Long-term mechanical-sustainable performance of PBFC binder systems in stabilization of Hong Kong marine deposits

An experimental study is conducted to reveal the effects of mix ratio of ground granulated blast slag (GGBS) to ordinary Portland cement (OPC) and the total dosage of Portland blast-furnace cement (PBFC) binders on long-term strength of stabilized Hong Kong marine deposits (HKMDs) and sustainability of binders. The active zone of strength gain is determined for the HKMDs, which thus provides guidelines for the binder dosage used in the engineering design. The GGBS/OPC mix ratio governs the balance between reaction rate and source items of pozzolanic reaction, which results in a parabolic pattern of UCS with respect to the mix ratio and yields the greatest UCS at the mix ratio of 7:3. The strength development of HKMDs stabilized with high GGBS/OPC ratios tends to be more time-sensitive, because the lack of alkaline environment caused by insufficient OPC hydration can be compensated by prolonged curing time. Based on the results from derivative thermogravimetry (DTG), it is found that the treatment of 28-day curing does not provide enough time to consume the products from the primary hydration reaction, and the pozzolanic reaction remains active at the curing time of 180 days. The micro-scale binding structures observed from scanning electron microscope (SEM) imaging indicate that the interconnect structure builds a network of supportive forces that increase the bond strength by forming an ‘interlock’ effect within the soil matrix. Based on the long-term mechanical-sustainable analysis, a design chart is developed for screening the mix schemes to meet both sustainable and mechanical criteria, and selecting the optimized mix scheme that achieves upgraded mechanical properties with a lower carbon emission by involving long-term mechanical metrics.