Strength Development and Sustainability of Cement-Stabilized Lateritic Soils Modified with Calcium Carbide Residue for Pavement Layers

Portland cement is the most widely used binder for stabilizing lateritic soils in road construction, but its cost and carbon footprint motivate the search for supplementary alkaline wastes. This study evaluated calcium carbide residue (CCR), a by-product of acetylene production, as a partial component of 9% cement-stabilized laterites from Ahoada, Elele-Alimini and Ogbogoro, Rivers State, Nigeria. Particle-size distribution, Atterberg limits, specific gravity, density and compaction characteristics were determined according to AASHTO procedures. Cement-stabilized specimens containing 0, 5, 10, 15, 20, 25 and 30% CCR by weight of the stabilized laterite were cured for 7, 14 and 28 days and tested for unconfined compressive strength (UCS). A strength development index (SDI), referenced to the CCR-free cement-stabilized mixture, quantified the benefit of the by-product. The soils had plasticity indices of 4.2–9.4% and were classified as A-2-4 or A-4 materials. The CCR-free mixtures achieved 28-day UCS values of 1.7–1.9 MPa. Strength increased with CCR content up to an optimum of 15% for all three soils, where 28-day UCS reached 2.8, 3.1 and 2.7 MPa (SDI = 0.65, 0.63 and 0.50) for Alimini, Ogbogoro and Ahoada, respectively. Beyond 20% CCR, strength decreased, and at 30% the 28-day UCS of the Alimini and Ogbogoro mixtures fell below that of the CCR-free mixture. A CCR dosage of 10–20% is therefore recommended for cement-stabilized lateritic subbase and base layers, subject to durability verification.