FREEZE-THAW RESISTANCE OF HIGH SULFATE-SALINE SOIL STABILIZED WITH LIME, GROUND GRANULATED BLAST FURNACE SLAG (GGBFS) AND BASIC OXYGEN FURNACE SLAG (BOFS)

Abstract

Engineers face growing challenges in dealing with problematic soils, particularly those containing sulfates, for infrastructure and construction development. In cold regions, the problem is compounded by freeze-thaw cycling, which can cause durability issues. Calcium-based materials, such as ordinary Portland cement and lime, have been successful in enhancing soil properties. However, their use is often constrained by cost, excessive energy consumption, and their contribution to global carbon dioxide emissions. Furthermore, treatment of sulfate-bearing soils with calcium-based materials can lead to ettringite formation, resulting in volumetric instability and other durability issues. Thus, this study investigated the performance of various mixtures of stabilizers, including lime, ground granulated blast furnace slag (GGBFS), and basic oxygen furnace slag (BOFS), and their behavior under freeze-thaw cycles. A range of engineering, durability, and mineralogical tests were carried out in accordance with standard guidelines. The results showed that both binary and ternary mixtures exhibited similar behaviors regarding optimum moisture content (OMC) and maximum dry density (MDD). As OMC increased, there was a subsequent decrease in MDD, except for ternary mixture I, where MDD slightly increased. Ternary blend II (4% of 70% GGBFS and 30% BOFS) demonstrated the highest UCS before mellowing, and surprisingly, ternary mixture III of the same proportion had the highest UCS after mellowing. All stabilizer blends were effective in reducing the swelling behaviors of untreated soil, with 4% lime being the most effective. However, there was disparity in the DC test, with only 6% and 8% exhibiting better resistance to moisture susceptibility. From a durability standpoint, only 4% of the 70% GGBFS: 30% BOFS mixture before and after mellowing could withstand F-T cycles beyond 40 cycles (20 days) without collapsing, resisting F-T, mass loss, and swelling without collapsing. X-ray microscope analysis summarized that no significant ettringite mineral was detected in all soil samples except for low thaumasite minerals, which were observed in the “control” mellowed soil. Contrarily, the scanning electron micrograph showed the development of needle-like ettringite in almost all the ternary mixtures I and II while demonstrating massive openings and pores in the binary mixture. Therefore, ternary mixtures II and III (4% of 70% GGBFS and 30% BOFS) showed the overall best performance, which exemplifies that stabilizing sulfate-bearing soil with a higher content of slag offers the most promising performance.