黏度改性剂对混凝土拌和物流变参数及匀质性能影响

Effect of Viscosity Modifier on Rheological Parameters and Homogeneous Performance of Concrete Mixture

通过ICAR流变仪、分层度测试仪和多功能力学试验机,研究了微珠黏度改性剂、复合黏度改性剂及其掺量对混凝土塑性黏度、屈服应力、分层度及力学性能的影响,揭示了微珠黏度改性剂和复合黏度改性剂对大流态新拌混凝土流变特性及匀质性的影响规律,并指出了适量掺入的优点及超量掺入的缺点,最后,结合北京市某工程泵送混凝土的应用情况,提出了可泵送、塑性黏度及分层度的关系。结果表明:掺入微珠黏度改性剂或复合黏度改性剂均能显著降低混凝土拌和物的塑性黏度和屈服应力,且随着它们掺量的增加,屈服应力、塑性黏度及分层度均呈现先减小后增大规律;同掺量下微珠黏度改性剂对混凝土拌和物浆体匀质性的破坏力大于复合黏度改性剂,即分层度大,然而降黏效果相反;当黏度改性剂掺量小于30%时,混凝土28 d抗压强度均大于空白样,但掺量大于30%时,28 d抗压强度均小于空白样。工程应用表明,长距离或高层泵送混凝土,并不是塑性黏度越低越好,而是存在一个合理范围,这个范围使得混凝土拌和物是一个触变性的匀质的黏性混合物,根据应用统计分析,可采用塑性黏度与分层度的交集表示混凝土可泵区间,其表达式为:[(0,塑性黏度)∩(0,分层度)]。

The effects of micro-bead viscosity modifier, compound viscosity modifier and its content on the plastic viscosity, yield stress, stratification and mechanical property of concrete are studied by ICAR rheometer, stratification tester and multifunctional mechanical testing machine. The effect regularity of micro- bead viscosity modifier and composite viscosity modifier on the rheological property and homogeneity of freshwater concrete are revealed, and the advantages of proper incorporation and disadvantages of overweight incorporation are pointed out. Finally, combining with the application of pumping concrete in a project in Beijing, the relationship among pump-ability, plastic viscosity and stratification is put forward. The result shows that （1） the incorporation of micro-bead viscosity modifier or composite viscosity modifier can significantly reduce the plastic viscosity and yield stress of the concrete mixture, and with the increase of their content, the yield stress, plastic viscosity and stratification of the concrete mixture reduces at first and thenincreases; （2） the destructive force of micro-bead viscosity modifier to the homogeneous performance of concrete mixture slurry is higher than that of adding same content of the compound viscosity modifier, that is, the degree of stratification is large, but the viscosity reduction effect is opposite; （3） when the content of viscosity modifier is less than 30% , the compressive strength of concrete is larger than that of blank, but when the content is more than 30%, the 28 d compressive strength is less than 28 days, and vise versa. Engineering applications show that for long-distance or high-level pumping of concrete, not the lower of plastic viscosity the better, but there is a reasonable range, which makes the concrete mixture a thixotropic homogeneous viscous mixture, and according to the applicative statistical analysis, the concrete can be pumped in the intersection of plastic viscosity and stratification, i.e., （0, plastic viscosity ） ∩（0, stratification） ].