Coal production and utilization is associated with the production of waste materials. One of such wastes is coal-reject which is composed of coal fragments, shale, sandstone, siltstone and a host of other rock types. This waste has been studied in Nigeria to determine its engineering properties and potentials for use in engineering construction.Chemical analysis shows that the waste material contains, as its major oxides, silica, alumina, titanium oxide and ferric oxide whereas proximate analysis shows that quartz and clay are the major constituents. The average specific gravity is 1.85. Atterberg limit tests indicate that the clayey fines are of low liquid limit (average 37) and of low-medium plasticity (average PI= 11). Linear shrinkage is as low as 3.9% and suggests the absence of expansive clays in the fines. The maximum dry density (M.D.D.) ranges from 1.35 to 1.59 Mg/m3 while the unsoaked and soaked CBR values range from 11 to 45% and 12–29%, respectively. Shear strength tests gave an angle of shearing resistance of 13–14° with cohesion values of 55–58 kN/m2 while the Los Angeles Abrasion and Aggregate Crushing tests, gave values of 55% and 48%, respectively.Although the material degrades slightly under impact compaction and soaking, the test results suggest that it can be successfully used for a variety of engineering purposes. With careful placement, proper moisture conditioning and compaction, the material would be suitable for highway fills/embankments and sub-bases, unimproved. It cannot, however, be successfully used as base course and structural fills unless improved.
Engineering Geology 06/1991; 30(3-30):337-356. DOI:10.1016/0013-7952(91)90067-U