Sustainable Utilization of Reclaimed Gypsum and Silica Fume as a Binary Additive to Improve the Subgrade Materials

Abstract

It is a CH soil that exhibits tremendous volumetric changes as the moisture content changes. This intrinsic characteristic of CH soil has detrimental effects for both human beings and civil infrastructure. The CH soil has been improved by chemical stabilization, i.e., SF and RG of ratio 2:1 in the form of CBA, when it is added to the CH soil. The results show significant improvement in three major areas, such as geo-technical engineering, sustainable environments, and commercial benefits. The physical and mechanical properties of the CH soil, including Atterberg’s limits, sieve analysis, compaction curves, and specific gravity, witnessed improvement after treatment with CBA. Also, the geo-technical parameters of CBA samples are tested in two ways: one by macro tests, which are UCS, CBR, and odometer laboratory tests, and another by micro tests, which are SEM, EDX, and X-ray analyses, both of which reflect the strength, stability, and durability of the soil. The ultimate compressive strength, yield stress, CBR value, and optimum moisture content increased, whereas maximum dry unit weight, strain at failure, deformability index, compression index, void ratios, liquid limit, and plasticity index decreased. Next, environmental hazards like H2S, which is found in RG, when emitted directly into the air or landfilled, cause acid rains. Finally, it boosts the economy as well, because it is difficult to landfill RG and SF. In short, the additives used in the stabilization improved the overall strength of civil infrastructure and tend to save billions of dollars in terms of reducing environmental hazards, which in turn will improve the economy in one way or another.