混凝土工作性控制技术及评估方法研究

发布时间：2018-05-01 11:28

本文选题：混凝土 + 工作性　；参考：《东南大学》2015年硕士论文

【摘要】：良好工作性的新拌混凝土对保障硬化后性能十分重要,建立合理、有效的工作性评估方法有益于保证工程质量。本文以坍落度140mm到220mm的C50大流动性混凝土为例,研究了工作性的差异对力学性能、耐久性能匀质性的影响,在此基础上评估混凝土的工作性；并尝试将图像处理方法引入到工作性评估中。同时研究了不同因素对浆体流动性、粘聚性、保水性的影响规律,从而达到有效控制混凝土工作性的目的。研究了水胶比、矿物掺合料、减水剂对水泥净浆、砂浆流动性、粘聚性、保水性的影响规律。试验结果表明：水胶比、矿粉、减水剂掺量的增加对浆体流动性的改善效果较为明显,但会带来粘聚性、保水性的变差,大掺量矿粉的使用会降低浆体粘聚性、保水性；而Ⅰ级粉煤灰在增大流动性的同时能够保持很好的粘聚性、保水性,能够弥补因增大减水剂和矿粉掺量带来的工作性负面影响。砂浆和水泥净浆在不同因素影响下工作性发展规律相近,尤其是二者粘聚性相关性较大,表明通过浆体粘聚性影响因素控制混凝土上作性的可行性并在工程中得到了应用。阐明了工作性与硬化混凝土力学性能、耐久性能的匀质性关系。随着混凝土工作性的变差,不同部位混凝土的抗压强度、动弹性模量、氯离子迁移系数、气体渗透系数、干缩变形的离差也越来越大,即混凝土的匀质性越差。骨料离析率、泌水率等工作性指标与混凝土匀质性存在关联,并以此建立了基于混凝土匀质性的工作性评估方法,为现场工作性的量化评估提供依据。探索了图像处理方法在浆体工作性评估中的应用。通过图像分析获取了浆体扩展面积随时间实时变化曲线并以计算扩展度的形式来表现,极大地提高了流动性测量的精度,并通过浆体流动截止时间很好地表征了浆体的粘聚性,同时获取了浆体表面气泡实时变化规律以及最终扩展形态。为现场混凝土工作性的快速评估提供了理论支撑和可行性验证。通过微观分析手段,检测不同工作性混凝土在孔结构、水化产物、微观形貌的差异,结果证实匀质性的差异在微观尺度上也得到了反映。
[Abstract]:The good workability of fresh concrete is very important to guarantee the performance after hardening. Establishing a reasonable and effective evaluation method of workability is beneficial to guarantee the engineering quality. Taking C50 fluidity concrete with slump 140mm to 220mm as an example, the influence of workability difference on mechanical properties and durability homogeneity is studied, and the workability of concrete is evaluated. And try to introduce the image processing method into the evaluation of workability. At the same time, the effects of different factors on slurry fluidity, agglomeration and water retention are studied, so as to effectively control the workability of concrete. The effects of water / binder ratio, mineral admixture and water reducing agent on cement paste, mortar fluidity, agglomeration and water retention were studied. The results show that: the increase of water / binder ratio, ore powder and water reducing agent content can improve the slurry fluidity obviously, but it will bring about the agglomeration, the water retention property becomes worse, and the use of the large amount of mineral powder will reduce the slurry agglomeration and water retention; The first grade fly ash can keep good cohesion and water retention while increasing the fluidity, which can make up for the negative effect of increasing the amount of water reducer and mineral powder. The development law of workability of mortar and cement mortar is similar under the influence of different factors, especially the relativity of their cohesion, which indicates that it is feasible to control the performance of concrete by influencing factors of mortar cohesion and has been applied in engineering. The homogeneity relationship between workability and mechanical properties and durability of hardened concrete is expounded. As the workability of concrete becomes worse, the difference of compressive strength, dynamic elastic modulus, chloride ion transfer coefficient, gas permeability coefficient and dry shrinkage deformation of concrete is increasing, that is to say, the homogeneity of concrete is worse. The workability indexes such as aggregate segregation rate, bleeding rate and so on are related to the homogeneity of concrete. Based on this, a workability evaluation method based on concrete homogeneity is established, which provides the basis for the quantitative evaluation of on-site workability. The application of image processing in the evaluation of slurry workability is explored. The real time curve of slurry expansion area is obtained by image analysis and expressed in the form of calculating expansion degree, which greatly improves the accuracy of flow measurement, and indicates the cohesiveness of slurry through the cut-off time of slurry flow. At the same time, the real-time change rule and the final expansion morphology of the bubbles on the slurry surface were obtained. It provides theoretical support and feasibility verification for quick evaluation of site concrete workability. The difference of pore structure, hydration product and microstructure of different working concrete was detected by means of microscopic analysis. The results show that the difference of homogeneity is also reflected in microscopic scale.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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