柠檬酸对石膏析晶过饱和度和微结构的影响

利用SEM扫描电镜、MIP压汞测孔技术和原子吸收光谱等测试手段，系统研究了柠檬酸对建筑石膏水化进程、液相离子浓度与过饱和度、二水石膏晶体形貌、硬化体结构的影响。结果表明：柠檬酸是建筑石膏的高效缓凝剂，它使建筑石膏水化进程减慢，水化诱导期延长，早期水化率降低；柠檬酸使早期液相离子浓度和过饱和度降低，使二水石膏晶体尺度增大，并改变二水石膏晶体生长习性，使晶形由针状转变为短柱状；柠檬酸使石膏硬化体大孔增加，孔径分布粗化。

Effect of Citric Acid on Crystalline Habit and Crystal Morphology of Dihydrate

In this paper,by using scanning electric microscope(SEM),mercury intrusion porosimetry(MIP),and atom adsorption spectrophotometer,the effect of citric acid on the hydrate process,ion concentration in liquid phase and supersaturation degree,crystal morphology of dehydrate,and microstructure of hardened paste of building gypsum were systemically studied.The results indicated that citric acid was high efficiency retarded of building gypsum,which slowed down the hydration process of building gypsum,leading to prolong of the inducing period and decrease of hydration ratio at early stage.Addition of citric acid decreases ion concentration in liquid phase and supersaturation degree and changes the crystalline habit of dehydrate,lead to large crystal size and transformation of crystal shape from need-like to short prismatic.After addition of citric acid,the large pore fraction in hardened gypsum paste was increased and the pore size distribution was coarsened.