Synergistic bio-stabilisation of earthen mortar for enhanced mechanical performance

This research examines the mechanical enhancement of earthen mortar through the combined use of cow dung (CD) and sawdust (SD) as biodegradable stabilisers, aiming to develop a structurally reliable and low-carbon alternative to conventional binders. Stabiliser contents ranging from 2.5% to 10% were incorporated into a locally sourced clayey soil, followed by a comprehensive evaluation of fresh and hardened density, unconfined compressive strength, split-tensile strength, flexural capacity, and derived undrained shear strength. The test results show that the CD-SD blend significantly improves mechanical performance, with compressive strength increasing by approximately 40% at 7.5% stabiliser content and tensile strength, and nearly doubling at 10% addition. Flexural strength exhibited a parallel rise of 68% relative to the untreated mix. These improvements are linked to the formation of cementitious reaction products from cow-dung ash, enhanced particle adhesion, and the micro-reinforcing role of SD fibres, which collectively reduce crack formation and increase the material’s resistance to tensile and bending stresses. Concurrently, fresh and hardened densities decreased by 14–21%, producing a lightweight composite without compromising structural reliability. The findings identify an optimum stabiliser range of 7.5–10%, balancing strength enhancement with desirable density reduction. Overall, the study confirms that CD-SD stabilisation provides a feasible, cost-effective, and environmentally responsible approach for improving earthen mortars, offering substantial potential for sustainable construction in regions where low-carbon and locally available materials are essential.