Lime Stabilization Effects on Geomechanical Properties of Kombe Mbanga Soils Road Subgrade (Cameroon)

Abstract

Road infrastructure in Cameroon experiences rapid deterioration due to intense seasonal rainfall, high temperatures, and the predominance of weak lateritic soils in tropical environments. These unfavorable conditions reduce pavement performance, increase maintenance costs, and hinder sustainable transportation development, particularly on rural road networks. Soil stabilization using locally available materials has emerged as a cost-effective strategy for improving the engineering properties of these problematic soils. This study evaluates the effectiveness of locally sourced quicklime in enhancing the geotechnical characteristics of lateritic soils collected from the Kombe-Mbanga area in Cameroon and assesses its suitability for road subgrade applications. Ten representative soil samples were collected and characterized through laboratory testing, including particle size distribution, Atterberg limits, Modified Proctor compaction, California Bearing Ratio (CBR), and direct shear strength tests. The tests were performed before and after quicklime stabilization to quantify changes in the soils' mechanical behavior. In addition, statistical analyses were conducted to investigate the relationships between key geotechnical parameters and bearing capacity. The results demonstrate substantial improvements following stabilization. The average CBR increased from 9.04 to 45.08, indicating a significant enhancement in load-bearing capacity. Cohesion increased from 27 to 57 kPa, while the internal friction angle improved from 30° to 57°, reflecting greater shear strength and stability. Statistical analysis further revealed a strong negative correlation between the plasticity index and CBR (r = −0.67), confirming that high plasticity and fine particle content are the primary factors responsible for the poor engineering performance of the untreated soils. These findings demonstrate that locally available quicklime provides a simple, economical, and effective stabilization technique capable of transforming weak tropical lateritic soils into suitable road subgrade materials. The study offers practical guidance for the rehabilitation and construction of durable rural roads in Cameroon and other tropical regions with similar geotechnical and climatic conditions.