivine Sand significantly enhanced the bond strength at the rebar-concrete interface. The TMRAOS mix exhibited superior mechanical strength, showing improvements of 28.55% and 11.90% compared to MRA and TMRA mixes, respectively. In terms of bond performance, bond strength increased from 4.48 to 5.85 MPa in MRA to 6.11-8.05 MPa in TMRA, and further to 6.35-8.67 MPa in TMRAOS, with corresponding slip values of 2.48-4.36, 2.75-4.87, and 2.96-5.23 mm, respectively. It also demonstrated improved stress distribution, reduced crack propagation, and enhanced bond-slip behaviour. Finite element modelling (FEM) further validated these findings, showing strong agreement between experimental and numerical results. This study highlights TMRAOS concrete as an eco-friendly and structurally efficient alternative to conventional concrete, with strong potential for sustainable infrastructure applications.