Effect of storage temperature on the cementitious property of hemihydrate phosphogypsum
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摘要: 半水磷石膏(HPG)長時間堆存狀態下會出現固結現象,其膠凝性能也相應下降。以室內HPG結晶水檢測和單軸壓縮試驗為基礎,通過設定4種不同堆存溫度,分別為20,40,60和80 ℃,探究不同堆存溫度作用下HPG試樣結晶水質量分數變化和堆存后制備的充填膠凝材料(HCM)抗壓強度發展規律,并采用掃描電鏡等微觀分析手段研究堆存溫度對其強度影響機制。結果表明,堆存溫度對HPG膠凝性能影響顯著,高的堆存溫度會加快HPG試樣中的自由水轉變為結晶水速率,而且會抑制堆存后制備的HCM強度發展。采用數據標準化對不同堆存溫度作用后的試樣抗壓強度作出預測,被證實與實測值較吻合。微觀分析發現,堆存溫度主要影響體系的過飽和度,而使不同堆存溫度作用后制備的HCM微觀形態表現差異。Abstract: Whether domestic or foreign, the utilization of phosphogypsum (PG) resources is not satisfactory. A chemical plant in Guizhou produces phosphoric acid through a semi-aqueous process to obtain the byproduct hemihydrate phosphogypsum (HPG), which has a certain gelling activity. If this feature of HPG can be fully utilized, it can replace cement as a cementing material to prepare mine-filling materials. Utilizing HPG for goaf filling can not only reduce the environmental protection problems caused by the surface discharge of PG but also eliminate the hidden safety hazards in the goaf. At present, when HPG is used to prepare mine-filling cementitious materials, HPG will be consolidated into a block and lose its gelling activity when it is stacked for a certain period of time. The gelling performance of the HPG in the storage state appears to decline. Based on the indoor HPG crystal water detection and uniaxial compression test and setting four different storage temperatures (20 ℃, 40 ℃, 60 ℃, and 80 ℃), this study explored the changes in the mass fraction of the crystal water of HPG samples under different storage temperatures. The compressive strength development law of HCM prepared after storage and microscopic analysis methods, such as scanning electron microscopy, were used to study the influence mechanism of the storage temperature on its strength. Results show that the stacking temperature has a significant effect on the gelling performance of HPG. A high stacking temperature will speed up the conversion of free water in the HPG sample to crystal water and inhibit the strength development of the HCM prepared after stacking. Data standardization was used to predict the compressive strength of samples after storage at different temperatures, which is confirmed to be in good agreement with the measured values. The microscopic analysis found that the storage temperature mainly affects the supersaturation of the system, and the microscopic morphology of the HCM prepared after storage at different temperatures is different.
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表 1 HPG化學成份及含水率測定結果表(質量分數)
Table 1. Hemihydrate phosphogypsum’s chemical composition and moisture content
% CaO Al2O3 SiO2 P2O5 MgO Fe2O3 SO3 SrO loss Free water Crystal water 37.86 2.46 4.20 1.37 0.28 0.45 44.82 0.36 0.20 22.10 5.40 www.77susu.com -
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