低胶凝材料用量砂浆及混凝土的流变性能

Rheological properties of mortar and concrete with low binder content

在低胶凝材料用量时,研究自流平砂浆流动度与黏度之间的关系以及增黏剂对砂浆流变性能的影响,并在此基础上研究增黏剂对自密实混凝土工作性、力学性能的影响。试验结果显示:自流平砂浆扩展度与黏度间具有很好的负相关性,且两者图线关于某直线对称;增黏剂(CMC、HPMC和硅灰)降低了砂浆扩展度,但黏度增加,改善了砂浆的泌水状况;增黏剂对混凝土工作性的影响与砂浆一致,但存在最佳掺量,使混凝土在大流动性时不发生泌水、离析,提高了其综合性能;增黏剂适用于有泌水、离析的浆体或拌合物时,能够改善其工作性,而应用于无泌水浆体时则会显著降低其流动性。除硅灰具有火山灰活性,能够提高抗压强度外,CMC及HPMC对强度的影响无一致定论,总体上对强度影响不大。

The study was carried on with low content binders and focuses on the relationship between the fluidity and viscosity of self-leveling mortar and also the influence of viscosity modifying admixtures on the rheological properties.On that basis, studied the effect of viscosity modifying admixtures on the fluidity and mechanical properties of self-compacting concrete.Results showed that it had a high inverse correlation between the fluidity and viscosity of self-leveling mortar, and also the two curves were symmetric centered on some straight line.viscosity modifying admixtures including CMC,HPMC and silica fume decreased the fluidity but increased the viscosity and also eliminated the bleeding of mortar.The influence of viscosity modifying admixtures on the concrete was similar to that of mortar,but there was an optimal dosage for viscosity modifying admixtures to make the concrete containing a high fluidity without bleeding or segregation get the excellent integrated performance.viscosity modifying admixtures would improve performances when the mortar or mixture was bleeding or segregation but significantly decreased the workability when they were not.There was no definite conclusion about CMC and HPMC affecting the strength of mortar and concrete except that the silica fume increased the compressive strength for the pozzolanic activity,viscosity modifying admixtures had very little effect on the strength as a whole.