Study on the Strength Development in Cement Stabilized Soft Clay

Abstract

The inherent limitations of the conventional foundations lead to choose an alternative solution, namely, ground improvement technique for solving geotechnical problems. Shallow soil-cement stabilization and in-situ deep mixing technique (cement column) are widely used for soft ground improvement. Mixing of cement converts the existing soft ground into a composite media. The strength development of cement stabilized materials depends on various aspects such as water content, curing time, amount of cementing materials, temperature and type of soils. Hence, the understanding of the strength-deformation characteristics of induced cemented clay is necessary to reflect its behavior in the rational design of the composite ground. In this study, the findings obtained from laboratory investigation on cement-stabilized clay are presented. Typical soft clay from the KUET campus, Khulna, the southwest region of Bangladesh is considered in this investigation. Ordinary Portland cement is used as a cementing agent. The cement was mixed thoroughly with the remolded clay at a percentage of 2.5%, 5%, 7.5%, 10%, 15%, 20%, 25%, 35% and 50% of the solid weight of soil. To have the same initial water content at all cases, soil-cement mixing was done at the liquid limit state of the clay. The soil-cement samples were wrapped properly so that additional water cannot be entered into the samples while kept under water for curing and also to prevent moisture evaporation till the designated rest period. Unconfined compression tests were conducted at a rest period of 0.25, 1, 3, 7, 14, 28 and 56 days to examine the development of strength deformation characteristics with time. The change of water content, unit weight, failure strain, compressive strength and stiffness was also examined at different cement content and rest period. A relationship is established among the cement content, rest period and unconfined compressive strength. Significant changes were also observed in other physical and mechanical properties. Finally, an empirical equation is proposed which can be used with a reasonable degree of accuracy for the estimation of compressive strength at an elapsed rest period for particular cement content.