Granite powder (stone powder), a waste product generated from stone quarries, is increasingly being reused in cement-treated clays. The particle size of stone powders affects the cement-clay reaction by either increasing or reducing the unconfined compressive strength (UCS). This study investigated this phenomenon by separating stone powder from the same batch at the quarry into five particle sizes (A, B, C, D and E: 106–75 µm, 40–75 µm, 20–40 µm, <20 µm and 106– E > C > B > A, which translated into UCS variation in the same order. Stone powders D and E played two roles in UCS development, i.e., nucleation of cementitious products and reaction with Ca(OH)₂ to increase the UCS higher than the control sample. Linear regression equations determined the minimum concentration of amorphous silica for a UCS increment as 9.4 mg/g.

In their activity, termites break down biomass into glucose, forming cementitious compounds. This results in rainfall-resistant mounds for their shelters, which interests the construction industry. This study explored the potential application of the abundant naturally bio-cemented termite mound soils in highway construction. Experimental investigations compared these mound soils to surrounding soils, revealing that mound soils are 68.2% finer in particle size distribution and have 81.4% lower organic content. Atterberg limits indicated 14.6% higher plasticity and a 5.3% increase in specific gravity for mound soils. Atomic absorption spectroscopy showed no significant difference in chemical composition. Proctor tests indicated that the compaction characteristics of the soils were comparable, confirming their engineering viability without modifications. Mound soils exhibited a twofold increase in unconfined compressive strength and a 33.9% increment in California Bearing Ratio strength. One-way analysis of variance tests confirmed these differences with p-value ranges of 0.0056–0.0361 below the 0.05 significance threshold. The study advocates utilising eco-friendly naturally bio-cemented mound soils in highway construction, meeting minimum standards. Mound soils from one acre can construct up to 2,500 m highway, optimising resource use, promoting sustainability by repurposing natural materials, and significantly reducing carbon dioxide emissions. Further research on soil improvement using lignocellulose-degrading enzymes is recommended.

Construction of lightweight foamed cement banking embankments usually requires temporary sites for air-pressure machinery. This study proposes casein, a milk protein, as an additive in cement-treated soils for constructing lightweight embankments to reduce milk waste and the necessity for air pressure machinery. The effects of mixing time, casein content (0%–8%), and cement quantity (100 and 150 kg/m³) on the dry density, unconfined compressive strength, and coefficient of permeability of cement-treated soils were determined. Furthermore, the durability of the cement-treated soils mixed with casein to wet and dry cycles and its impact on the pH of water was determined. It was established that adding 5% of casein to cement-treated soils and mixing for 10 min produced lightweight embankment materials with complaint strength (>300 kPa), durability and permeability (10⁻³ cm/s), minimal environmental impact, and promoted sustainability.