ABSTRACT
Pulverized Coal Bottom Ash (PCBA) and Superphosphate Fertilizer Processing Residue (SFPR) are capable of improving the stability of laterite soils. Varing admixture ratios of PCBA and SFPR severally with defective laterite soil from Shika area of Kaduna State produced substantial increase in the index and strength properties of the soil. The liquid limit, plasticity index and CBR of the soil were increased. Strength increase of up to 160 percent was obtained at mere 2 percent stochiometry for SFPR stabilized soil and 200 percent at 6 percent stochiometry for PCBA stabilized soil. Curing improved the strengths of both SFPR and PCBA stabilized soils further by over 150 percent. Both SFPR and PCBA stabilized soils developed high early strength on curing, attaining peak strength within 14 days for low dose, low energy compacted admixtures. For high 'dose' admixtures, both SFPR and PCBA exhibited pozzolanic properties gaining strength gradually with ageing. Pozzolanic strength gains ranged from 20 to 60 percent. Unconfined compressive strength (UCS) for both SFPR and PCBA exceed 1.5 MPa and unsoaked and soaked CBR were 100 and 80 percent respectively, making both SFPR and PCBA suitable materials for subbase and base stabilization. The results of the research can be applied to reduce incidence of distressed roads all over the country arising from lack or insufficient fund and high cost of inputs. The results. will particularly suit perenially neglected rural roads and small private roads that are outside regular orbit of public financing. The results of the research if utilized would also reduce environmental pollution constituted by phosphate residue and spent coal heaps. It will also add value to mining portfolios that depend on phosphate and carbon minerals.