Mechanical and durability-based life cycle assessment of rice husk ash containing concrete
Parvin Montazeri, Omid Bamshad, Milad Aghililotf, Priyanka Singh
Abstract
The pursuit of sustainable construction materials has intensified interest in rice husk ash (RHA) as a supplementary cementitious material for concrete. However, most previous life cycle assessments (LCAs) have overlooked the combined influence of service life, mechanical performance, and comprehensive system boundaries, resulting in incomplete and biased evaluations of environmental impact. This investigation presents a novel framework for producing RHA concrete grounded in circular economy principles (reduce, reuse, and recycle) and evaluates its sustainability through a comprehensive mechanical and durability-based LCA. For this purpose, a total of twelve concrete mixes were analyzed, featuring varying levels of RHA replacement at 0 %, 10 %, 15 %, and 20 % by weight (wt%) across three water to binder (W/B) ratios (0.35, 0.45, and 0.50). Slump tests were conducted to assess the fresh properties of the mixtures. The hardened properties were evaluated in terms of compressive strength, rapid chloride penetration, rapid chloride migration, and capillary water absorption. Furthermore, the anticipated service life of RHA concrete was estimated utilizing Fick's second law of diffusion. The findings indicated that the incorporation of RHA enhanced both the mechanical strength and durability of concrete, with optimal replacement levels identified between 15 wt% and 20 wt%. This range was specifically chosen because it delivers maximum improvement in compressive strength and durability indicators (notably resistance to chloride penetration and water absorption), which directly translate into significantly extended service life. Importantly, these mechanical and durability benefits coincide with substantial reductions in environmental impacts; for example, replacing 20 wt% of cement with RHA substantially diminished greenhouse gas emissions by 47 %, 73 %, and 82 % in W/B of 0.35, 0.45, and 0.5, respectively, alleviating the environmental burden typically associated with conventional concrete. Thus, the optimal mix, comprising 20 wt% RHA and a W/B ratio of 0.35, not solely by mechanical gains but by the integrated enhancement of both structural performance and environmental sustainability, demonstrating a practical pathway toward greener, longer-lasting concrete.