无碱液态速凝剂的改性和速凝机理

Improvement of the alkali-free cement setting accelerator and its acceleration mechanism

以无碱液态速凝剂(NSA)为基础,通过对其组成进行优化,从而改善其性能.实验结果表明,改性后,当NSA速凝剂掺量为5%时可使PⅡ52.5硅酸盐水泥的初凝时间缩短至1.5 m in,终凝时间缩短至4.1 m in,1 d抗压强度达到15.9 MPa,比空白试样提高31.4%,28 d抗压强度保留率为92%.使用XRD、SEM、TG-DSC等测试手段对水化试样进行分析,结果表明,改性NSA速凝剂是通过促进形成钙矾石晶体而达到速凝效果的.

The improvement of the performance of the NSA alkali-free setting accelerator for cement was attempted by the the regulation of its chemical composition. The results show that the initial setting time and final setting time of Portland cement added with 5% modified NSA are remarkably shortened to 1.5 min and 4. 1 min respectively, and its 1 d compressive it provides an as high as ture observation on the through the formation of rapid setting. strength reaches 15.9 MPa which is 31.4% higher than the blank cement, and meanwhile 92% retention of 28 d compressive strength. Furthermore, phase analysis and microstruchydrated cement specimens by means of XRD, TG-DSC and SEM revealed that it was ettringite at early age of hydration of cement added with modified NSA that resulted in the