An Appraissal of the Performance of Geosta as a Stabilising Agent for Deltaic Laterite in Sub-Base Construction |
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Authors: | Olujide Omotosho O J Eze-Uzomaka |
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Institution: | (1) Civil & Environmental Engineering Department, University of Port Harcourt, Port Harcourt, Nigeria;(2) Civil Engineering Department, University of Nigeria, Nsukka, Nigeria |
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Abstract: | This study was prompted by the massive and unprecedented failure experienced within a very short time after construction of
“Ada-George Road” which had deltaic lateritic sub-base stabilised with undisclosed but most probably uncontrolled (scientifically) proportions
of cement and geosta (a relatively new chemical stabiliser). Samples of the deltaic laterite were taken from two of the borrow-pits
within Port Harcourt metropolis from which materials were quarried for the construction of the sub-base. The results showed
that although geosta addition to deltaic laterite mixed with cement gives considerable improvement on the strength of the
resulting mixture, this stabilisation is only effective at very low geosta content not exceeding 2% depending on the optimum geosta content (OGC) which in turn is a function of the percentage of fines of the soil. But the Ada George road project appeared to be politically
rather than scientifically motivated. Consequently, the OGC must have been grossly exceeded in the construction of this geosta
stabilised sub-base. As a result, the as-built CBR must have been much lower than expected hence the massive failure that
resulted. Even for 2% geosta content, this composite stabilisation was also found to be most effective at 4% cement content. |
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Keywords: | Deltaic laterite Geosta Niger delta Stabilisation Sub-base |
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