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.

Keywords:

• Dredged silt
• solidification/stabilization
• chloride salt
• nano-SiO₂
• nano-MgO
• strength development

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The authors acknowledge the financial support from the start-up fund for doctoral research of Suzhou University [grant no. 2019jb18], University Students’ Innovation and Entrepreneurship Program of Anhui Province [grant nos. S202010379108 and S202010379100X] and 2014 National open project of Suzhou Regional Development Collaborative Innovation Center (general) [grant no. 2014SZXTKF07]. Dual-ability teaching team project of Suzhou University [grant no. 2020XJSN06], Demonstration Teaching Organization of Anhui Education Department (No. 416).