Effect of Calcium-Sodium Carbonate Mixture on Geotechnical Properties of Laterite Soil for Road Applications
1* Adedokun, S. I., 1 Chukwuma, J. E., 1Olagunju, B. Y., 2Ayanlere, S. A. and 1 Nwaobasi, C. A.
1Civil and Environmental Engineering, University of Lagos, Lagos, Lagos State, Nigeria.
2 Civil Engineering, LAUTECH, Ogbomoso, Oyo State, Nigeria
DOI: 10.36108/laujoces/6202.61.0271
Abstract
Laterite soils have been found to exhibit swelling-shrinkage behaviours whenever there are seasonal and environmental changes. These phenomena negatively affect the strength and stability of the soil. Consequently, this study investigated the effect of calcium carbonate (CaCO₃) and sodium carbonate (Na₂CO₃) mixtures, at ratios of 1:1 and 3:1 (CaCO₃:Na₂CO₃), in stabilizing a tropical laterite soil. Stabilization was carried out at additive contents of 0 – 10% (at 2.5% incremental interval) by dry weight of soil sample. Consistency limits, compaction [West African Standard (WAS) and British Standard Light (BSL)] and California Bearing Ratio (CBR) tests were carried out to assess the impact of stabilization on compaction characteristics and strength performance. Results showed that Plasticity Index (PI) reduced from 16.9-5.3% and 16.9-0.40% as the carbonate dosage increased from 0-10% under the 1:1 and 3:1 carbonate ratios, respectively, indicating reduced swelling potential and enhanced workability. The Optimum Moisture Content (OMC) declined while the Maximum Dry Density (MDD) for WAS rose from 1.72-1.78 g/cm3 and 1.72-1.81 g/cm3 with increasing carbonate treatment up to 7.5% under 1:1 and 3:1, respectively. Similarly, the corresponding WAS soaked CBR values increased from 20.4-37.6% and 20.4- 49.0% with increasing stabilizer content from 0-7.5%, transforming the soil from weak subgrade to a material meeting Nigerian specifications for sub-base applications (CBR > 30%). These results revealed that 3:1 mix ratio consistently outperformed the 1:1 mixture. The outcome also indicated that the combined use of CaCO₃ and Na₂CO₃, up to 7.5%, improved the properties of laterite soil, thereby enhancing its suitability for pavement construction.
Keywords: Calcium carbonate, Geotechnical properties, Laterite soil, Sodium carbonate