Hi this thesis , the setting time of various retarders had been tested , in which three retarders with good retarding action , citric acid , sodium tripolyphosphate , bone glue are respectively chosen from three types of retarders , hydroxyl carboxylic acid type , phosphate type and protein type , and the strength and setting time of gypsum added with them are determined . effect of some factors , such as ph value , fineness of hemihydrate , type of gypsum on the retarding action of the retarders is also studied 本文对多种缓凝剂进行凝结时间测试，选择效果良好的羟基羧酸、无机盐和蛋白质类型的三种缓凝剂：柠檬酸、多聚磷酸钠和骨胶，测定它们对石膏凝结时间、强度等宏观性能的影响，并分别研究ph值、石膏细度和石膏种类等因素对它们的缓凝效果的影响。
As a kind of cement retarder , normal setting time and good effect for mechanical properties and soundness of cement can be got when adding desulfurization gypsum in cement , so it can used instead of natural gypsum to produce cement entirely , coal gangue is activated and coal ash desulfurized have good active , can improve cement output and also can depress consumption when them be used as mixed material , have well economic and environmental effects 脱硫石膏作水泥缓凝剂时，水泥的安定性、凝结时间正常，可改善水泥的力学性能，完全可替代天然石膏；活化后的煤矸石和脱硫煤灰具有较好的活性，用作水泥混合材可增加水泥产量、降低生产成本，具有良好的经济和环境效益。
The expansion agents can only make up the shrinkage to some extent , and the compensation effects would be reduced when the retardener and fly - ash are used . the expansion agents are not panaceas to avoid the shrinkage cracking as expansion can also reduce the concrete soundness . under bad curing condition , the polypropylene fibrillated film fiber can improve concrete ' s anti - crarking property , while the nominal steels have very unobvious effects . to reduce the concrete shrinkage thus avoid the cracking , the former factors must all be taken into account in concrete proportion design to develop sound concrete 研究结果表明，水泥的品种和用量是影响混凝土收缩值的主要因素之一，当混凝土中水泥用量超过470kg / m ~ 3时，混凝土的收缩值超过400 10 ~ ( - 6 ) ，在约束状态下存在高开裂风险；采用细砂使混凝土单位用水量显著提高，收缩值也大幅增加；优质粉煤灰总体上能抑制混凝土的收缩，以超量方式掺入其抑制作用更加明显，但粉煤灰混凝土早期的粘聚性较差，应注意养护，以免失水产生龟裂；早强减水剂和缓凝减水剂都会使混凝土收缩值增加；膨胀剂只能补偿混凝土部分收缩，同时受缓凝剂和粉煤灰的抑制，而且膨胀使混凝土的体积安定性增加了不确定因素，膨胀剂不是解决混凝土收缩裂缝的良方。
The influence of retarder on the seaing time and ultimate strength of gypsum plaster was investigated in this paper . the experimental results indicate that the effect of single retarder , such as citric acid , is inferior to that of composite retarder which was made of blending citric acid with a few portland cement ( about 0 . 5 ? , by weight ) . the effect of different water - retention agents , such as polyvinyl alcohol ( pva ) , carboxymethyl cellulose ( cmc ) , and na - bentonite , etc . , was also studied , and the results demonstrate that by means of adding organic and inorganic water - retention agent simultaneously the water - retention of plastering slurry can obviously be improved . the optimal mix proportion of gypsum plaster suitable to finish coat of walls and ceilings of buildings has been got by use of factorial experiment with orthogonal array accounting for interactions between factors each other 研究了分别以柠檬酸、柠檬酸与普通硅酸盐水泥复合物作缓凝剂,调节粉刷石膏的凝结时间,并对比2种缓凝体系对石膏抗折、抗压强度的影响.比较不同保水剂(聚乙烯醇、羧甲基纤维素)以及相同量的保水剂在不同工艺流程下保水效果上的区别.探索了有机保水剂和无机保水剂对粉刷石膏的保水性的影响.结果表明,柠檬酸与普通硅酸盐水泥的复合缓凝剂比单纯的柠檬酸更能有效地延缓建筑石膏的凝结,同时建筑石膏的抗折、抗压强度降低幅度减小
