Improving soil stabilisation with Duraflex admixture: effects on strength and porosity

The possibility of improving the engineering properties of a silty clay from Calgary, Alberta, Canada, was assessed. Specimens made of silty clay soil (S), silty clay-plus-cement (SC), and silty clay-plus-cement-plus-Duraflex admixture (SCD) were tested for either unconfined compressive strength (UCS) or splitting tensile strength (STS). Two curing conditions were used (100% RH and the laboratory) for different curing durations (7, 14, 28 days, and 10 months). Lab-cured 10-month specimens with Duraflex admixture (DFI) were 10–25% statistically stronger than SC specimens and more than twice the strength of soil alone. Small but significant variations in STS/UCS ratios ranging from 0.10 to 0.27 were observed for different curing durations and conditions. However, when the same type of specimens were cured under identical conditions and duration, no statistically significant variation occurred. Brunauer–Emmett–Teller (BET-N₂) analysis resulted in a notable reduction in micro- and mesopores, pore surface area, and pore volume through the addition of DFI, suggesting the addition of that admixture filled more pores with cementitious material. In addition, matric suction analysis through the filter paper method confirmed that SCD resulted in higher suction strength than SC and S, implying lower porosity and thereby statistically higher UCS and STS values.