Sustainable strength development of construction and demolition waste using water treatment sludge, silica fume, and jute fiber for geopolymer-based pavement subgrades
Mahan Salimi Khoshdel, Hassan Ahmadi Golabkharan, Meghdad Payan, Iman Hosseinpour, Mahyar Arabani, Payam Zanganeh Ranjbar, Mahdi Salimi, Mohammad Mahdi Shalchian
Abstract
• Geotechnical behavior of WTS-SF-based geopolymers with C&D waste was evaluated. • 15% SF and 15% WTS greatly enhanced compressive strength. • 0.75% JF addition raised ITS by 87.5%, improving tensile strength. • JF inclusion increased the soaked CBR value up to 108. • Microstructure showed denser matrices from improved bonding and gel formation. As urbanization accelerates, the unsust disposal of construction and demolition (C&D) waste has become a critical environmental concern. This study presents a novel and sustainable approach to valorizing C&D waste by developing geopolymer-stabilized mixtures incorporating water treatment sludge (WTS), silica fume (SF), and jute fiber (JF). The innovation of this work lies in the synergistic use of multiple industrial by-products within a recycled liquid alkaline activator (RLAA) system, eliminating the need for conventional alkalis while enhancing mechanical and durability properties. Mixtures containing 5–20 wt% WTS and SF and 0.25–1 wt% JF (by weight of dry C&D materials) were evaluated under ambient curing conditions using unconfined compressive strength (UCS), indirect tensile strength (ITS), and California bearing ratio (CBR) tests, supported by microstructural analysis. The optimized blend (15% WTS and 15% SF) achieved a compressive strength of 2.05 MPa, representing a 474.9% improvement over untreated C&D waste, while 0.75% JF increased tensile strength by 87.5% and raised soaked CBR values to 108. Microstructural observations revealed denser matrices and enhanced particle bonding due to geopolymer gel formation and uniform fiber dispersion. These findings highlight the technical feasibility and environmental significance of integrating multiple waste-derived materials into a low-carbon, high-performance stabilization system for sustainable civil infrastructure applications.