The Relationship Between Flowability Of Concrete With Differeiit Types Of Superplasticizer And Rheological Parameters Of Mortar

High-performance is the development tendency of modern concrete technology, and theexcellent workability is primary for the construction of concrete structures. Liquidity is animportant indicator of the performance, which has a direct impact on the construction and thequality of concrete, indicating the consistency of the mixture. So the study of the liquidity ofconcrete, particularly the liquidity of slurry in the concrete becomes more and moreimportant.From the view of rheology, most of concrete fluidity test methods aresingle-point-method and not perfect. The most direct course for the study of the rheologicalproperties of fresh concrete is through the test with concrete testing, but the stability andreproducibility of results is poor due to the impact of coarse aggregate, and completelythrough with concrete testing costs a lot of manpower and material resources. Therefore, it iseasier to use the measured yield stress and plastic viscosity of mortar to reflect thecorresponding values of the fresh concrete.The research of the performance of concrete shows that good fluidity requires a lowyield stress and plastic viscosity. On the other hand, concrete mixture must also bemaintained homogeneous during the construction process, which needs a large yield stressand plastic viscosity to get enough anti-separation ability and avoid mixing segregation orbleeding. So for high-fluidity concrete, not unilaterally pursuit the yield stress and the plasticviscosity as low as possible to obtain large flowing ability, but only has to meet theconstruction requirements of the fluidity of concrete in a suitable range, but also has goodcohesiveness and water retention, avoiding segregation or bleeding of mixture in the processof transportation, parking, pouring, tamping. Evaluating the working performance of concretefor different performance requirements, with the physical parameters of rheologicalquantitatively, can optimize proportions of concrete mix and the use of different types ofsuperplasticizer.This paper carried out a lot of work on low-grade concrete with good pumpingperformance from the actual project, and identified a reasonable range of mortar rheologicalparameters.The result shows that: the range of the yield stress and plastic viscosity of mortar of pumping concrete with naphthalene superplasticizer: C25strength grade:8.35~15.48Pa,1.26~2.32Pa s; C30strength grade:9.13~15.34Pa,1.63~2.56Pa s; C35strength grade:15.75~18.69Pa,2.03~2.95Pa s. And the range of the yield stress and plastic viscosity ofmortar of pumping concrete with polycarboxylate superplasticizer: C25strength grade:8.82~10.48Pa,1.12~1.36Pa s; C30strength grade:9.84~14.87Pa,1.75~2.38Pa s.The study of the influence of different types of superplasticizer on rheologicalparameters of mortar shows that, when all the mortar water reduction rate of different typesof superplasticizer is40%, the law of the influence on rheological parameters of mortar, theyield stress: low concentrated naphthalene> highconcentrated naphthalene> acetone> esterspolycarboxylate> ethers polycarboxylate; the plastic viscosity: low concentratednaphthalene> acetone> highconcentrated naphthalene> ethers polycarboxylate>esterpolycarboxylate. Compared with naphthalene superplasticizer, polycarboxylatesuperplasticizer reduces the yield stress and plastic viscosity of mortar more significantly.The law shows that concrete preparation technology with naphthalene superplasticizer orpolycarboxylate superplasticizer is different. For low grade concrete with polycarboxylatesuperplasticizer,we can improve the yield stress and plastic viscosity of mortar by reducingthe water-binder ratio to prevent bleeding and segregation.