IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 1 Ver. II (Jan- Feb. 2015), PP 11-14 www.iosrjournals.org DOI: 10.9790/1684-12121114 www.iosrjournals.org 11 | Page Investigation of Geotechnical Properties of a Lateritic Soil with Saw Dust Ash A. O. Ilori 1 , E. A. Udo 2 1 Department of Civil Engineering, University of Uyo, Uyo. Nigeria 2 Department of Civil Engineering, University of Uyo, Uyo. Nigeria Abstract:Saw dust ash (SDA) was investigated as a stabilizing agent for an A-7-6 lateritic soil based on the following engineering properties that directly or indirectly measures the shear strength of a soil.These are,Atterberg limits, Maximum Dry Density (MDD), and 7-day water cured unconfined compressive strength test. With increasing ash content the liquid limit shows a progressive increase up to 8% and then decrease; plastic limit increases up to a value,drops and then levels off; maximum dry density decreases, while optimum moisture content increases. Unconfined compressive strength shows an initial decrease then an increase that reaches a maximum before a drop. Keywords: Lateritic soil,SDA, Stabilization, Unconfined compression Tests, water cured. I. Introduction Laterites are soils which are product of tropical weathering with red or reddish brown or dark brown color with or without nodules or concretions and generally found (but not exclusively) below hardened ferruginous crust or hard pan[1].They are common residual tropical soil often used in road construction either as a subgrade, sub-base or base material. When use in this form it may be necessary to improve its geotechnical properties to achieve the desired shear strength. The usual method of doing this is the use of admixtures such asPortland cement, bituminous materials among others. It is often not economical to employ these admixtures in minor trafficked roads. Basic waste materials from industries are sometimes employed to offset cost. Waste materials such as rice husk ash (RHA) either alone or in mixture with lime has been employed for soil stabilization [2], [3], respectively. Other materials include saw dusts in its burnt form (saw dust ash-SDA). Its possible use as a stabilizing material is investigated in this study II. Study Objectives The study aims to determine the suitability of ash from saw dust as a stabilizing material. To achieve this it must be able to improve the strength property of soil and retain such in the field. The first aspect deals with strength of improved soil without any special treatment, while the second aspect deals with the problem of strength with age. Both are investigated in this study. III. Materials And Method The soil used was a lateritic soil collected from a building site in Obafemi Awolowo University. Ile Ife, Nigeria. The natural moisture content, Atterberg limits, Sieve analysis (mechanical and Hydrometer), Maximum dry density tests using standard proctor were carried on the native soil. These initial experiments were for classification purposes that will lead to evaluation of rating of the soil for highway construction purposes. Saw dust was collected from a saw millby name Lambua Wood Industry Limitedalso in Ile –ife; and were burnt with a metal drum which has a removable circular pipe of 7.5 cm diameter placed in the center of the drum. The drum has a diameter of 0.8 m and 1.2 m in height; with perforated nail size holes beneath it. The saw dust were packed in the drum around the circular pipe. The pipe was removed before burning commences. The arrangement allows for efficient burning of the saw dust.The burnt product was sieve through a sieve no. 40 to remove the carbon particles which are known to be deleterious to soil strength [4]. Samples of the native soil were then mixed with 2%, 6%, 8%, 12%, 16% and 20% by weight of saw dust ash, the resulting samples were water cured for 7 days; and Atterberg limits, standard proctor compaction tests, Unconfined compression tests were performed on each of samples with the different percentages of saw dust ash mentioned above, by first carrying out compaction test at optimum moisture established for the different percentages of saw dust ash(SDA). IV. Results And Discussion 4.1 Soil classification and soil subgrade rating The native soil is classified using the American Association of State and Highways Transportation Officials (AASHTO) classification as an A-7-6 soil with Group Index Value (GI) of 8. Fig. 1 shows the grain