Carbonation properties of dredged slurry pre-dried with steel slag powder: Effects of clay minerals and organic acids

Abstract

The carbonation properties of dredged slurry pre-dried with steel slag powder were investigated in this study, and steel slag powder was also involved in the drying process. However, it remains unclear how the interaction between steel slag and clay minerals or organic acids in the slurry affects the carbonation performance of the dried soil (DS), and the underlying mechanism needs elucidation. In this study, quartz, montmorillonite, and fulvic acid (FA) were used to prepare five types of artificial soil testing samples. The artificial soils were then made into slurry and dried using steel slag powder to obtain DS. The carbonated soil (CS) was attained by carbonation stabilization/solidification (S/S) of DS, and the effect of montmorillonite and/or FA on the optimal moisture content for carbonation (C-OMC) and the strength ratio of carbonation (Rcs) of the CS were evaluated by unconfined compressive strength. In addition, the mixed soil (MS), as the reference group of DS, was prepared by combining artificial dry soil directly with steel slag to help understand how the interaction between montmorillonite or FA and steel slag during the drying process. X-ray diffraction (XRD), thermogravimetry and derivative thermogravimetry (TG/DTG), and pH tests were used to characterize the changes of microscopic mineral and pH value during the drying process from MS to DS, and the carbonation process from DS to CS. The results showed that the existence and content of montmorillonite can reduce the carbonation efficiency of DS, and a small amount of FA is conducive to improving the carbonation efficiency of DS. By comparing the composition changes of DS and MS, it was confirmed that the interaction between steel slag and montmorillonite or FA existed in the drying process, and this interaction affected the carbonation performance of DS by changing the pH value of DS.