Experiment and Mechanism Analysis on the Solidification of Saline Dredger Fill with Composite Slag Solidifying Agent: A Case Study in Caofeidian, China

Most areas of Caofeidian (Tangshan Caofeidian New District in Hebei Province, China) were formed by land reclamation, where the dredger fill has a high water content and a high salt content. The solidification of Caofeidian’s dredger fill is difficult because of salinisation, as well as environmental and economic factors. This article proposes a composite slag solidifying agent. The optimal proportion of various additives was determined by an unconfined compression test and orthogonal design. Next, a microanalysis was carried out by SEM and XRD tests to characterise the solidification mechanism of the composite slag solidifying agent. The results reveal that the composite slag solidifying agent can substantially improve the unconfined compressive strength of Caofeidian’s saline dredger fill by imparting a good microstructure: a compact overall structure was obtained and few voids were observed in the solidified soil. The optimal proportion was determined as 10% slag + 1.0% quicklime + 0.8% sodium silicate + 1.5% gypsum powder. In addition, the composite slag solidifying agent can effectively reduce the content of soluble salts in saline dredger fill and substantially improve the engineering characteristics of solidified soil.