Utilization of flue gas desulfurization gypsum to produce green binder for dredged soil solidification: Strength, durability, and planting performance

Abstract

The massive deposition of sediment in the Yellow River leads to the waste of land resources and is also prone to environmental disasters. In this study, the industrial by-product, flue gas desulfurization gypsum (FGDG), was incorporated with Portland cement (PC) and fly ash (FA) to treat the dredged soil (DS) from the Yellow River. The effects of initial water content of DS (w0), binder content (Aw), and the FGDG content in binder on the strength development and durability of solidified dredged soil (SDS) were analyzed via a series of UCS, pH value, and dry-wet cycles tests. Additionally, the planting performance of SDS was evaluated by planting wheat grass, and the microstructure characteristics were conducted by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, and scanning electron microscope (SEM) method. The results indicate that, when the binder containing 50% FGDG, the SDS sample has good strength and resistance to dry-wet cycles, and decreasing w0, increasing Aw, or reducing the FGDG content in binder can obviously improve the strength and durability of SDS. Furthermore, increasing the FGDG content in binder is more beneficial to germination and growth of plants. The micro-analysis shows that, during the dry-wet cycles test, the amount of hydration products (i.e., C–S–H and AFt) in SDS increased significantly, and the structure became denser, resulting in the increase of strength. During planting, the pH of SDS decreased rapidly to about 8.5, mainly because the root respiration accelerated the carbonization of Ca(OH)2 crystals in sample.