Stabilization of soft clayey soils with sawdust ashes

The problems of soft clayey soils are taken in considerations by many Iraqi geologists and civil engineers, because about 35% of the Iraqi clay soils (especially southern Iraq) are weak. Thus, it is necessary to improve the properties of such soils for road construction by means of using of various stabilizers such as sawdust ash. The main goal of the present study is to stabilize soft clay models with sawdust ash (SDA) additive using different percentages (0, 2, 4, 6, 8 and 10% by dry weight of soil). The results revealed that the additive has adverse effects on the property of soil indices by increasing its liquid limit and plasticity index due to clay content. The mixture of sawdust ashes with soft clay soils improves most other physical and mechanical properties of the soil, as expressed by a general reduction in specific gravity and maximum dry density (MDD), as well as a reduction in the compression coefficients (Ccand Cr) with an increase in SDA content. While increasing the optimum moisture content (OMC) and the undrained shear strength (c(u)) with the increase in SDA content. The stabilized soils (with 4 and 10% ash content) resulted in low CBR values (1.6-1.2%) which can be used as sub-base. The SDA can be considered as a cheap and acceptable stabilizing agent in road construction for improving most of the geotechnical properties of the soft clayey soil.