Influence of steel slag content on the mechanical and hydraulic properties of compacted silt-bentonite mixtures

Abstract

The reuse of by-products has become increasingly important as a means of minimising the consumption of natural resources and reducing waste disposal. This study examines the potential reuse of steel slag for soil stabilisation, with benefits such as conserving natural resources and mitigating the greenhouse gas emissions associated with the production of conventional stabilising agents. It focuses on evaluating the effect of pozzolanic reactions on the strength and stiffness of both loess silt and silt-bentonite mixtures. The experimental tests included the physical characterisation of granular materials, reactivity tests of the pozzolanicity of soil mixtures, compaction tests, unconfined compression tests, and hydraulic conductivity tests. The impact of the curing period was also analysed to quantify the effects of natural cementation and the development of hydrogels within soil pores on the compacted soil properties. The findings suggest that adding steel slag can significantly increase the strength and the stiffness of compacted loess silts by over 300% and 500%, respectively, after 56 days of curing, substantially reducing the hydraulic conductivity of granular materials, such as the tested silt, as hydrogels partially occupy the pores available for liquid flow. It should be noted that the chemical reactions during hydrogel formation may hinder the free expansion of clay mixtures and release Ca2+ ions, thereby counteracting the expected reduction in hydraulic conductivity when bentonite is added to compacted earthen barriers.