Strength and microstructural characteristics of cement-solidified salt-rich dredged silt modified by nanoparticles

Abstract

Chemical solidification based on cement is one of the most widely used methods to treat marine dredged silt (DS) with very poor engineering properties. This study investigated the strength and microstructure of cement-solidified salt-rich dredged silt (CSDS) modified by nanoparticles. The unconfined compressive strength (UCS) test showed that the UCS of CSDS containing 9% NaCl was obviously lower than that without NaCl. Furthermore, the detrimental effect of chloride salt on the UCS increased with its content significantly. The nano-SiO2 (NS) used as cement additives can significantly improve the UCS of CSDS and adding 8% NS can reduce cement usage by at least 40%. Compared with NS, the nano-MgO (NM) mainly improved the early UCS of CSDS within 7 days. The needle-like Friedel’s salt (the reaction product of chloridion with cement) and lamellar brucite (expansive mineral) were clearly detected by the X-ray diffraction test. The calcium silicate hydrate and magnesium silicate hydrate mainly contributed to construct the skeleton, which was confirmed by the scanning electron microscopy images. The NS and NM with high reactivity can be used as effective cement additives to overcome the negative effect of chloride salt, so as to increase the strength of CSDS.