高强大流动度混凝土的制备及应用研究

发布时间：2019-03-02 09:08

【摘要】：本文采用三类流变仪，研究了水泥浆体、砂浆以及混凝土的流变特性。首先，从流变学的角度讨论了颗粒级配对水泥基材料的影响，从而得出了适合制备高强大流动度混凝土的矿物掺合料的最优配合比以及细集料和粗集料的最优级配曲线。水泥基材料流变学研究结果表明，当粉煤灰与矿粉的质量比为2:1，且总量占胶凝材料总质量的30%时，胶凝材料浆体具有较高的流动性和力学性能。与此同时，研究发现一个相对较宽的胶凝材料粒径分布有利于改善浆体的流动性。对砂浆流变性研究结果表明，中砂适合制备普通大流动度混凝土，然而细度模数小于3.30的粗砂更适合制备高强大流动度混凝土。在制备大流动度混凝土时，我们应该更多的去注意各粒径范围内的砂粒质量百分比。一般来说，0.315mm以下的砂粒量百分比在15%-30%之间为宜；0.6mm以下的砂粒质量百分比在30%-45%之间为宜；1.18mm以下的砂粒质量百分比在55%-75%之间为宜。粗集料对流变性能研究结果表明，粗集料的级配对新拌混凝土的流动性影响最大，而对混凝土力学性能影响较小。当制备高强大流动度混凝土时，粒径在4.75mm-9.5mm之间的粗集料质量百分比在30%-50%之间为宜；粒径在16mm-19mm之间的粗集料质量百分比在20%-30%之间为宜。在混凝土流动性要求不是很高的情况下，粒径在16mm-19mm之间的粗集料质量百分比可以放宽到10%-40%。在前期大量试验的基础上，制备了符合工程要求的C60和C80泵送混凝土以及C80自密实混凝土。最后，通过流变仪测试C80泵送混凝土和C80自密实混凝土的流变参数。试验发现，粗集料的砂浆包裹层厚度是引起C80泵送混凝土和C80自密实混凝土流变性差异的主要原因。当砂浆包裹层厚度大于2mm时，自密实混凝土具备良好的流动性和密实效果。如果C80泵送混凝土的粗集料的砂浆包裹层厚度超过2mm，C80泵送混凝土也具有一定的自密实能力，但是它的流动性能很大程度上取决于粗集料的最大粒径。
[Abstract]:In this paper, the rheological properties of cement paste, mortar and concrete are studied by three kinds of rheometer. Firstly, the influence of particle size on cement-based material is discussed from the point of view of rheology, and the optimal mix ratio of mineral admixture suitable for preparing high strength fluidity concrete and the optimal gradation curve of fine aggregate and coarse aggregate are obtained. The rheological study of cement-based materials shows that when the mass ratio of fly ash to mineral powder is 2? 1 and the total amount is 30% of the total mass of cementitious materials, the cement paste has higher fluidity and mechanical properties. At the same time, it is found that a relatively wide particle size distribution of cementitious material is beneficial to improve the fluidity of slurry. The rheological behavior of mortar shows that medium sand is suitable for preparing ordinary high fluidity concrete, but coarse sand with fineness modulus less than 3.30 is more suitable for preparing high mobility concrete. When preparing high fluidity concrete, we should pay more attention to the percentage of sand particles in the range of particle size. Generally speaking, the percentage of sand under 0.315mm is between 15% and 30%; the percentage of sand under 0.6mm is between 30% and 45%; and the percentage of sand under 1.18mm is between 55% and 75%. The results of the study on the convective behavior of coarse aggregate show that the gradation of coarse aggregate has the greatest influence on the fluidity of fresh concrete, but has little effect on the mechanical properties of concrete. When the high strength fluidity concrete is prepared, the mass percentage of coarse aggregate between 4.75mm-9.5mm and 16mm-19mm is between 30% and 50%, and the mass percentage of coarse aggregate between particle size between 20% and 30% is suitable. When the fluidity requirement of concrete is not very high, the mass percentage of coarse aggregate with particle size between 16mm-19mm can be relaxed to 10% and 40%. C60 and C80 pumping concrete and C80 self-compacting concrete were prepared on the basis of a large number of previous tests. Finally, the rheological parameters of C _ (80) pumping concrete and C _ (80) self-compacting concrete were tested by rheometer. It is found that the thickness of mortar envelope of coarse aggregate is the main reason for the difference of rheological properties between C80 pumping concrete and C80 self-compacting concrete. When the thickness of mortar coating is greater than that of 2mm, self-compacting concrete has good fluidity and compacting effect. If the thickness of mortar envelope of coarse aggregate of C80 pumping concrete is more than 2mm, C80 pumping concrete also has certain self-compacting ability, but its flow performance depends largely on the maximum particle size of coarse aggregate.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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