Effects of cement and lime stabilization on geotechnical characteristics of a regional clay

Abstract

In the present investigations cement and lime stabilization of a regional medium expansive clay has been carried out to find the effects of cement and lime stabilization on the selected soil. Here the said clay sample was collected from Mouchak in Gazipur district. The collected sample of the selected site was inorganic clay of low plasticity and medium expansive. As additives, ordinary Portland cement and slaked lime were used in amount of 2%, 5% and 8% of dry weight of collected soil sample individually for index tests, shrinkage limit tests, linear shrinkage tests, standard proctor tests and unconfined compressive strength tests. The said additives were 5% of dry weight of collected soil individually for direct shear tests. Unconfined compressive strength tests were performed on soil-additive mixtures compacted at optimum moisture content (OMC) and then consolidated undrained direct shear tests were performed on soil-additive mixtures compacted at wet side of OMC at 95% of maximum dry density. Cement stabilized samples for both unconfined compressive strength tests and consolidated undrained direct shear tests were cured for 7, 14, 28 and 56 days individually. On the other hand, lime stabilized samples for unconfined compressive strength tests were cured for 7, 14, 28 and 56 days individually but for consolidated direct shear tests the samples were cured for 7, 28 and 56 days individually. Comparison among unconfined compressive strengths which were obtained from different researches on cement and lime stabilization have also been studied.

Compared with the untreated samples; plasticity indices and percentages of linear shrinkages of the selected soil-additive mixtures do not change significantly while shrinkage limits of the selected soil-additive mixtures increased significantly. Change in OMC and maximum dry density due to selected cement and lime stabilization is also not significant.

Most of the data found from unconfined compressive strength tests show that cement is better choice than lime to increase unconfined compressive strength of the selected soil, although more study is required to determine the effects of longer curing period and more admixture content. The range of unconfined compressive strength of the selected soil-cement mixtures is 530 kN/m2 to 2195 kN/m2. For lime treated soil, the said range is 605 kN/m2 to 1990 kN/m2. It is found that compressive strengths of samples treated with 8% cement and cured for 7 and 28 days satisfied the PCA (1956) for the compressive strength of soil cement mix. It is also found that for all cement contents and all curing ages of the present investigation except 2% cement content with 56 days curing, compressive strength of the stabilized samples fulfilled the requirements of soil-cement mix for use in road sub-base and base subjected to light traffic, as proposed by Ingles and Metcalf (1972).

For selected cement treated samples, axial failure strains and initial tangent moduli do not show a specific trend. The ranges of axial failure strains and initial tangent moduli for selected cement treated samples are 0.57% to 1.2% and 60200 kN/m2 to 526700 kN/m2 respectively. For selected lime treated samples too, initial tangent moduli do not show a specific trend. Most of the data of unconfined compressive strength tests show that axial failure strains of selected lime treated samples decrease with increments of lime contents in the samples. The ranges of axial failure strains and initial tangent moduli for selected lime treated samples are 0.76% to 4.6% and 45300 kN/m2 to 95800 kN/m2 respectively.

It is observed that consolidated undrained cohesions of lime treated samples decrease with increases of lime in the samples while the said cohesions of cement treated samples increase with increases of cement in the samples. On the other hand, consolidated undrained angles of internal frictions increase with increases of lime in the samples while the said angles of internal frictions of cement treated samples decrease with increases of cement in the samples.

For both cement and lime treated selected clay samples, shear stress vs. shear displacement curves show that the clay samples are over consolidated clay samples but all shear displacement vs. corresponding changes in height curves do not show the said nature.