Abstract

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This study was aimed at the evaluation of the stabilization potential of sawdust ash (SDA) on black cotton soil. Soil samples were treated with up to 10 % SDA content by dry weight of soil compacted with reduced British Standard light (RBSL) energy. Index properties of the natural soil showed that the soil belongs to A-7-5 (36) in American Association of State Highway Transportation Officials (AASHTO) classification system and CH in Unified Soil Classification System (USCS) classification system. The natural soil has liquid limit, plasticity index and free swell values of 60.0, 32.4 and 50.0 %, respectively. These properties suggest a soil that cannot be used for engineering purpose in its natural state and requires improvement. The liquid limit, plastic limit and linear shrinkage decreased to minimum values of 54 %, 24.4 %, and 14.2 %, respectively, while plasticity index increased to 14.2 % at 10 % SDA content. Also optimum moisture content (OMC) increased to a maximum value of 30 % while maximum dry density decreased to a minimum value of 0.86Mg/m3 at 10 % SDA content. Peak unsoaked California bearing ratio (CBR) value of 4 % was recorded at 2% SDA content. On the other hand peak 7 days unconfined compressive strength (UCS) value of 90kN/m2 was recorded at 8 % SDA content. This value fell of specification requirement of the CBR value to be used as sub-base or base material. The durability of samples determined by immersion in water recorded peak resistance to loss in strength of 48.24 % (i.e., loss in strength of 51.76 %) at 8 % SDA content. The results recorded indicate that black cotton soil compacted with RBSL energy cannot be used as a road pavement material, but for low load bearing structures such as road shoulders and pedestrian walkways. However, SDA can be beneficially used as an admixture in road construction when a higher compactive effort is used.

Keywords: Black cotton soil, Saw dust ash, Stabilization, Durability, California bearing ratio