针对碱当量为0.10%的低碱硅酸盐水泥熟料出现石膏不能缓凝甚至促凝的异常现象,通过补充碱金属硫酸盐并与碱当量为0.64%的熟料进行对比,测定水泥凝结时间、流动度和黏度的变化,同时采用水化微量热仪和X射线衍射仪测量水化热和分析水化产物,以反映碱金属硫酸盐在低碱水泥早期凝结过程中的作用。结果表明:对于低碱熟料,外掺石膏使水泥SO_3含量达到0.50%,水泥初凝时间显著缩短,继续增加石膏掺量初凝时间虽有一定延长,但仍短于未掺石膏的熟料。碱金属硫酸盐有利于延长水泥凝结时间,但与水泥碱硫比即Na_2O_e/SO_3摩尔比有关,低于0.30时石膏缓凝作用不明显,高于0.60时继续增加碱含量会引起凝结异常,因此Na_2O_e/SO_3摩尔比在0.30~0.60范围内有利于凝结时间延长。适量碱金属硫酸盐能促进石膏与3CaO·Al_2O_3(C_3A)反应,有利于石膏发挥缓凝作用。 Aiming at the abnormality that gypsum can not retard or even procoagulant in low alkali Portland cement clinker with base equivalent of 0.10%, by comparing the alkali metal sulfate with the alkali equivalent of 0.64% clinker, the cement setting time , Fluidity and viscosity. The hydration calorimeter and X-ray diffractometer were used to measure the hydration heat and analyze the hydration products to reflect the role of alkali metal sulfate in the early setting process of low alkali cement. The results show that for the low alkali clinker, the content of SO_3 reaches 0.50% with the addition of gypsum, the initial setting time of cement is significantly shortened, and the initial setting time of gypsum dosage is prolonged, but it is still shorter than that without gypsum . Alkali metal sulphate can prolong the setting time of cement, but it is related to the alkali-sulfur ratio of cement, ie, the molar ratio of Na_2O_e / SO_3. When the ratio is below 0.30, the retarding effect of gypsum is not obvious. If it is higher than 0.60, it will cause abnormal coagulation. Na2Oe / SO3 molar ratio in the range of 0.30 ~ 0.60 is conducive to the condensation time extension. The appropriate amount of alkali metal sulfate can promote the reaction of gypsum with 3CaO · Al_2O_3 (C_3A), which is good for the retarding effect of gypsum.