The construction industry urgently requires sustainable alternatives to conventional cement to mitigate its environmental footprint, which includes 8% of global CO2 emissions. This review critically examines the potential of rice husk ash (RHA) and silica fume (SF)-industrial and agricultural byproducts-as high-performance supplementary cementitious materials (SCMs) in soil-cement composites. Their pozzolanic reactivity, microstructural enhancement mechanisms, and durability improvements (e.g., compressive strength gains of up to 31.7% for RHA and 250% for SF) are analyzed. This study highlights the synergistic effects of RHA/SF blends in refining pore structure, reducing permeability, and enhancing resistance to chemical attacks. Additionally, this paper quantifies the environmental benefits, including CO2 emission reduction (up to 25% per ton of cement replaced) and resource recovery from agricultural/industrial waste streams. Challenges such as material variability, optimal dosage (10-15% RHA, 5-8% SF), and regulatory barriers are discussed, alongside future directions for scalable adoption. This work aligns with SDGs 9, 11, and 12, offering actionable insights for sustainable material design.
Keywords: circular economy; rice husk ash; silica fume; supplementary cementitious materials; sustainable construction.