Research on strength characteristics and mechanism of cement stabilized phosphogypsum materials under dry and wet cycles

Phosphogypsum can be used for mine filling, ecological restoration materials, road construction materials, soil conditioning agent, cement retarder, etc., the comprehensive utilization rate of only about 40%, less than 10% for road construction materials, for the huge demand for raw materials road projects, obviously a drop in the bucket. In order to solve the accumulation problem of phosphogypsum, this paper closely combines the major needs of national highway construction, actively responds to the call of Guizhou Provincial People's Government and Guiyang Municipal People's Government on the comprehensive utilization of phosphogypsum resources, and researches the strength decay law of cement-stabilized phosphogypsum materials under dry-wet cycle, considering the complex climatic characteristics of dry-wet cycle with the prerequisite of high phosphogypsum mixing, and reveals the mechanism of strength decay, and establishes a strength regression model, and discusses the suitability as pavement base (sub-base) materials. The strength regression model was established, and the suitability of cement stabilized phosphogypsum as the base layer (sub-base layer) of pavement was discussed. The results show that the unconfined compressive strength of cement-stabilized phosphogypsum material decreases with the increase of the number of dry and wet cycles, and the decay is faster in the first four dry and wet cycles, and then gradually tends to level off. The unconfined compressive strength and the number of wet and dry cycles can be fitted with a negative exponential function, and the fitting parameters are all greater than 0.98 . Cement dosage had the most significant effect on unconfined compressive strength with F-value = 988.407, followed by the number of wet and dry cycles and compaction had the least effect. The maximum values of RMSE and MAE were 0.0862 and 0.0776 for the multifactorial regression equation of the unconfined compressive strength of cement-stabilized phosphogypsum materials, which indicated that the regression model had a high reliability. Through the research in this paper, cement stabilized phosphogypsum materials can be used as the base layer (sub-base layer) for highway pavements of various grades under different cement mixing amounts and different traffic volume conditions.