Effect of pH on the mechanical performances of cement/slag-stabilized marine sediments: Experimental and analytical constitutive modelling

While stabilized marine sediment (SMS) is widely used in construction projects, its mechanical response may be influenced by its environment, such as contact with liquids of different pH value, the extent of which is not well understood. In this context, a marine sediment stabilized with Ordinary Portland Cement (OPC) and Ground-Granulated Blast Furnace Slag (GGBS) is studied in this paper. Unconfined compressive strength (UCS) tests, mass loss analyses and micro-structure evaluations were conducted on SMS specimens having different curing durations (7, 28, 56 and 98 days) and in contact with liquids with different pH values (1, 7 and 10) for 100 days in a tank leaching setup. The results indicate that 1) replacement of OPC by GGBS in the ratio of 1:1 is most efficient in improving the UCS of the SMS considered herein; 2) UCS values determined after leaching at pH=7 and 10 are greater than those without leaching, whereas UCS values after leaching at pH=1 are lower than those without leaching, and 3) a reduced mass loss and a more compact structure occurs with greater leachate pH. Based on the experimental observations, a novel elastoplastic constitutive model with analytical stress–strain solutions is presented to describe the mechanical behaviour of SMS. The influences of two factors (leachate pH and curing durations) on the model parameters are analysed using the binary quadratic nonlinear regression method. The analytical model is shown to be capable of predicting the mechanical performance in various pH environments, representative of a variety of SMS applications.