Utilization of Blast-Furnace Slag as a Standalone Stabilizer for High Sulfate-Bearing Soils

Abstract

This paper presents experimental results and analysis of sulfate-bearing soils treated with ground granulated blast-furnace slag (GGBS). The experiments involve the unconfined compression strength test, shrinkage, free swelling, suction measurements, and microstructural examination. Short- and long-term swelling tests were conducted to inspect the durability of GGBS stabilization against the sulfate-induced heave. The concept of the shrinkage curve was employed to elucidate how GGBS stabilization alleviates soil shrinkage behavior and alters the pore size distribution. The results manifested that 7% GGBS was sufficiently adequate to improve the 28-day strength of the tested sulfate-bearing soils about five times. The GGBS treatment mainly results in the decline of calcium sulfate content and the formation of calcium silicate hydrate, ettringite, and calcite. The results of long-term swelling tests indicated a delayed sulfate-induced heave that started beyond a month from the time of exposing the treated soils to water. The delayed heave was still not significant as compared with that of the untreated control soil specimens. Accordingly, it is recommended that the treated sulfate-bearing soils are tested with the selected GGBS content for any delayed swelling before application in the field. The GGBS treatment has significantly escalated suction magnitude during curing mainly due to the consumption of water in the hydration process and the formation of ettringite.