Abstract
The effect of lime pre-treatment duration on some geotechnical properties of shale treated with cement for use as flexible pavement material was studied. Atterberg’s limits, compaction, California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were conducted on the natural shale and shale pre-treated with 0, 3, 6, and 9 % lime and allowed to mellow for 0, 24, and 48 hours, before it was treated with 0, 3, 6 and 9 % cement. Results of tests shows that lime pre treatment mellowing duration greatly enhance the suitability of shale treated with cement. 7 day UCS value of shale increased from 400kN/m 2 to peak value of 2311kN/m 2 when shale pre-treated with 9% lime was allowed to mellow for 48 hours before treatment with 9 % cement. CBR value of natural shale increased from 2.4 % to 112 % when shale pre-treated with 9 % lime and allowed to mellow for 48 hours was treated with 9 % cement. Shale pre-treated with 9 % lime and allowed to mellow for 48 hours before treatment with 6 % cement is recommended for use as road base material in lightly trafficked road and sub-base material of a heavily trafficked road. Keywords: Cement, Lime, Mellow, Pre-treatment, shale
Highlights
Road building in areas and locations characterized with troublesome soil that exhibit swelling and shrinkage has been a major challenge to highway engineers
Based on the observation of the different researchers this study is aimed at extending lime pre-treatment mellowing period to forty-eight hours in the stabilization of shale, a very troublesome soil well known for its swell and shrinkage characteristics with lime and cement
Lime Pre-treatment mellowing duration before treatment with cement enhanced the suitability of shale for use as flexible pavement material
Summary
Road building in areas and locations characterized with troublesome soil that exhibit swelling and shrinkage has been a major challenge to highway engineers. In Makurdi, the capital of Benue state Nigeria, the presence of such soils have resulted in defects such as cracking, rut and excessive heave on pavements. These defects can be attributed to the presence of active clay minerals in such soils. One of the major troublesome soils that is prominent in Makurdi metropolis and other locations in Benue state is shale. O’Flaherty (1974) described shale as essentially a clayey material, which is very likely to break down in the presence of moisture and frost. Abeyesekera et al (1978) described shale as a notoriously unpredictable material, in which a number of failures have been reported involving settlement and shear failure of compacted shale embankments
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