Abstract
Expansive soil shows dual swell–shrink which is not suitable for construction. Several mitigating techniques exist to counteract the problem promulgated by expansive clayey soils. This paper explored the potential mecho-chemical reinforcement of expansive clayey soil to mitigate the effect of upward swelling pressure and heave. The polypropylene fiber is randomly distributed in the soil for mechanical stabilization, and the industrial residual silica fume is used as a chemical stabilizer. The experimental analysis was made in three phases which involved tests on mechanically-reinforced expansive soil, using randomly distributed polypropylene fibers with different percentages (0.25%, 0.50%, and 1.00%), and which were 12 mm length. The second phase of experiments was carried out on chemical stabilized expansive soil with different percentages (2%, 4%, and 8%) of silica, and the next phase of the experiment focused on the combination of mecho-chemical stabilization of the expansive soil with different combinations of silica (i.e., 2%, 4%, and 8%) and polypropylene fibers (i.e., 0.25%, 0.50%, and 1.00%). Maximum dry density (MDD), optimum moisture content (OMC), liquid limit (LL), plastic limit (PL), plastic index (PI), grain size, and constant volume swelling pressure tests were performed on unreinforced and reinforced expansive soil, to investigate the effects of polypropylene fiber and silica fume on the engineering properties of expansive clayey soil. The experimental results illustrate that the inclusion of polypropylene fiber has a significant effect on the upward swelling pressure and expansion property of expansive soil. The reduction in the upward swelling pressure and expansion is a function of fiber content. These results also indicated that the use of silica fume caused a reduction in upward swelling potential, and its effect was considerably more than the influence of fiber.
Highlights
Expansive clayey soil, which is copious in tenacious hydrophilic minerals such as illite and montmorillonite, is a typically problematic expansive soil conceived in natural geological processes
A constant volume swelling pressure test was conducted by varying the percentage of polypropylene fiber content (i.e., 0%, 0.25%, 0.50%, and 1.00%) and silica fume (0%, 2%, 4%, and 8%), to propose the optimum amount of the fiber reinforcement and silica fume needed to mitigate the upward swelling pressure exerted by the expansive soil
This depicts that the swelling pressure decreases with an increase in polypropylene fiber content and with the increment of the silica fume content
Summary
Expansive clayey soil, which is copious in tenacious hydrophilic minerals such as illite and montmorillonite, is a typically problematic expansive soil conceived in natural geological processes. Due to their inherent swelling–shrinkage nature, are considered as inadmissible construction materials for building and for transportation engineering applications [5]. Chemical stabilization methods make expansive clay soils stable under compression, but contribute minimally to the tension. The primary focus of this paper is to evaluate the performance of the polypropylene fiber as an effective mechanical reinforcement and of silica fume as an environment-friendly chemical stabilizer, as alternatives for the expansive soil [29,30]. A constant volume swelling pressure test was conducted by varying the percentage of polypropylene fiber content (i.e., 0%, 0.25%, 0.50%, and 1.00%) and silica fume (0%, 2%, 4%, and 8%), to propose the optimum amount of the fiber reinforcement and silica fume needed to mitigate the upward swelling pressure exerted by the expansive soil
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