Effect of Palmyra Palm Leaf Ash on Cement Stabilization of Makurdi Shale

Makurdi Shale was treated with palmyra palm leaf ash (PPLA) and cement to assess its suitability as a material in construction of flexible pavement. Classification, Compaction, Consistency, California bearing ratio (CBR) and Unconfined compressive strength (UCS) tests, were conducted on the shale specimen treated with, cement and PPLA in a combined incremental order of 2% up to 10% of cement and 2% up to 14% of PPLA of dry weight of soil sample respectively. Results of tests showed that Makurdi shale is an A-7-6, high plasticity (CH) and high swell potential soil by the American Association of State Highway and Transportation Officials (AASHTO), Unified Soil Classification System (USCS) and Nigerian Building and Road Research Institute (NBRRI) classification systems respectively. The plasticity index (PI) reduced from 30.5% for untreated Makurdi shale to 4% at 10% cement +14% PPLA contents. The maximum soaked CBR and 7 day UCS values of 92% and 1041 kN/m2 were obtained at 10% cement+14 % PPLA contents respectively. From the results, Makurdi shale treated with a combination of 10%cement+14% PPFA with a soaked CBR value of 92 %, 7 day UCS value of 1041 kN/m2 and 82 % value of resistance to loss in strength, satisfied the requirement for sub-base specification. It is therefore recommended for use as sub-base materials in flexible pavement.