Assessment of Geotechnical Attributes of Laterites as Sub-base and Sub-Grade Materials in Parts of Northern Anambra Basin Nigeria: Implications for Road Pavement Construction.

Abstract

The suitability of quality sub-base and sub-grade material is crucial for the durability of roads, which in turn drives economic development. Therefore, in this study, we investigates the causes of road pavement failures in the Anyigba region, Nigeria, focusing on the geotechnical and geomorphological characteristics of laterite. The research area, located between 07°21’0” to 07°37’30”N and 07°20’0” to 07°33’0”E, is characterized by fluctuating climatic conditions and varying geomorphological features. Geotechnical sampling and rigorous laboratory analysis were conducted on laterite samples from various locations along the Ajaokuta–Anyigba and Akpa–Anyigba–Dekina roads. Key tests included moisture content, grain size distribution, Atterberg limits, compaction, and California Bearing Ratio (CBR).Results indicated that the laterite samples had moisture contents ranging from 11.4% to 15.9%, and grain size analysis showed sand content between 91.3% and 99.7%, with fines ranging from 0.3% to 8.7%. The Atterberg limits revealed liquid limits between 21.2% and 39.6%, plastic limits between 16.4% and 32.6%, and plasticity indices between 2.5% and 7.9%. Compaction tests showed Maximum Dry Density (MDD) values between 1964 kg/m³ and 2101 kg/m³, and Optimum Moisture Content (OMC) values between 10.7% and 12.4%. CBR tests indicated values from 26% to 66% for unsoaked materials and 13% to 61% for soaked materials. These findings suggest that the laterite in the study area possesses low moisture content and favorable grain size distribution for road construction, with low plasticity and moderate shrinkage resistance. The high MDD and suitable OMC values confirm the material's suitability for sub-base and subgrade applications. CBR values support the adequacy of laterite as a subgrade and sub-base material. This comprehensive analysis highlights the importance of pre-engineering investigations to prevent road failures and contributes to sustainable infrastructure development in the region