Geotechnical evaluation of untreated and cement-treated Ajali Sandstone from southeastern Nigeria

The grain size analysis and the Atterberg limit values indicate that the Ajali Sandstone falls into the A-3 and SP-SW classes of the AASHTO and the Unified Soil Classification systems respectively. The low values of the coefficient of uniformity 2.9-3.4 show the deposit is uniformly graded and the soil is deficient in silt-clay fractions. At the optimum moisture content of 8% the untreated soil has a maximum dry density of 1.77 Mg/m3. The CBR of the soil when compacted to the standard Proctor optimum and soaked for three days is 10%. To establish the effective cement requirement of the soil, 5, 7, 9 and 110y weight of Portland cement was added to the soil. Results show that 80f the stabilizer meets the required minimum CBR of 100% and the 7-day uniaxial compressive strength of 1.4MPa (l.4 N/mm2). On ageing, the stabilized A-3 soil gains appreciably in strength.