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Increasing road construction activities in Nigeria has led to increased demand for lateritic soil (LS), whose properties vary from one location to another, and. The properties of some of this laterite deposits along road alignment can be improved to enable it withstand traffic loads. This paper presents results of the laboratory evaluation of LS stabilised with oil palm fibre ash and cement blends, with a view to determine its suitability as flexible pavement construction material. The mixtures were subjected to British Standard heavy (modified Proctor) compaction energy to determine their strength characteristics. Test results show that the properties of LS improved with oil palm fibre ash and cement treatment. The maximum dry density decreased with corresponding increase in optimum moisture content as the cement content increased from 0% to 6% and the LS content of the mixtures decreased with increased oil palm fibre ash, at a fixed per cent of cement. The peaked California bearing ratio of 190.09% (soaked) recorded for the 80% LS + 14% OPFA + 6% C mix proportion, with 14th day unconfined compressive strength of 785.75 kN/m2, cohesion of 140 kN/m2 and angle of internal friction of 25°, can be used as a base material in road construction. Further work may be encouraged to assess resilient modulus of this material under cyclic load. [ABSTRACT FROM AUTHOR]

An attempt was made to improve the physical and strength properties of a reddish-brown lateritic soil. 15-60% of sand by dry weight of laterite was used as a modifier in the stabilization of the laterite with 3-12% by dry weight of cement. Classification, compaction, California bearing ratio (CBR), and unconfined compressive strength tests were carried out on the specimens. The plasticity index decreased from 17% for untreated laterite to 2.5% when treated with a combination of 60% sand+6% cement. For the two energy levels of compaction, optimum moisture content (OMC) was found to increase with an increase in cement content but decreased as the sand content increased. The OMC at the West African standard (WAS) energy level was consistently lower than the values obtained at the standard proctor (SP) energy level, while the corresponding values of maximum dry density were higher at the WAS energy level than the values at the SP energy level. The CBR requirements for base course material were met when laterite was admixed with 45% sand+6% cement and 30% sand+6% cement, and 15% sand+6% cement, 30% sand+6% cement, and 45% sand+3% cement at the SP and WAS energy levels, respectively. It can be concluded that sand enhanced the effective stabilization of Ikpayongo laterite with cement within the maximum cement content specified by the Nigerian code. [ABSTRACT FROM AUTHOR]