Abstract
Water-repellent soils have a potential as alternative construction materials that will improve conventional geotechnical structures. In this study, the potential of chemically treated water-repellent kaolin clay as a landfill cover material is explored by examining its characteristics including hydraulic and mechanical properties. In order to provide water repellency to the kaolin clay, the surface of clay particle is modified with organosilanes in concentrations (CO) ranging from 0.5% to 10% by weight. As the CO increases, the specific gravity of treated clay tends to decrease, whereas the total organic carbon content of the treated clay tends to increase. The soil-water contact angle increases with an increase in CO until CO = 2.5%, and then maintains an almost constant value (≈134.0°). Resistance to water infiltration is improved by organosilane treatment under low hydrostatic pressure. However, water infiltration resistance under high hydrostatic pressure is reduced or exacerbated to the level of untreated clay. The maximum compacted dry weight density decreases with increasing CO. As the CO increases, the small strain shear modulus increases, whereas the effect of organosilane treatment on the constrained modulus is minimal. The results indicate that water-repellent kaolin clay possesses excellent engineering characteristics for a landfill cover material.
Highlights
Landfill needs a final cover system to prevent the uncontrolled release of landfill gas and the infiltration of precipitated water into the waste [1,2]
To examine the grafted pattern of organosilanes after treatment, field emission scanning electron microscopic (FESEM) and energy dispersive X-ray (EDX) analyses were carried out using a Hitachi S-4300 instrument
The irregular spatial distribution patterns of grafted silanes would be related to heterogeneous surface minerals (Figure 3b) due to presence of low and high surface energy sites of the mineral, because the silylation relies on the reactivity of the clay mineral surface [39]
Summary
Landfill needs a final cover system to prevent the uncontrolled release of landfill gas and the infiltration of precipitated water into the waste [1,2]. The ET cover system relies on the water storage capacity of the soil layer, rather than the hydraulic conductivity of the soil layer, to minimize the infiltration. Two general types of ET cover systems have been used: a monolithic barrier and a capillary barrier. A monolithic barrier uses a single layer of fine-grained soil such as silt or clayey silt, whereas a capillary barrier consists of a fine soil layer over a coarser layer. A capillary barrier can retain more water than a monolithic cover with equal thickness [6,7,8], the retained water can infiltrate relatively quickly into the body of the landfill when a fine-grained soil layer within a capillary barrier becomes fully saturated [9,10]
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