轻质抹灰磷建筑石膏性能影响机制研究

采用磷建筑石膏(PBG)、柠檬酸钠(SC)、甲基纤维素(MC)及玻化微珠为原料制备轻质抹灰石膏,并系统地分析了外加剂、轻集料对砂浆性能的影响机制。结果表明,柠檬酸钠可增大砂浆的流动性能, 当掺量为0.8%(掺量均为质量分数)时,样品抗压强度达到16.3 MPa。然而,甲基纤维素降低了砂浆的流动性能,当掺量为0.40%时,样品抗压强度仅为11.3 MPa。玻化微珠会降低砂浆密度及流动性,缩短凝结时间,增大了保水率及硬化体拉伸粘结强度。采用95%磷建筑石膏、5.0%玻化微珠并按磷建筑石膏质量外掺1.0%SC、0.20%MC配制的砂浆样品性能可达到GB/T 28627—2012《抹灰石膏》中的轻质抹灰石膏性能的要求。随着SC掺量的增加,轻质抹灰石膏水化产物二水石膏的形貌向长条、针状转变,晶体结晶度降低、搭接程度增大,从而使得抗折强度增大,抗压及拉伸粘结强度减小;随着MC掺量的增加,轻质抹灰石膏水化产物二水石膏的形貌变成厚板状,晶体间搭接程度及结晶度增大,使得硬化强度增大。

Performance Influence Mechanism of Lightweight Plastering Phosphorus Building Gypsum

Light gypsum plaster was prepared by using phosphorus building gypsum (PBG), sodium citrate (SC), methyl cellulose (MC) and vitrified microsphere as raw materials. The influence mechanism of admixtures and lightweight aggregates on mortar properties was systematically analyzed. The results show that sodium citrate improves the fluidity of mortar, and the compressive strength of the sample reaches 16.3 MPa when the content of sodium citrate is 0.8% (all the content are mass fraction). However, the fluidity of the mortar is reduced by methylcellulose, and the compressive strength of the sample is only 11.3 MPa when the content is 0.40%. The density of the mortar added with vitrified microsphere decreases, and the fluidity and setting time of the mortar also decrease. The water retention rate and tensile adhesive strength of hardened body increase. When 95% phosphorus building gypsum, 5.0% vitrified misrosphere are used and 1.0%SC and 0.20%MC are added by according to the quality of PBG, the properties of the mortar samples can meet the requirements of lightweight plaster gypsum properties in GB/T 28627—2012 “gypsum plaster”. With the increase of SC content, the morphology of dihydrate gypsum, which is the hydration product of lightweight plastering gypsum, changes to long strip and needle shape. The crystal crystallinity decreases and the overlapping degree increases, which makes the flexural strength increase, the compressive strength and tensile adhesive strength decrease. With the increase of MC content, the morphology of dihydrate gypsum, which is the hydration product of lightweight plastering gypsum, becomes thick plate, the degree of overlapping between crystals and crystallinity increases, which makes the hardening strength increase.