ABSTRACT
Stabilization of soil is a practice which is widely used in road construction to improve the engineering properties of natural soils. A lot of industrially manufactured materials like cement, lime, bitumen, fly ash, quarry dust, have been added to lateritic soils to improve its geotechnical properties. Based on the high cost and less availability of these materials, there is need to go into research on how to discover new materials that will be readily available at cheaper cost which will be used as good stabilizing agents and have positive impact on the geotechnical properties of lateritic soils. This research therefore, is aimed at using lime and rice husk ash separately and combined in varying proportions at different percentage mix in stabilizing lateritic soil for use as sub-base materials in road construction.
Soil samples were collected from two burrow pits. One located at Upper Siluko by Iguoriakhi village in Ovia North East Local Government Area of Edo State and the other along Benin Abraka Road at Evbuehia village in Orhionmwon Local Government Area of Edo State, Nigeria. The soil was collected and transported in sack bags to the University of Benin Geotechnical Engineering Laboratory, where the following tests were carried out; Specific gravity, Gradation test (Sieve Analysis), Atterberg Limit, Natural Moisture Content, Proctor compaction, and California Bearing Ratio test, using the British Standard Specifications (B.S 1377: 1975).
Two stabilizing agents were used on both soils. Each and a combination of both stabilizers was added at 0, 4, 8, 12 and 16% replacement levels respectively with 100% RHA mix, 100% lime mix, 70% RHA + 30% lime mix, 30% RHA + 70% lime mix and 50% RHA + 50% lime mix ratio with the soil. Statistical model analysis revealed that lime is the best stabilizer, relative to RHA, to be used for soil improvement giving a peak CBR value of 59.84 at 12% stabilization for Iguoriakhi lateritic soil and 30.06% at 16% stabilization for Evbuehia lateritic soil after 24 hours of soaking. Owning to the specification stated by the Federal Ministry of Works and Housing for road work construction (1997) Clause 6201, soil with these CBR values is fit for use as sub-base material in road construction. Statistical analysis also suggests Lime:RHA of 7:3 and 1:0 at concentration of 240g in 3000g of bulk soil as the highest level of Iguoriakhi lateritic soil improvement with Lime:RHA preferably 1:0 and mix ratio of Lime:RHA at 7:3 as the most effective for Evbuehia soil improvement but this becomes ineffective at concentration of 240g in soil, indicating that Lime-RHA mixture are not strong enough to achieve proper improvement in the soil.
