Preliminary evaluation of treated bio-residue as a modifier for bitumen

Abstract

With the global shift toward sustainable construction practices, the reuse of organic industrial by-products in pavement applications is gaining momentum. Bio-residues, when appropriately treated, can serve as eco-friendly alternatives to conventional binders. This study presents a preliminary investigation into the use of thermally treated Caffeine Spent Residue (CSR) as a partial replacement for bitumen in binder formulations. The CSR, derived from organic industrial waste, underwent thermal pretreatment to improve compatibility with the bituminous phase. The treated CSR was then mixed with bitumen (VG-40) by replacing it at varying levels—0 %, 3 %, 6 %, 9 %, 12 %, and 15 % by weight using a laboratory-scale high-shear mixer to produce Bio-residue Modified Bitumen (BRMB). The resulting BRMB samples were evaluated through penetration and softening point tests, along with rheological characterization using the Superpave rutting parameter (G?/sin ?) to assess the influence of treated CSR on fundamental binder properties. Both unaged and RTFO-aged samples were analyzed to capture the impact of short-term ageing on consistency and rutting resistance. Additionally, a cradle-to-gate assessment of embodied energy (EE) and embodied carbon (EC) revealed that replacing 10 % of bitumen with treated CSR significantly reduced the energy consumption and carbon emissions per kilogram of binder. The findings establish that treated CSR, particularly at a 9–10 % replacement level, offers a promising pathway for enhancing the sustainability of bituminous binders. © 2025 Elsevier B.V.