Physico-mechanical and microstructural behaviour of high-water content zinc-contaminated dredged sediment treated with integrated approach PHDVPSS

This paper uses a new integrated method, namely PHDVPSS, which utilizes vacuum pressure (VP) coupled with prefabricated horizontal drain along with solidification/stabilization (SS) for the effective treatment of high-water content dredged contaminated sediment (DCS). This study sought to evaluate the physico-mechanical and microstructural behaviour of high-water content DCS treated with MgO-GGBS (MG) and Portland cement (PC) as PHDVPSS binders and compared to the traditional Portland cement solidification/stabilization (SS-PC) method. Physico-mechanical and microstructural characteristics of the DCS treated with the PHDVPSS method were evaluated by performing a number of tests such as unconfined compressive strength (UCS), toxicity characteristics of the leaching process (TCLP), pH, X-ray diffraction (XRD) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Treatment results showed that the DCS treated with the MG binder in the PHDVPSS method showed superior performance in terms of a significant reduction in the water content and leachability of zinc (Zn) along with higher mechanical strength and dry density of the samples compared to the traditional SS-PC method. After 56-day curing time, VP-MG cases showed 17.6 % and 50 % higher dry density values, resulting in 2.5 and 17.3 times higher UCS values than VP-PC and SS-PC cases, respectively. In contrast, VP-MG cases showed lower pH values than those of VP-PC and SS-PC cases. Moreover, VP-MG cases exhibited 37.5 % and 44.3 % lower leached Zn concentration during a TCLP test than VP-PC cases and SS-PC cases, respectively. XRD and SEM-EDS tests showed that more voluminous hydration products were produced in the VP-MG cases, which in turn produced a dense stabilized matrix and significantly reduced the leachability of zinc.

Automated summary

The study introduced a new integrated method, PHDVPSS, involving vacuum pressure, prefabricated horizontal drains, and solidification/stabilization for treating high-water content dredged contaminated sediment. Results showed that using MG binder in the PHDVPSS method led to superior performance in terms of reduced water content and leachable zinc, higher mechanical strength and dry density compared to traditional solidification/stabilization methods. Additionally, XRD and SEM-EDS tests indicated that VP-MG cases produced more hydration products, resulting in a dense matrix and decreased zinc leachability.