RESUMEN

Steel slag (SS) is a byproduct that comes from the production of crude steel in alkaline oxidation furnaces. Resource utilization of steel slag, a calcium-silicon solid waste, is an urgent problem. This paper investigates a solid waste disposal method that applies different steel slag contents to modify dispersive soil. The engineering properties and modification mechanisms of dispersive soil specimens are studied and revealed by performing microstructure, mineral evolution, unconfined compressive strength (UCS), and tensile strength analysis. The pinhole test, mud ball crumb test (BCT), and mud cube crumb test (CCT) were carried out to determine the dispersivity of the soil specimens. Results show that when the steel slag content increases from 1% to 10%, the unconfined compressive strength and tensile strength increase by 176.05% and 75.40%, respectively. For soil specimens without curing time under 50 mm water head, the weight loss of the specimen with 10% steel slag content decreases by 72.03% compared to specimens with 1% steel slag content. Microstructural and mineralogical analyses indicate that the hydration reaction of steel slag changes the ionic composition of the soil and generates reaction products with effects such as filling and connection. To sum up, steel slag effectively improves water stability and mechanical properties of dispersive soil.

Asunto(s)

RESUMEN

Dispersivity of clay soils is one of the most important issues that should be considered in civil engineering projects. Dispersive soils are clay soils that are easily washed in water with low concentrations of salt; these clay soils usually contain high levels of sodium ions in their adsorption cation sites. Kaolin, sepiolite (fibrous clay), and bentonite soils are among the most important and useful industrial materials. Therefore, in this study, these three clay soils were selected to investigate dispersivity potential by adding 4% of dispersive materials (Sodium hexametaphosphate) and performing shear strength, crumb, double hydrometer, pinhole tests, and chemical experiments. Results indicated a change in the Sodium Adsorption Ratio (SAR) in the following order: kaolin > sepiolite > bentonite. Stabilization practices using chemical methods were done after performing soil divergence with sodium hexametaphosphate. CaCl2, CaSO4, AlCl3, and Al2 (SO4)3 were used for chemical stabilization to assess the effect of ion valence on soil improvement parameters. Results obtained for chemical properties showed that, stabilization potential was in the following order: kaolin > sepiolite > bentonite; meaning that clay soils with lower cation exchange capacity have more remediation potential and are more susceptible to dispersion. The role of calcium and aluminum cations was prominent in improving mechanical and dispersivity properties, respectively. In general, further dispersion potential of clays in the same Na+ concentration was found to be related to a decrease in the cation exchange capacity, specific surface area, and plastic index. Soil dispersion was directly associated with diffuse double layer and electrostatic forces while; soil strength parameters were mainly dependent on cementation and connection of soil particles to each other. Consequently, it was observed that, clay soils with suitable engineering properties (higher strength and compaction or lower Atterberg limits) are more sensitive to dispersion compared to other types of clay with higher CEC and plasticity values.

RESUMEN

Dispersive soil arises significant problems that need attention in geotechnical Engineering. Such soils are easily erodible and keep apart due to the difference in moisture content and exchangeable sodium. This study focuses on enhancing sub-grade of the road by stabilizing dispersive soil with lime, and it provides better index properties, reduces dispersivity, increases Unconfined compression strength, and California Bearing Ratio value with an increasing lime quantity and curing in different test conditions. The effective lime content should be 7% to 9 % of dry soil weight as it provides high strength and quality of subgrade pavement rating.