Application of Phosphogypsum‐Based Modified Materials in Road Engineering of China

To determine the research status of phosphogypsum‐based materials in Chinese road engineering, this article introduces the physicochemical properties of phosphogypsum materials, analyzes its strength formation mechanism, and evaluates its road performance. Moreover, the pretreatment methods and environmental impact of phosphogypsum application in Chinese road engineering were summarized. It can be clearly stated that the phosphogypsum is a low‐strength material that has poor water stability; however, when compounded with cement or other materials, stabilized phosphogypsum exhibits significantly improved water stability, strength, and overall road performance. On the one hand, ettringite (AFt) and calcium silicate hydrate (C–S–H) were formed via cement hydration to provide strength. On the other hand, phosphogypsum reacts chemically with cement hydration products to generate AFt, which can further enhance the strength of the stabilized materials. In addition, research on phosphogypsum materials is mostly focused on experimental roads and has not yet been widely applied to road engineering on a large scale. The performance of most experimental roads showed that the bearing capacity and compaction of the base course or subgrade constructed by the phosphogypsum‐based modified materials can meet the Chinese standards; therefore, it can be applied for road engineering from the perspective of road performance. However, most studies only utilized phosphogypsum in small quantities, whereas the application of phosphogypsum at high contents in road engineering remains to be further investigated. Moreover, phosphogypsum‐based materials tend to agglomerate into clumps, which can easily clog mechanical mixing equipment. Therefore, it is urgent to develop dedicated mixing equipment for such materials in road engineering. Additionally, common pretreatment methods for phosphogypsum, such as washing, lime neutralization, and flotation, can be used to remove impurities like phosphorus and fluorine. Furthermore, various curing agents have been developed for stabilizing the harmful substances.