Strength and stiffness of cement-treated marine dredged clay at various curing stages

This paper evaluates the unconfined compressive strength (qu) and stiffness (G0) of marine dredged clay treated by ordinary Portland cement. Although the cement-treated marine dredged clays have been used as filling materials for construction or reclamation, many of previous studies were more applicable to soft foundation improvement methods such as deep cement mixing and jet grouting. This study aims to investigate how the qu and G0 of cement-treated marine dredged clay vary with water and cement contents at various curing times and to observe the relationship of the qu and G0. A series of unconfined compression and bender element tests were carried out for cement-treated Tokuyama dredged clay with different values of water and cement contents at various curing times, ranging from 5 h to 90 days and the relationship between the qu and G0 was examined. Specific volume normalized by that at liquid limit were applied to facilitate parametric study. The study revealed that the behavior of qu with curing time are closely similar to that of G0, and a trend of development of qu and G0 change before and after 3 days of curing time. The qu and G0 can be correlated with the normalized specific volume. The qu and G0 exhibits a linear relationship for the curing time. Based on these results, the empirical equations for estimating qu are proposed using G0 estimation equations and the relation between qu and G0. In addition, the applicability of formulas based on the relation of qu and G0 was evaluated using the relation of G0 and secant modulus (E50). It was confirmed that the G0 can successfully describe the improvement effect of cement-treated marine dredged clay and can be used to effectively predict the qu using the proposed formulas.