Sustainable Stabilization of Expansive Soil Using Industrial By-Products and Bio-Based Additives

Expansive soils undergo pronounced swell–shrink deformation with seasonal moisture variation, creating differential heave, loss of bearing capacity, pavement distortion, and foundation distress. Conventional lime and Portland-cement stabilization is effective, but its embodied-energy and carbon burden has accelerated interest in circular and bio-derived alternatives. This paper presents an IEEE-style critical synthesis and proposed experimental framework for stabilizing expansive soil using industrial by-products—principally fly ash, ground-granulated blast-furnace slag (GGBS), steel slag, rice-husk ash, and related mineral residues—together with bio-based additives such as xanthan gum, guar gum, and lignin. Published evidence indicates that fly ash dosages in the range of 25–40% can substantially improve plasticity, strength, penetration resistance, swell behavior, and compressibility, while FA–GGBS systems provide additional latent-hydraulic and geopolymeric bonding. Biopolymers act through hydrogel formation, hydrogen bonding, pore filling, and particle bridging, offering a complementary mechanism to inorganic cementation. The manuscript develops a hybrid stabilization hypothesis in which an industrial binder supplies durable mineral bonding and a low-dose biopolymer improves early cohesion, moisture resistance, and particle connectivity. A structured testing program is proposed covering Atterberg limits, compaction, free swell/swell pressure, unconfined compressive strength (UCS), California Bearing Ratio (CBR), wet–dry durability, microstructure, and environmental screening. Equations, literature-derived performance graphs, comparative tables, and a multi-criteria sustainability index are included. The synthesis identifies curing regime, binder chemistry, biopolymer dosage, durability, and leachability as the principal variables that must be resolved before large-scale field adoption.