改性磷石膏作水泥缓凝剂的研究

Study on modification of phosphogypsum as cement retarder

为将磷石膏应用于水泥缓凝剂,采用水洗等方式对磷石膏进行预处理。确定水洗磷石膏的最优用水量和水洗时间。对比研究天然石膏、原状磷石膏和改性磷石膏对硅酸盐水泥凝结时间和强度的影响。通过水化热、XRD和SEM分析改性磷石膏对硅酸盐水泥水化特性的影响机理。结果表明,磷石膏在液固比为4和水洗时间为25 min条件下水洗效果最佳;生石灰单掺以及生石灰和膨润土复掺对磷石膏中可溶性磷和可溶性氟表现出较好的固化效果;水洗改性后磷石膏可有效缩短水泥的凝结时间,提高早期强度,其中生石灰与膨润土按2∶1复掺水洗改性后磷石膏用于硅酸盐水泥,水泥初、终凝时间比使用原状磷石膏时缩短了50%和31%;改性磷石膏制备的水泥早期水化速率正常,水泥固结体结构致密,缺陷较少,早期强度高。

To apply phosphogypsum as a cement retarder,pre-treatment of phosphogypsum is carried out by water washing and other methods.Determine the optimal water consumption and washing time of water-washed phosphogypsum.The effects of natural gypsum,as-built phosphogypsum and modified phosphogypsum on the setting time and strength of silicate cement were compared and investigated.The effect mechanism of modified phosphogypsum on the hydration characteristics of silicate cement was analyzed by heat of hydration,XRD and SEM.The results showed that phosphogypsum has the best water washing effect under the conditions of liquid-solid ratio of 4 and washing time of 25 minutes,the compounding of quicklime,quicklime and bentonite showed better curing effect on soluble phosphorus and soluble fluorine in phosphogypsum;the washed modified phosphogypsum could effectively shorten the setting time and improve the early strength of cement,in which the washed modified phosphogypsum with quicklime and bentonite compounded at 2∶1 was used for silicate cement,the initial setting time and final setting time of cement were shortened by 50%and 31%compared with the original phosphogypsum.The early hydration rate of cement prepared by modified phosphogypsum is normal,the cement solidification body structure is dense,with fewer defects and high early strength.