Preliminary investigation of high-water content dredged sediment treated with chemical-physical combined method at low cement content.

Abstract

Land reclamation projects are increasingly incorporating dredged sediment from waterways. The high water content of dredged sediment is a major issue, making the dewatering process difficult and time-consuming. The chemical-physical combined method (CP) is therefore used in this study, which simultaneously uses vacuum dewatering by utilising vacuum pressure (VP) in conjunction with prefabricated horizontal drain (PHD) and Portland cement (PC)-based solidification/stabilisation (SS), thereby significantly reducing the duration of treatment of DS with high water content. The effectiveness and feasibility of the chemical-physical combined method with Portland cement (PC) as abinder are evaluated and compared with the traditional PC-based solidification/stabilisation (SS) method. A number of experimental tests were performed to accomplish the objectives of the study, such as unconfined compressive strength (USS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The experimental results indicated that the CP method showed better performance compared to the traditional SS method in treating high water content DS at low cement content. The water content of DS treated with the chemical-physical combined method was reduced by half in just about 3days, and the final rate of settlement was 2.9 times higher than with SS-treated DS. The USC results showed that the strength of CP cases was 4.8 times higher than SS-treated DS after 56days of curing age. The microstructural tests revealed the development of CSH and CASH as major hydration products of both CP and SS cases. Moreover, CP cases exhibited a densely stabilised matrix compared to SS cases.