Evaluation of Structural Stability by Characterization of Lateritic Soils with Rock Flour along Ibadan-Iwo-Osogbo Highway, Southwestern Nigeria

Abstract

Failures of different categories of roads shortly after being opened to traffic have necessitated the need for sustainable alternative road building materials. This study determines the potential of rock flour on the geotechnical properties of lateritic soils with a view to establish the optimum content of the rock flour required for effective stabilization and proffer lasting remediation measures to the incessant road failures. Ten bulk lateritic soil samples were collected from ten trial pits at depths of 1.5 m in different locations of the study area. Index and engineering property tests were performed on the soils, both in their natural and stabilized states by adding 2, 4, 6, 8 and 10% rock flour contents. In addition, CBR – UCS model was used to establish a third order polynomial to correlate the soil-rock flour mix. The results show that the plasticity and linear shrinkage of the soils decreased with increase in rock flour contents. The MDD of rock flour stabilized soils increase with the maximum improvement observed at 10% by weight of rock flour with the corresponding decrease in OMC. The load bearing capacities (LBC) of the soils increase with the stabilization mix. It was observed that the values meet the requirements for good quality subgrade, subbase materials and some of the soils for base materials in road construction. The results also reveal the improvement of the soil properties. This is further confirmed by the increase in UCS and shear strength of the soils which optimally improved on addition of 8% rock flour. Moreover, the addition of more than 8% by weight of rock flour caused reduction in UCS and shear strength. These results show the stabilizing potentials of rock flour on lateritic soils especially when added at the optimum level. The CBR - UCS models established are in form of third order polynomial (ax3- bx2 + cx +d) with the R2 values, 0.672 and 0.528 which indicate positive correlation of the soil-rock flour mix. Therefore, rock flour can potentially stabilize lateritic soils solely with addition of 8% recommended as an optimum content for stabilizing lateritic soils for road constructions.