Soil stabilisation by waste materials has been recently employed to enhance soil engineering properties. The purpose of this study is to compare the impact of utilising sawdust in its raw form versus sawdust ash as a soil stabiliser. This is to determine if sawdust (SD) can be considered as a substitute for sawdust ash (SDA) in order to reduce incineration and air pollution. To fulfil this aim, the Atterberg limits, modified Proctor test, and Direct Shear test were performed on both stabilised and non-stabilised mixtures of clayey soil. The soil was treated with 2%, 5%, 8%, 12%, 15%, and 20% by soil dry weight of both SD and SDA. The findings show that the use of SD and SDA leads to a reduction in the plasticity index and the maximum dry unit weight of the soil while increasing its optimum moisture content. The bearing capacity of the soil was greatest at 5% for both SD and SDA, with SD exhibiting a greater enhancement (31.89%) than SDA. Therefore, it is recommended to utilise SD instead of SDA for soil stabilisation due to its superior effectiveness and less harmful environmental impact.

Rigid and flexible polyurethane foam are recognized for their soil stabilization benefits, backed by substantial research. However, these forms encounter limitations due to expertise and costs. This prompts the investigation of semi-rigid foam, like foam balls, which serves as an efficient waste management technique. Such foams offer practical benefits by seamlessly blending with the soil, reducing time and expenses. This study aims to investigate how semi-rigid foam balls affect the soil compaction and shear characteristics of untreated and cement-treated clayey soils, addressing existing gaps in the literature. Soil samples were tested with foam alone at 5, 10, 15, and 20%, cement alone at 5, 7, 10, and 15%, and a mix of foam and cement. Their compaction and shear behavior were assessed individually and in combinations. Results showed that while cement outperformed foam alone, a 10% cement and 10% foam mix significantly enhanced soil cohesion by 10.13 times and angle of friction by 1.65 times, leading to a 4314.7% increase in bearing capacity. These findings indicate that the semi-rigid foam integrates effectively with the soil and synergistically improves cement stabilization effects. The combination of foam balls and cement presents a promising approach for soil stabilization applications. It offers a cost-effective and practical solution for addressing soil challenges in construction projects.