三聚氰胺减水剂对α半水石膏水化硬化过程的影响

Effects of sulfonated melamine formaldehyde on the setting of α-calcium sulfate hemihydrates.

采用高磺化度三聚氰胺(Sulfonated melamine formaldehyde,SM)改良α半水石膏使用性能,研究了减水剂对石膏水化硬化过程的影响.首先测定了SM对α半水石膏的减水效率,然后通过强度测试、热重分析和电镜扫描,揭示了SM对α半水石膏强度发展过程、水化速度及硬化体亚微观结构的影响.结果表明,SM对α半水石膏的最大减水率为15.6%,对应最佳掺量为0.5%.经SM改性的α半水石膏其强度发展过程发生了变化,且2 h湿抗折和湿抗压强度、绝干抗折和抗压强度分别提高38%、29%、20%和27%.此外,SM能加速α半水石膏的水化,经其改性后的石膏硬化体结构中二水石膏晶体数量增多,长径比明显减小,硬化体结构更为密实.因此,SM可用于改良α半水石膏,特别有利于提高石膏硬化体的强度.

The hydration and hardening processes of α-calcium sulfate hemihydrates（α-HH） based plaster, modified by sulfonated melamine formaldehyde （SM）, were studied and compared with pure plaster. The water-reducing efficiency of SM for α-HH was firstly determined. Then, the impacts of SM on strength development, hydration rate and microstructure of α-HH based plaster were inspected by mechanical strength test, thermogravimetry （TG） and scanning electron microscopy （SEM）. The results showed that the highest water-reducing efficiency was 15.6 and the optimized dosage was 0. 5 %. SM influenced the strength development of plaster. The strength of SM modified α-HH was raised by 38%, 29%, 20%, 27% for 2 h bending strength, 2 h compressive strength, the dry bending strength and dry compressive strength, respectively. SM accelerated the hydration of α-HH. The dehydrate （DH） crystals were increased and changed into column or board forms by SM, leading to more impact structure. Therefore, SM is suitable for α-HH modification, especially in improving the mechanical strength.