Experimental–Data-Driven Assessment of Clayey Soil Stabilization for Pavement Applications Using Chemical and Cementitious Admixtures

Abstract

Geotechnical and pavement uses of clayey subgrade soils are limited due to their low shear strength, high compressibility, poor load-bearing capacity, and moisture sensitivity. Here, 25-grade ordinary Portland cement, 43-grade OPC, 43-grade hydrated lime, 43-grade fly ash (class C), and 43-grade calcium chloride (CaCl₂) have been selected as the individual and selected stabilizers for a brown clayey soil collected from Sulthanpet in Nandi Hobli, Chikkaballapur District in Karnataka, and a like-for-like comparison is made. The tests carried out are the determination of the index property, a standard Proctor compaction test, and unconfined compressive strength tests at 0-, 7-, 14-, and 21-day curing. In every case, the soil response was favorable with an increase in maximum dry density (MDD) and a decrease in optimum moisture content (OMC). Among the additives (when used individually) 4% CaCl₂ produced the highest MDD value of 1.84 g/cm³. The unconfined compressive strength of all treated specimens increased with curing age. In the untreated soil, the maximum UCS was obtained at 21 days which was 3.33 kg/cm² (≈327 kPa) and for 12% CaCl₂, the maximum UCS obtained was 5.64 kg/cm² (≈553 kPa) which is about 69% higher. The composite binder of 10% cement, 15% lime, and 4% CaCl₂ reached 5.08 kg/cm² (≈498 kPa). These improvements are believed to result from cation exchange, flocculation, pore filling, and the progressive formation of cementitious (C–S–H/C–A–H) products that densify the soil fabric and increase interparticle bond strength. Calcium chloride was found to be the most effective single stabilizer, and the cement–lime–CaCl₂ composite was found to be a comparable, possibly more long-lasting alternative. Stabilized soils achieve strength suitable for pavement subgrades, embankments, and shallow foundation projects.