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Journal of the South African Institution of Civil Engineering

On-line version ISSN 2309-8775
Print version ISSN 1021-2019

J. S. Afr. Inst. Civ. Eng. vol.50 n.2 Midrand Jun. 2008




Optimal stabilisation of deltaic laterite



O Omotosho; O J Eze-Uzomaka






Deltaic laterite is the most suitable and most widely used soil material for road embankment in the Niger Delta. Usually, its natural characteristics fall short of the minimum requirements for such applications hence it has to be stabilised to improve its properties. In this study, samples of deltaic lateritic soils were subjected to mechanical (with or without controlled sand addition), cement and cement-sand (composite) stabilisation methods to improve strength for improved engineering applications. Mechanical stabilisation was found to satisfy subgrade requirements while the addition of sand produced sub-base material quality at best depending on compacted maximum dry density (MDD), which itself is dependent on the optimum sand content (OSC). The OSC was also shown to affect the optimum moisture content (OMC) and the soaked California bearing ratio (CBR) of stabilised specimens. Combination of the test results produced a graphical model to predict the influence of mechanical stabilisation on the soil materials using the percentage fines (that is, passing through a 75 urn sieve) obtainable from wet sieving. Cement stabilisation of the soil (by indigenous highway standard) produced base-course quality materials with cement content in excess of 12 %, which is economically unviable. However, the addition of controlled proportions of sharp sand (also abundant in the Niger Delta) to the soil-cement mixtures produced base-course quality materials with 6 % cement (less than half of that obtained through only cement stabilisation) and about 40 % sand content. A model was also presented to predict the other constituents of sand-cement stabilisation using the percentage fines obtainable from wet sieving.

Keywords: deltaic laterites, soilcrete, sand-soilcrete, composite stabilisation, geosta



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Olujide Omotosho
Department of Civil and Environmental Engineering
University of Port Harcourt
Port Harcourt, Nigeria
T +234-803-341-433'

Department of Civil Engineering
University of Nigeria
Nsukka, Nigeria
T +234-803-779-3375




OLUJIDE OMOTOSHO holds a BSc degree in Civil Engineering of the University of Ife (now Obafemi Awolowo University), an MSc degree of the University of Newcastle-upon-Tyne (England) in Geotechnical Engineering, and a PhD degree of the University of Nigeria, Nsukka, also in Geotechnical Engineering. He has made significant contributions to knowledge not only in his area of specialiaation (Geotechnical Engineering) but also in general civil engineering areas. He is senior lecturer and currently the Head of the Department of Civil and Environmental Engineering, University of Port Harcourt, Nigeria.



OJEZE-UZOMAKA is a graduate in Clvil Engineering from the University of Newcastle-upon-Tyne, England, and holds a PhD from the same university. A Fellow of the Nigerian Academy of Engineering, he has published extensively on civil engineering materials and geotechnical engineering. He has leid several Important positions, Including Head, Civil Engineering Department; Dean, Faculty of Engineering; and Dean, School of Postgraduate Studies - all at the University of Nigeria, Nsukka - and Rector, Federal Polytechnic, Owerri. A specialist consultant to several local, national and international organisations, he is also a guest lecturer to the National Institute for Policy and Strategic Studies, Kuru, Nigeria.

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