Preparation of Artificial Aggregates from Marine Dredged Material: CO2 Uptake and Performance Regulation

Abstract

A continuous treatment process using steel slag powder including foam drying and carbonation processes (termed the SSFD-C method) is a novel technology previously developed in our laboratory. It has achieved the first application of carbonation solidification technology to recycle marine dredged material with high moisture content. The aim of this study is to investigate CO2 uptake and performance regulation in the preparation of carbonated eco-aggregates (CEAs) from dredged soils processed using the SSFD-C method. Steel slag and lime hydrate independently contribute to the strength of CEAs. However, the influence they exert on CO2 uptake, along with other properties, such as pH values and water absorption of CEAs, remains unclear. Furthermore, it is important to clarify whether the soluble silica in a CEA originates from dredged soil or steel slag, as a CEA has the potential to provide silica nutrients to plants. The findings indicated that within the initial three hours of carbonation, the strength of CEAs could approximate 65% of the ultimate stable strength. The moisture absorption for CEAs was noted to be in the 26–30% range. Carbonation over a 24 h period can lower the pH of the CEA to less than 10, and the carbonation reaction can penetrate the core of the 10–15 mm CEA pellets. Carbonation of the lime hydrate fraction was more favorable to increase the CO2 uptake of the CEA, and carbonation of the steel slag fraction was more favorable to decrease the pH value and water absorption of the CEA. The water-soluble silicon of the CEA was found to have been mainly derived from steel slag, while it was established that carbonation could increase the water-soluble silicon content of the CEA by 5–8 times. The result of this study could provide theoretical guidance for regulating the performance of CEAs.