Sustainable Stabilization and Predictive Modeling of Strength Parameters to Improve the Suitability of Tropical Dredged Soils for Low-Cost Infrastructure

Dredged soils are known to have excessively high moisture content, high fines content and low natural strength. These soils require chemical stabilization to become suitable for construction purposes. This paper assesses the stabilization of tropical dredged clay using ordinary Portland cement (OPC), quicklime, and Class F fly ash. Two series of mixtures were prepared: binary mixes with total binder 5%, 10%, and 15% (cement + lime, 1:1 by weight) and ternary mixes with 5% lime, 20% fly ash, and OPC varied at 5%, 10%, and 15%. Specimens were moist cured for 7, 14, and 28 days and tested for unconfined compression (UCS). The 15% OPC mixes achieved the highest strengths (UCS >1000 kPa at 28 days) but failed abruptly. Lime–fly ash blends gained strength gradually and showed ductile post-peak deformation. Strength generally increased with OPC dosage and curing time. Peak strength was obtained at moderate moisture (~35–40%), reflecting a balance between hydration and compaction. Moreover, a predictive model to estimate the Mohr–Coulomb parameters ( c , φ , and E ) was developed. The model successfully uses adjusted empirical correlations to relate UCS to c and φ , and employs standard UCS–modulus relationships for E . The model predictions agreed with literature and the predicted moduli matched known UCS–E correlations - thus, offering a practical alternative to extensive shear testing. The results demonstrate that stabilizing tropical dredged clay with OPC–lime–fly ash can yield material suitability for road bases and subgrades in low-cost infrastructure projects, hence reduce landfilling disposal and save environment.