机制砂水泥砂浆流变性能研究

发布时间：2019-05-06 08:42

【摘要】：随着基础设施建设的快速发展和环境保护的加强，河砂资源越来越匮乏，机制砂在混凝土中的应用越来越多。由于机制砂在粒形、级配、石粉含量等方面与河砂存在显著差异，机制砂混凝土与河砂混凝土存在很多不同，其中工作性能的差异最为明显。流变参数是表征水泥基材料流动性能和工作性能的重要指标，描述和控制水泥基材料流变特性，对指导混凝土的工程应用，控制新拌混凝土的工作性能，确保工程质量都具有重要意义。因此，从流变学角度研究机制砂混凝土工作性能具有重要的实用价值和理论意义。总结流变学在混凝土中的应用，内容包括：宾汉姆体在混凝土研究中的应用、触变性及评价方法、水泥浆及新拌混凝土的物理结构、混凝土的工作性等。对比研究不同水灰比下机制砂砂浆与河砂砂浆流变性能，结果表明：相同配合比条件下，机制砂砂浆与河砂砂浆相比，屈服应力较大，塑性粘度较小，流变参数经时变化较大，触变性较小；水灰比越大，河砂砂浆与机制砂砂浆屈服应力、塑性粘度越小，两种砂浆流变参数的差距也逐渐缩小，河砂砂浆与机制砂砂浆流变参数经时变化、触变性越小。研究不同比表面积粉煤灰、聚羧酸高性能减水剂对机制砂砂浆流变性能影响，结果表明：粉煤灰的加入使机制砂砂浆的屈服应力明显降低，塑性粘度增大，且粉煤灰越细越明显；随着粉煤灰掺量的增加，砂浆流变参数经时变化减小，粉煤灰越细效果越明显；粉煤灰掺量小于15%时对机制砂砂浆的触变性无明显影响，粉煤灰掺量大于15%时，比表面积较大的粉煤灰使砂浆触变性减弱，比表面积较小的粉煤灰则使砂浆触变性增大；减水剂的加入使机制砂砂浆的屈服应力降低，，对砂浆塑性粘度的影响较小，机制砂砂浆流变参数经时变化增大，触变性降低。从棱角性、形态学两个角度分析机制砂的粒形特征，并分析机制砂级配与棱角性、比表面积的关系，机制砂级配和石粉含量对砂浆流变性能的影响，结果表明：随粒径和级配的变化，不同岩性机制砂棱角性变化规律基本一致；机制砂圆度随着粒径的减少而减小；随级配变粗，三种岩性的机制砂砂浆屈服应力均先减小后增大，河砂砂浆屈服应力减小；石灰岩机制砂砂浆屈服应力与机制砂棱角性有较好的相关性；随级配变粗，四种细集料砂浆的塑性粘度均下降；河砂砂浆、石灰岩机制砂砂浆塑性粘度与集料比表面积有良好的相关性；从石粉引起砂浆屈服应力增大的角度来讲，机制砂级配越粗，能够容许的石粉含量越高；石粉含量增加，机制砂砂浆塑性粘度增大。
[Abstract]:With the rapid development of infrastructure construction and the strengthening of environmental protection, river sand resources are becoming more and more scarce, and the application of mechanical sand in concrete is more and more. Because there are significant differences between the mechanical sand and the river sand in grain shape, gradation and content of stone powder, there are many differences between the mechanical sand concrete and the river sand concrete, among which the difference of the working performance is the most obvious. Rheological parameters are important indexes to characterize the flow and working properties of cement-based materials. The rheological properties of cement-based materials are described and controlled, which can guide the engineering application of concrete and control the performance of newly mixed concrete. It is of great significance to ensure the engineering quality. Therefore, it is of great practical value and theoretical significance to study the working performance of mechanical sand concrete from the point of view of rheology. This paper summarizes the application of rheology in concrete, including the application of Bingham body in the study of concrete, thixotropy and evaluation method, the physical structure of cement slurry and fresh concrete, the workability of concrete and so on. The rheological properties of mechanical sand mortar and river sand mortar under different water-cement ratios are compared. The results show that under the same mix ratio, the yield stress is larger, the plastic viscosity is small, and the rheological parameters change greatly over time, compared with the river sand mortar under the same mix ratio. Thixotropy is small; The larger the water-cement ratio, the smaller the yield stress and the plastic viscosity of the river sand mortar and the mechanical sand mortar, and the smaller the difference of the rheological parameters between the two mortars. The rheological parameters of the river sand mortar and the mechanical sand mortar change with time, and the thixotropy of the two mortars is smaller. The effects of fly ash with different specific surface area and polycarboxylic acid high performance water reducer on the rheological properties of mechanical sand slurry were studied. The results showed that the yield stress and plastic viscosity of the mortar decreased obviously and the plastic viscosity increased with the addition of fly ash. The finer the fly ash is, the more obvious the fly ash is. With the increase of fly ash content, the rheological parameters of mortar decrease after time, and the finer the fly ash is, the more obvious the effect is. When the content of fly ash is less than 15%, the thixotropy of mortar is not affected obviously. When the content of fly ash is more than 15%, the thixotropy of mortar is weakened by fly ash with larger specific surface area, and the thixotropy of mortar is increased by fly ash with smaller specific surface area. With the addition of water reducing agent, the yield stress of sand mortar is reduced, and the plastic viscosity of mortar is less affected. The rheological parameters of sand mortar are increased and the thixotropy is decreased. The grain shape characteristics of mechanical sand are analyzed from the angles of angularity and morphology, and the relationship between mechanical sand gradation and angularity and specific surface area is analyzed, and the effect of mechanical sand gradation and stone powder content on the rheological properties of mortar is also analyzed. The results show that, with the change of particle size and gradation, the variation rule of sandedges with different lithologic mechanisms is basically the same. The roundness of sand decreases with the decrease of grain size, and the yield stress of sand mortar of three kinds of lithology decreases firstly and then increases, and the yield stress of river sand mortar decreases with the coarsening of gradation. There is a good correlation between the yield stress of limestone sand mortar and the angular property of the sand edge, and the plastic viscosity of the four fine aggregate mortars decreases with the coarsening of gradations, and the plastic viscosity of the four kinds of fine aggregate mortars decreases. There is a good correlation between the plastic viscosity of sand slurry and the specific surface area of aggregate, the thicker the gradation of sand is, the higher the allowable content of stone powder is, from the point of view of the increase of yield stress of mortar caused by stone powder, the plastic viscosity of limestone sand slurry has a good correlation with the specific surface area of aggregate. The plastic viscosity of mechanical sand slurry increases with the increase of stone powder content.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU578.1

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