以磷石膏为原料,分别采用煅烧法和常压酸化法制备磷Ⅱ型无水石膏,通过物相组成、微观形貌、化学组成及粒径分布,分析比较了两种方法制备的磷Ⅱ型无水石膏的差异性.在激发剂明矾不同掺量下,分析比较不同制备方法对磷Ⅱ型无水石膏的凝结时间、硬化体强度及水化率的影响.结果表明:由煅烧法制得的磷Ⅱ型无水石膏AH-1的微观形貌呈菱形,由常压酸化法制得的磷Ⅱ型无水石膏AH-2的微观形貌呈矩形,其中AH-2结晶度及纯度高、平均粒径小、比表面积大;当未掺明矾时,无水石膏水化硬化缓慢,终凝时间在35 h以上,28 d水化率在30%左右;当明矾质量分数为1%时,AH-1的终凝时间由40 h 20 min缩短至5 h 40 min,AH-2的终凝时间由35 h 20 min缩短至4 h 20 min,28 d抗压强度分别为空白组的2.54倍和3.01倍;随着明矾掺量的增加,AH-1和AH-2的性能差异逐渐减小,AH-1和AH-2的终凝时间相差在30 min以内,28 d抗压强度均为空白组的3.2倍.同时,AH-2水化生成的二水石膏表面光滑,搭接更加致密.通过比较可知,常压酸化法制备磷Ⅱ型无水石膏工艺更具优势.
Study on hydration properties of type Ⅱ anhydrite prepared by calcination and atmospheric acidification
Type Ⅱ anhydrite was prepared by calcination method and atmospheric acidification method using phosphogyp-sum as raw material.The differences of type Ⅱ anhydrite prepared by the two methods were analyzed and compared through the analysis of phase composition,micro-morphology,chemical composition and particle size distribution.The effects of dif-ferent preparation methods on the setting time,hardening strength and hydration rate of type Ⅱ anhydrite were analyzed and compared under different dosage of alum.The results showed that the microstructure of type Ⅱ anhydrite AH-1 pre-pared by calcination was diamond shaped,and that of type Ⅱ anhydrite AH-2 prepared by atmospheric acidification was rectangular,in which AH-2 had high crystallinity and purity,small average particle size and large specific surface area.When the anhydrite was not mixed with alum,the hydration hardening was slow,the final coagulation time was more than 35 h,and the hydration rate was about 30%in 28 d.When the alum content was 1%(mass fraction),the final coagulation time of AH-1 was shortened from 40 h 20 min to 5 h 40 min,the final coagulation time of AH-2 was shortened from 35 h 20 min to 4 h 20 min,and the compressive strength of 28 d was 2.54 times and 3.01 times of that of the blank group,respec-tively.With the increase of alum content,the performance difference between AH-1 and AH-2 was gradually decreased.The final coagulation time difference between AH-1 and AH-2 was less than 30 min,and the 28 d compressive strength was 3.2 times that of the blank group.At the same time,the surface of the dihydrate gypsum produced by AH-2 hydration was smooth and the bonding was more dense.By comparison,it could be seen that the preparation process of type Ⅱ anhydrite by atmospheric pressure acidification was more advantageous.
万方数据
维普
