液态无碱速凝剂的性能及其作用机理

摘要

介绍了一种新型无碱液态速凝剂的合成方法，并采用宏微观试验对其性能及作用机理进行研究。结果表明：当速凝剂掺量为8%时，可使P·O 42.5级水泥的初凝时间和终凝时间缩短至180、410 s，1 d抗压强度达到23.4 MPa，比空白样提高了36.2%，28 d抗压强度保有率达到了110%；速凝剂对材料温度变化不敏感，其在低温下仍具有良好的促凝效果；但增大了水泥砂浆的收缩，需对其合理养护；通过SEM测试手段分析了其促凝机理：在早期水泥浆体水化过程中，形成大量的钙矾石晶体，晶体间相互搭接，形成空间骨架结构，导致水泥浆体迅速凝结。%Presented a alkali-free liquid setting accelerator and properties of the production process such as technical characteristics.Re-sults of property test showed that 8%alkali-free liquid setting accelerator addition could shorten initial setting time and final setting time of P·O 42.5 to 180 s and 410 s respectively,made 1 d compressive strength attain to 23.4 MPa which was 36.2%higher than that of blank specimen,retaining rate of 28 days compressive strength reach 110%.The setting accelerator is insensitive to the change of material temper-ature,had good accelerate effect in low temperature,but increased the shrinkage of cement paste,and need appropriate maintenances.The acceleration mechanism was analysised through the test method of SEM.At the beginning hydration ,the cement paste with liquid setting accelerator produced a mass of clubbed ettringite crystal,the overlap between the crystal forms the space frame structure,which is the main reason of improving the cement paste setting.