Geotechnical properties of clayey soil improved by sewage sludge ash

Rapid urbanization has resulted in the production of large quantities of sewage sludge over worldwide. The disposal of sewage sludge in landfills or open areas is not considered as an environmentally friendly solution. Therefore, the use of sewage sludge as ash can provide a better solution in geotechnical applications. Keeping this in view, this study investigates the possibility of using sewage sludge ash (SSA) to improve the geotechnical properties of soft clay soil. The sewage sludge ash (SSA) is attained by burning the sludge for 2 h at 900°C. The tests conducted on the clayey soil are specific gravity, standard Proctor test, sieve analysis, Atterberg limits, CBR test and unconfined compression test. Three curing times were used for the untreated soils and soils treated with sewage sludge ash (SSA) which are 3 days, 14 days and 28 days. The sewage sludge ash (SSA) was mixed with the soil at different percentages by weight of the soil at 10%, 15% and 20% of dry soil weight. The results showed that the sludge ash increases the unconfined compressive strength of the soft soil at 3, 14, 28-day curing time. The bearing capacity of the soil decreases after adding SSA at the first, but curing time led to improve the bearing capacity of clayey soil after adding SSA and the percentage of SSA of 10% gave the optimum value of CBR. The results indicated that a better performance of the unconfined shear strength was obtained at 28-day curing time. The findings of this research indicate that sewage sludge ash (SSA) can be used to improve the soft clayey soil and further reduce the environmental risks associated with this substantial.Implications: Rapid urbanization has resulted in the production of large quantities of sewage sludge over worldwide. The disposal of sewage sludge in landfills or open areas is not considered as an environmentally friendly solution. Therefore, the use of sewage sludge as ash can provide a better solution in geotechnical applications. Keeping this in view, this study investigates the possibility of using sewage sludge ash (SSA) to improve geotechnical properties of soft clay soil. In this paper, Sewage Sludge Ash (SSA) is recycled as a new type of chemical addition to soft clay soil and used as a stabilizer to improve a clayey soil. This study proposes that a percent of the total amount of clay to be reinforced is replaced with sewage sludge ash (sewage sludge ash plus soil) in order to achieve the need of improvement in the geotechnical properties of clayey soil and make use of industrial wastes. The sewage sludge ash (SSA) is attained by burning the sludge for 2 h at 900°C. The tests conducted on the clayey soil are specific gravity, standard Proctor test, sieve analysis, Atterberg limits, CBR test, and unconfined compression test. Three curing times were used for the untreated soils and soils treated with sewage sludge ash (SSA) which are 3 days, 14 days, and 28 days. The sludge ash (SSA) was mixed with the soil at different percentages by weight of the soil at 10%, 15%, and 20% of dry soil weight. The results showed that the sludge ash increases the unconfined compression strength of the soft soil at 3, 14, 28-day curing time. The bearing capacity of the soil decreases after adding SSA at the first, but curing time led to improve the bearing capacity of clayey soil after adding SSA and the percentage of SSA of 10% gave the optimum value of CBR. The results indicated that a better performance of the unconfined shear strength was obtained at 28-day curing time. The findings of this research indicate that sewage sludge ash (SSA) can be used to improve the soft clayey soil and further reduce the environmental risks associated with this substantial.