Parameters controlling the expansive behavior of bentonite-kaolin mixtures stabilized with alkali-activated waste

Abstract

Expansive soils can cause large-scale damage to the infrastructure. Soil stabilization with Portland cement and lime has been widely utilized as a solution to this problem. However, these stabilizers are non-renewable and energy-intensive. Alkali-activated binders are alternatives with lower carbon dioxide emissions. This research evaluated an expansive soil stabilization with an alkali-activated binder produced from sugarcane bagasse ash (SCBA), hydrated eggshell lime (HEL) and sodium hydroxide (NaOH). Free-swelling tests alongside a statistical analysis evaluated the influence of dry unit weight (12.5 and 14.5 kN/m³), binder (4 and 10%) and moisture content (19.7 and 24.7%) and curing time (0 and 7 days) on the stabilized mixtures. A four factors factorial design with duplicates and central points was outlined. To better understand the NaOH and SCBA influence over the soil expansion additional tests were performed. In general, an increase on the studied factors reduced swelling, especially binder content. However, the alkali-activated cement presented no clear correlation between higher density and higher expansion. Swell reduced from 13.8% (12.5 kN/m³ and 19.7% moisture) and 8.8% (12.5 kN/m³ and 24.7% moisture) to 2.5% and 0%, respectively, after 7 days and 10% binder addition for the alkaline cement. For Portland cement, swell reduced from 13.8% (10.2 kN/m³ and 22.5% moisture) and 12.5% (10.2 kN/m³ and 27.5% moisture) to 1.8% and 1%, respectively, after 7 days and 4% binder addition. Samples containing NaOH expanded less than samples molded with only water. Finally, the alternative binder might be a viable option to replace Portland cement for expansion control.

Keywords:
Sugarcane bagasse ash; Hydrated eggshell lime; Alkaline cement; Expansive soils; Swelling