Geo-engineering Characteristics and Behaviour of Coal-reject Stabilized with Raw-meal.

Abstract

The influence of raw-meal on the geotechnical properties of Nigerian coal-reject was studied and the behavior of the improved material evaluated based on Atterberg limits, linear shrinkage, compaction, California bearing ratio and strength tests. The results of the tests indicate that the liquid limit, plastic limit and plasticity index as well as linear shrinkage values decreased with increasing raw meal content. The results also show that the maximum dry density (MDD) decreased as raw meal content increased up to a maximum of 6% for the modified AASHTO and West African Standard (WAS) compaction energies and 2% raw meal content for BS compaction energy. The California bearing ratio (CBR) attained optimal value at 2% for the modified AASHTO and West African Standard (WAS) compaction energies and 6% raw meal content for BS compaction energy. Peak shear strength was also achieved at 6% raw meal content. These results demonstrate that the geotechnical properties of the coal-reject can be improved significantly with the addition of up to 6% raw meal when compacted at BS compaction energy and 2% raw meal content when compacted at modified AASHTO and WAS compaction energies. A comparison of these results with Nigerian construction specifications shows that the improved material fails to meet specification standards for use as base course material, but meets the standards for use as sub-base material.

Keywords: CBR, Coal-reject, Geotechnical properties