Time dependent mechanical behavior of high plastic soils treated with marble and glass powder composite

Abstract

Problematic soils are those which have the potential to shrink/swell, collapse, disperse and undergo excessive settlement or even fail under relatively low stress conditions. Several chemicals and admixtures have been used in previous studies for stabilization of expansive soils. This study is focused on expansive/high plastic soils which has the properties of swelling/ shrinkage, high plasticity and even low bearing capacity in the presence of moisture content which makes them inadequate for their use in construction. Samples of expansive soil were collected from Nandipur village district Gujranwala Punjab, Pakistan. Two industrial wastes marble powder (MP) and glass powder (GP) produced in factories during crushing of marble and glass pieces have been used in binder form to study its effect on index and strength properties. Also, viscous properties of geomaterials such as effects of different loading rates on the stress–strain behavior, including creep deformation play an important role in the prediction of short and long-term residual ground deformation and structural displacement. First marble powder was added to the soil with various percentages from 0% to 10% by dry unit weight of the soil with each increment of 2.5%. Several laboratory tests such as consistency limits, proctor, unconfined compressive strength, direct shear and swell potential have been performed. Based on unconfined compressive strength test results 7.5% marble powder was found as the optimum content. Then, by fixing the optimum content of marble powder, glass powder was added at different percentages from 0% to 15% with addition of 2.5% for each increment. Based on results the optimum content found in composite form was 7.5% for marble and 10% for glass powder. For microstructural analyses XRD, SEM and XRF tests were performed to study the mineralogical and morphological characteristics of virgin soil and modifications happened during the stabilization process. It was x observed that plasticity index, optimum moisture content(OMC) and percent swelling was decreased after addition of MP&GP composite to the expansive soil. Consistency limits were reduced by 34%, swell potential by 42% and OMC by 40% while maximum dry density was increased by 8%. Cohesion and UCS and CBR has been increased by 85%, 80% and 75%, respectively, compared to the virgin soil. SEM, XRF and XRD validate the findings of UCS and direct shear tests where in the structure of stabilized soil several silicates and aluminates gels has been observed. The strength and stiffness of the stabilized soil increase with the increase of ageing period due to the development of cementitious hydrates which are produced because of the reaction between calcium silicate from MP with soil and aluminum silicate from GP and soil. Several UCS tests were also performed for the soil stabilized with optimized content at three different loading rates of marble powder, marble and glass powder composite and an increase in the strength and stiffness of the stabilized samples were observed with the increase in loading rate.