Soil erosion, a global problem, degrades land quality and increases pollution and sedimentation in bodies of water. This study propounds a new material to mitigate soil erosion using rice straw-based polyurethane foam (RSPF) blocks as a potential replacement for commercially available expanded polystyrene (EPS) foam in slope stabilization. RSPF was synthesized via a conventional one-shot foaming method with 15% rice straw-based polyol content. The RSPF blocks have an average density of 43.29 kg/m³, average compressive strength of 184.55 kPa, closed cell content of 88.4%, and water absorption capacity of 262% that can effectively reduce water runoff. These properties are comparable to EPS foams according to ASTM D6817, except for the high absorption capacity of RSPF. This added feature allows the foam to act as topsoil protection by reducing runoff. In slope stabilization and topsoil protection applications, the effectiveness of the RSPF blocks in reducing soil loss was tested in both simulated and natural rainfall events with different land slope degrees, rain intensities, and soil covers. Results show that the use of RSPF in the simulated setup with a heavy rain intensity of 80 mm/h reduced the soil loss by 61.5%, 22.7%, and 4.3% in 5°, 10°, and 20° of land slope, respectively. There was also a higher degree of soil loss reduction when the RSPF block was coupled with a natural vegetation soil cover by 79.6%, 70%, and 19.3% in 5°, 10°, and 20° land slopes, respectively. Moreover, in the natural rainfall events in an open field with a land slope of 20°, the recorded soil loss reduction reached 93.6–98.8% at an average rainfall intensity of 16.26 mm/h. Additionally, the relationship between soil loss and land slope was investigated to produce a best fit model that predicts the soil loss up to a 20° land slope. An interesting observation was made wherein the erosion rate increased using linear regression modeling in the simulated setup for bare soil (BS), soil with vegetation (SV), soil with RSPF (SF), and soil with RSPF and vegetation (FV), with high coefficient of determination (R²) values between 0.92 and 0.99. These findings suggest that the RSPF block is a promising alternative and sustainable material for EPS foams in mitigating soil erosion, especially under heavy rainfall conditions.

This state-of-the-art review synthesizes recent advances in soil stabilization using calcium carbide residue (CCR) combined with selected industrial by-products, including fly ash, lime, rice husk ash (RHA), and polypropylene fibers, with a focus on applications in road engineering. While CCR alone can improve unconfined compressive strength (UCS) to approximately 0.5 MPa at 28 days, its performance is often constrained by shrinkage cracking, moisture sensitivity, and potential environmental concerns. The reviewed literature indicates that hybrid CCR-based systems can substantially enhance mechanical performance and durability: CCR–fly ash blends have been reported to achieve UCS values exceeding 3.0 MPa with high strength retention under wet–dry cycling; CCR–RHA mixtures significantly reduce swelling potential; and fiber-reinforced formulations improve tensile resistance and crack control under dynamic loading. These performance trends are commonly attributed to combined effects associated with pozzolanic reactions forming calcium silicate and aluminate hydrates (C–S–H and C–A–H), matrix densification, and fiber-induced crack-bridging mechanisms, although quantitative isolation of individual component contributions remains limited in existing studies. The review further highlights performance-oriented mix design strategies, microstructural characterization approaches (e.g. SEM and XRD), and curing considerations relevant to long-term stability. Emerging data-driven and machine-learning-based predictive models are also discussed as promising tools for optimizing CCR-based formulations across diverse soil types and climatic conditions. Overall, CCR-based composite stabilization systems demonstrate strong potential as sustainable alternatives to conventional cement–lime treatments, consistent with circular economy principles, while continued field validation and long-term assessment remain essential for widespread implementation.