磷石膏粒径对湿拌砂浆性能及微观结构的影响研究

选取四种不同粒径磷石膏,分别与机制砂、水泥及外加剂混合制备了湿拌砂浆,考察了磷石膏粒径对砂浆工作性及力学性能的影响,并通过XRD、TG-DSC、MIP以及SEM测试探究了磷石膏粒径对湿拌砂浆水化产物及微观结构的影响机理。结果表明,随着磷石膏粒径增大,湿拌砂浆工作性及力学性能呈先增大后减小的趋势,当掺入30%(质量分数)粒径为53~106 μm的磷石膏时,湿拌砂浆稠度损失19%,保水率为90%,28 d抗压强度为10.7 MPa,14 d拉伸黏结强度为0.25 MPa,可满足抗压强度大于10 MPa的技术指标要求。随着磷石膏粒径增大,磷石膏中的共晶磷含量减少,水泥水化过程受抑制程度减弱,砂浆中水化硅酸钙(C-S-H)生成量增多,且在远离CaSO₄·2H₂O颗粒的区域有大量C-S-H出现。然而,砂浆硬化体的孔体积却呈先减小后增大的趋势,当掺入30%(质量分数)粒径为53~106 μm的磷石膏时,砂浆的孔体积最小,仅为0.130 9 mL/g。磷石膏粒径范围适宜控制在53~106 μm,此时湿拌砂浆具有良好的工作性及力学性能。

Influence of Phosphogypsum Particle Size on Properties and Microstructure of Wet-Mixed Mortar

Four kinds of phosphogypsum with different particle sizes were selected and mixed with mechanical sand, cement and admixtures to prepare wet-mixed mortar. The effects of phosphogypsum particle size on the workability and mechanical properties of mortar were investigated, and the mechanism of phosphogypsum particle size on the hydration products and microstructure of wet-mixed mortar was investigated by XRD, TG-DSC, MIP and SEM test. The results show that with the increase of phosphogypsum particle size, the workability and mechanical properties of wet-mixed mortar show a trend of increase first and then decrease. When 30% (mass fraction) phosphogypsum with particle size of 53~106 μm is added, the wet-mixed mortar consistency loss is 19%, water retention rate is 90%, 28 d compressive strength is 10.7 MPa, 14 d tensile bond strength is 0.25 MPa, which can meet the requirements of compressive strength greater than 10 MPa. With the increase of phosphogypsum particle size, the eutectic phosphorus content in phosphogypsum decreases, the hydration process of cement is inhibited to a lesser extent, the calcium silicate hydrate (C-S-H) generated in mortar increases, and a large amount of C-S-H appears in the region away from CaSO₄·2H₂O particles.However, the pore volume of mortar hardening body shows a trend of decrease first and then increase, when 30% (mass fraction) phosphogypsum with particle size of 53~106 μm is added, the pore volume of mortar is the smallest, only 0.130 9 mL/g. Phosphogypsum particle size range is suitable to be controlled in 53~106 μm, at this time, the wet-mixed mortar has good workability and mechanical properties.