Mechanical, durability, and thermal performance of bio-stabilized compressed earth blocks for sustainable housing

Affordable and sustainable building materials are urgently needed to address housing shortages in developing nations. Compressed earth blocks (CEBs) are a promising alternative to conventional masonry, yet their mechanical strength and durability remain limiting factors. This study proposes a bio-based stabilization strategy incorporating starch biopolymer (STB, 2–6%) as a binder, wheat husk ash (WHA, 1–3%) as a pozzolanic filler, and NaOH-treated jute fibre (JF, 0.3–0.9%) as reinforcement into sand–clay CEBs. After 56 days of curing, compressive strength increased from 0.41 MPa (untreated) to 4.03 MPa with 4% STB, representing an ∼881% improvement. The addition of 2% WHA further enhanced strength to 4.1 MPa, while incorporation of 0.6% JF raised it to 4.29 MPa, an overall increase of ∼928% compared with untreated blocks. Indirect tensile strength rose from 0.11 MPa to 0.43 MPa (∼289% gain). According to the findings, durability is enhanced in terms of short-term resistance to Freeze–Thaw (F-T) deterioration, with strength loss under 12 F–T cycles reduced from 37% (untreated) to <10% at the optimum mix. Ultrasonic pulse velocity increased by 32% (670.8 to 884.7 m/s), and stiffness rose by 23% (795.5 to 975.6 MPa). Thermal conductivity decreased by up to 18%, improving insulation. Microstructural analyses confirmed hydrogel formation, void filling, and fibre–matrix interlocking as the main mechanisms. Collectively, the STB–WHA–JF composite significantly enhances strength, ductility, durability, and thermal efficiency of CEBs, demonstrating their strong potential as low-cost, eco-friendly, and structurally reliable materials for sustainable building engineering.