Corn Husk Ash as an Artificial Supplementary Cementitious Material: A Review

The construction industry’s heavy reliance on traditional cement highlights the need for sustainable supplementary cementitious materials (SCMs). This review synthesises current research on corn husk ash (CHA) an agro-based waste, evaluating its physical, chemical, microstructural, and performance characteristics in mortar, concrete, and soil stabilisation based on relevant standards. Despite the abundance of corn husks, research on CHA as an SCM remains limited. Synthesis of peer-reviewed data indicates that CHA has an average specific gravity of 2.24, a pore volume of 0.08 cc/g, and a Brunauer–Emmett–Teller (BET) surface area of 365.46 m2/g. Key findings indicate that CHA enhances mechanical properties of mortar and concrete at replacement levels of 0–20 wt.% after 56 days of curing. However, the review highlighted an important challenge: workability reduces as replacement level increases, which could be attributed to the high surface area of CHA. Regarding soil stabilisation, the total water absorbed by soil blocks gradually decreased as the CHA content increased, with soil blocks containing 20 wt.% CHA having the lowest water absorption coefficient, 2.65 g/(cm2.min0.5), compared to the reference (46.35 g/(cm2.min0.5) while attaining the highest compressive strength—5.311 MPa—and abrasion resistance—1.823 cm2/g—compared to the reference (4.177 MPa; 0.407 cm2/g). In line with the Environmental Protection Agency (EPA) and United Nations sustainability goals, this review paper proposes that the environmental impact of using CHA via embodied carbon be assessed to determine whether CHA can only carry load or also bear climate responsibility.