Chemical Composition of Phosphogypsum.

The resource utilization of phosphogypsum has been a worldwide problem. Previous research was limited to mixing phosphogypsum with other materials (lime, gravel, red clay) to play an auxiliary role rather than being the main part, the utilization rate is low. This study aims to assess the deformation and crack behavior of cement-stabilized phosphogypsum under varying environmental conditions, and provide theoretical basis for the application of cement-stabilized phosphogypsum materials in road engineering. The test results showed that, firstly, the absolute expansion and absolute shrinkage of cement-stabilized phosphogypsum materials increased with the increase of compaction, cement dosage and the number of wet and dry cycles, and decreased with the increase of initial water content and the dosage of phosphogypsum; Secondly, the fracture rate of cement-stabilized phosphogypsum materials increased with cement dosage and the number of wet and dry cycles; and decreased with compaction, initial moisture content, and phosphogypsum dosage; Thirdly, the relationship between the absolute expansion or shrinkage of cement-stabilized phosphogypsum materials and the compaction degree and the fracture rate is not a simple linear relationship, but is affected by a combination of factors, showing nonlinear characteristics, which can be fitted by the nonlinear binary quadratic equation f(x,y) =ax2+bx+cy2+dy+e. The compaction degree and the fracture rate are the key factors influencing the material’s volume change, while the absolute expansion or shrinkage is a quantitative indicator of the volume change of the material under specific environmental conditions. Fitting by a nonlinear quadratic equation can effectively capture the complex nonlinear relationship between the variables and provide more accurate fitting results, and by analyzing the extreme points of this equation, the optimal degree of compaction can be determined to maximize the material properties.

磷石膏资源化利用一直是世界性难题。既往研究多局限于将磷石膏与石灰、碎石、红黏土等其他物料混合，仅作为辅助掺料而非主体材料，导致整体利用率偏低。本研究旨在评估不同环境条件下水泥稳定磷石膏的变形与开裂行为，为水泥稳定磷石膏材料在道路工程中的应用提供理论依据。试验结果表明：其一，水泥稳定磷石膏材料的绝对胀缩量随压实度、水泥掺量及干湿循环次数的增加而增大，随初始含水率及磷石膏掺量的增加而减小；其二，该材料的开裂率随水泥掺量、干湿循环次数的增加而升高，随压实度、初始含水率及磷石膏掺量的增加而降低；其三，水泥稳定磷石膏材料的绝对胀缩量与压实度、开裂率之间并非简单的线性关系，而是受多因素共同影响，呈现非线性特征，可通过非线性二元二次方程$f(x,y)=ax^2+bx+cy^2+dy+e$进行拟合。压实度与开裂率是影响该材料体积变形的关键因素，而绝对胀缩量则是特定环境条件下材料体积变化的量化表征指标。通过非线性二次方程拟合可有效捕捉变量间复杂的非线性关联，获得更为精准的拟合结果；通过对该方程极值点的分析，可确定最优压实度以最大化材料性能。