Strength and Mechanism of Carbonated Solidified Clay with Steel Slag Curing Agent

Abstract

Industrial wastes, such as steel slag and desulfurized gypsum, are piled up in large quantities and only a very small portion is recycled, adversely impacting natural ecosystems. Meanwhile, environmental problems caused by CO2 have increasingly received attention. Hence, this study introduces a novel environmentally friendly composite, formed by sodium hydroxide (used as an activator), desulfurized gypsum and steel slag (S-GS). The main objective of this study is to evaluate the potential use of S-GS for solidifying clay under the condition of carbonation curing. Besides, the samples’ characteristics are investigated according to the tests of unconfined compressive strength (UCS), pH, carbonation depth, quality loss and scanning electron microscope (SEM). It is found that the UCS of solidified clay decreases with the increasing water content while it increases first and then decreases with the increasing desulfurized gypsum content, reaching the maximum when the water content is 0.5 times the liquid limit and the content of desulfurized gypsum is 8%. Moreover, compared with the standard curing, carbonation curing can stimulate the activity of S-GS to improve the UCS of samples more effectively. With the increasing carbonation curing time, the mass loss rate and carbonation depth of samples increase while the pH value decreases. Additionally, based on the normalized analysis, the carbonation time has the most significant effect on the UCS. Furthermore, the SEM results indicate that formation of Calcium carbonate and Magnesium carbonate are primary reasons for improving the UCS of the stabilised clay during carbonization. This research promotes steel slag and desulfurized gypsum as green stabilisers for soil stabilization, and the method of carbonation curing contributes to the higher UCS, which also greatly shortens the curing time.