Sustainable Use of Industrial Wastes for Soil Stabilization

Worldwide, large volumes of industrial residues, such as water treatment sludge (WTS), biomass ash (BA), iron slag (IS), and quarry fines (QF), are generated with limited reuse. This study evaluates their potential as additives for two soils, using two types of soils as matrices. A comprehensive laboratory program (particle size distribution, Proctor compaction, Atterberg limits, falling-head permeability, oedometer consolidation, consolidated undrained triaxial tests, and scanning electron microscopy) was performed on soil–residue mixtures across practical dosages. Optimal mixes balanced strength and transport properties: 15% WTS lowered hydraulic conductivity (k) into the 10−9 m/s range while reducing plasticity; 20% BA rendered the soil non-plastic but increased k into the 10−8–10−7 m/s range; 50% IS increased friction angle while maintaining k ~10−8 m/s; and QF produced modest changes while preserving k ~10−9 m/s. These findings support the sustainable reuse of these industrial wastes for soft soil stabilization, also contributing to the circular economy in the industrial and construction sectors, and are aligned with the United Nations’ sustainable development goals 6, 9, 11, 12, and 15.