Investigating the mechanical performance of PET fiber-reinforced termite mound soil earth bricks stabilized with cement-rice husk ash binary binders

The escalating demand for cost-effective, lightweight, and resource-efficient construction materials has intensified research into stabilized earth bricks (SEBs) for sustainable housing. This study explores the synergistic potential of three environmental waste materials, termite mound soil (TMS), rice husk ash (RHA), and polyethylene terephthalate (PET) fibers, combined with Portland cement to produce high-performance SEBs. Four mix designs were formulated by keeping cement content constant at 15% and varying TMS (45%-60%), RHA (20%-32%), and PET fibers (5%-8%). Engineering tests were conducted to evaluate physical, chemical, mineralogical, and mechanical properties, including bulk density, water absorption, compressive and flexural strengths, and microstructural analysis. Results identified the PTR-A mix (60% TMS, 20% RHA, 5% PET) as optimal, achieving superior mechanical and durability performance. Bulk density ranged from 1529.55 to 1669.75 kg m⁻³, water absorption from 7.41% to 8.85%, 28-day compressive strength from 3.31 to 11.07 MPa, and flexural strength from 1.57 to 2.68 MPa. Mineralogical analysis revealed dominant phases of calcium hydroxide (CH), calcium silicates (CS), and silica (SiO₂), with C-S-H gel formation indicating strong pozzolanic activity between cement and RHA. While increased RHA and PET content contributed to higher porosity and lower mechanical performance, TMS proved effective in enhancing matrix compactness and strength. Overall, the PET/Cement-RHA/TMS SEBs developed in this study meet relevant performance standards and are suitable for general building applications, particularly for non-load-bearing and interior-use compressed earth bricks. This research highlights a viable path for valorizing agricultural and plastic wastes into sustainable, durable, and affordable construction materials.