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Soil electrical resistivity has been used quite extensively for assessing mechanical properties of chemically treated soils, in the recent past. One of the most innovative applications of this technique could be in the field of ground improvement wherein carbonated reactive magnesia (MgO) is employed for treating soils. With this in view, a systematic study which targets the application of electrical resistivity to correlate physical and strength characteristics of the carbonated reactive MgO-admixed silty soil is initiated and its details are presented in this manuscript. To achieve this, reactive MgO-admixed soils were carbonized by exposing them to CO 2 for different durations, and subsequently their electrical resistivity and unconfined compression strength were measured. In this context, role of a parameter, ratio of the initial water content of the virgin soil to reactive MgO content (designated as w 0 /c), has been highlighted. It has also been demonstrated that w 0 /c is able to correlate, uniquely and precisely, with the physico-chemical parameters of the soils (viz., unit weight, water content at failure, porosity, degree of saturation and soil pH), electrical resistivity and unconfined compressive strength at various carbonation times. In addition, microstructural properties have been obtained from the X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry analyses. These properties have been used to substantiate the findings related to the carbonation of the reactive MgO-admixed soils.

The potential of lignin based by-product to stabilize silt was evaluated. The physical and mechanical properties of silt in its natural state as well as when treated with varying proportions of lignin were analyzed. The parameters tested include the particle size distribution, Atterberg limits, compaction characteristics, unconfined compressed strength, pH value and the electrical resistivity. To understand the stabilization mechanism of lignin-treated silt at microscopic level, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and Fourier transform infrared resonance (FTIR) spectroscopy were also carried out on lignin and representative samples after 28-day curing. The results indicate that the engineering properties of silt are improved by the addition of lignin. Particle size distribution is changed and plastic index is reduced from 8.8 to 7.7. After improvement, the maximum dry density increases and the optimum moisture content decreases, while the change of dry density with moisture content is enhanced. The treated silt has greater strength performance than the natural silt in terms of unconfined compressed strength and all the samples have a pH value lower than 10. Curing time and moisture content have a significant impact on unconfined compressed Downloaded by [Gebze Yuksek Teknoloji Enstitïsu ] at 19:23 20 December 20142 strength but almost no effect on pH. The micro-chemical analysis reveals that the improvement of performance exhibited by lignin-treated silt may be mainly attributed to the cation exchange and the formation of more stable soil structure by lignin cementing.The stabilization mechanism of lignin treated silt was proposed according to the results of chemical analysis. It is shown that the lignin based stabilizers have a great potention to improve the engineering properties of silt.

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