Laboratory Performance Evaluation of Stabilized Sulfate Containing Soil with Lime and Class C Fly Ash

A laboratory study was undertaken to evaluate the effectiveness of lime and Class C fly ash (CFA) as soil stabilizing agents for a sulfate containing, A-7-6 type CL Oklahoma soil. Using various percentages and employing as criteria the 28 day unconfined compressive strength test (UCS) and the pH value, the optimum amount of lime (5 %) and CFA (16 %) were determined. Using these percentages further performance evaluation was effected. Cylindrical samples were compacted at optimum moisture content (OMC) and cured for 28 days for resilient modulus (M_R) and UCS tests. Laboratory tests revealed that the M_R and UCS of soil increased substantially with the addition of both lime and CFA compared to those of raw soil at OMC. The M_R value increased from 50 Mpa of the raw soil to 250 Mpa of its stabilized counterpart, and the UCS improved from approximately 100 kPa to 1000 kPa. In addition, 3-D swelling and Tube suction tests (TST) were conducted on cured samples to determine swelling and moisture susceptibility behaviors; however, the volume change was minimal, from 1651 cm³ to 1664 cm³, and the dielectric constant decreased from 30 to 20. The scanning electron microscopic (SEM) studies showed a change in the soil fabric with the formation of some crystals and qualitative changes in the densification resulting from the mastic filling part of the original voids. Finally, the change in the plasticity index was observed to be from 22 % to 10 %, a manifestation of the ameliorating effects of stabilization.