This research was carried out with an intention to evaluate the effects of saw dust ash on the geotechnical properties of soil from three locations in Southwestern Nigeria. Tests that were performed on three samples, A, B and C, dealt with consistency limits, specific gravity, compaction, California bearing ratio, unconfined compressive strength and shear strength. These tests were conducted at both non-stabilized and stabilized states by adding 2, 4, 6, 8 and 10% of saw dust ash. The results show that saw dust ash has improved geotechnical properties of the soil samples: maximum dry density increases from 1403 to1456 Kg/m 3 and 1730 to 1785kg/m 3 , optimum moisture content increases from 23.6 to 28.2% and 26.2 to 29.2%, unconfined compressive strength -from 101.4 to 142.14 and 154.97 , shear strength -from 50.92 to 71.07kN/m 2 and 77.49 to 105.99kN/m 2 for samples A and B, respectively. Saw dust ash is therefore found to be an effective stabilizer for lateritic soils.Preface. Road failure is a common problem in Nigeria which is due to low materials application quality in road building. This article has a mission of providing some information to the road building industry that geotechnical properties of the materials they use can be improved by adding a stabilizer such as saw dust ash.

Twenty soil samples collected from the failed portions in the study area were air dried for two weeks before analyses. Each soil samples were subjected to eight engineering tests which include: natural moisture content, atterberg limit, specific gravity, compaction, unconfined compressive strength, California bearing ratio, grain size and hydrometer analysis. Results showed that the natural moisture content ranged from 17.7% to 37.8%, liquid limit from 48.5% to 62.4%, plastic limit from 18.3% to 26.8%, plasticity index from 25.7% to 37.7%, shrinkage limit from 5.8%-12.5%, optimum moisture content from 14.2% to 32.4%, maximum dry density from 1301 Kg/rn3 to 2002 Kg/rn3. Soaked California bearing ratio ranged from 5% to 17%, unsoaked from 15% to 38%, specific gravity from 2.5 to 2.68, unconfined compressive strength r from 112.8 Kpa to 259.7 Kpa, shear strength from 56.4 Kpa to 129.9 Kpa and hydrometer analysis from 48.5% to 72.1%. Based on the Federal Government specifications for pavement construction, for the soil to be suitable, stabilization with bitumen, Portland cement, lime, coal fly ash, and saw dust should be done. Road pavement failure along Arigidi – Oke Agbe road was due to poor engineering geological condition of the sub-grade soils and poor drainage systems.

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