高强混凝土高性能化应用基础研究

发布时间：2018-09-07 07:28

【摘要】：随着我国社会和经济的快速发展,高速铁路建设规模逐渐增加,高强混凝土在铁路中的应用越来越广、用量越来越大。虽然高速铁路无砟轨道具有平顺性好、变形小、可靠度高和日常维修少等优点,然而,高速铁路预制构件用高强混凝土存在粘度高、脆性大等问题。为保证结构安全服役,必须解决高强混凝土存在的问题,主要进行了以下四方面的研究。首先,研究了等强度的不同胶凝材料用量混凝土的弯曲韧性和冲击韧性。结果表明,降低胶凝材料用量可以明显提高混凝土的冲击韧性和弯曲韧性。并采用热分析仪、压汞仪和莱卡显微镜等研究分析了低胶凝材料用量混凝土的增韧机理,胶凝材料用量的降低导致混凝土中缺陷含量降低,同时骨料体积分数的增加更好的起到“阻裂”和“耗能”的作用,共同导致混凝土弯曲韧性和冲击韧性提高。确定了降低胶凝材料用量是提高混凝土韧性的有效手段,为提出低胶凝材料用量混凝土制备技术奠定了理论基础。其次,在研究混凝土砂率、水胶比、包裹骨料浆体厚度和胶凝材料组成的基础上提出了低胶凝材料用量混凝土的制备方法。①建立骨料堆积模型,通过砂石骨料的最大堆积密实度确定砂率为38%,并计算骨料的堆积密实度为84%；②根据混凝土流变性能确定水胶比宜为0.35；③根据工作性能选取包裹骨料浆体膜厚度,计算浆体用量；④采用绝对体积法计算胶凝材料、水和砂石用量；⑤根据混凝土强度等级确定混凝土胶凝材料组成。并采用提高胶凝材料活性的方法制备出了低胶凝材料用量的高强混凝土。当胶凝材料用量为370 kg/m3、组成为90% P·W62.5白水泥和10%S95矿渣粉、用水量为130 kg/m3时,混凝土强度等级可达C80。再次,在制备出不同强度等级低胶凝材料用量混凝土的基础上,研究了低胶凝材料用量混凝土的工作性能评价方法,并对比了等强度的低胶凝材料用量混凝土与工程常用混凝土的热物理性能、体积稳定性能和抗裂性能。结果表明,低胶凝材料用量混凝土应根据坍落度选择工作性能评价方法；降低胶凝材料用量可以明显降低绝热温升、提高体积稳定性和抗裂性。最后,以低胶凝材料用量混凝土理论作指导进行了工程应用研究。结果表明,采用低胶凝材料用量混凝土制备轨道板和轨枕可以提高工作效率,制备出的预制构件表面光滑密实,裂缝及缺损数量显著降低。
[Abstract]:With the rapid development of our society and economy, the construction scale of high-speed railway is increasing gradually, and the application of high-strength concrete in railway is more and more extensive. Although ballastless track of high-speed railway has the advantages of good smoothness, small deformation, high reliability and less daily maintenance, the problems of high strength concrete for high speed railway prefabricated components are high viscosity and brittleness. In order to ensure the safe service of the structure, it is necessary to solve the existing problems of high strength concrete. First, the flexural toughness and impact toughness of concrete with equal strength and different content of cementing materials are studied. The results show that the impact toughness and flexural toughness of concrete can be improved obviously by reducing the amount of cementitious material. The toughening mechanism of concrete with low cementitious content is analyzed by means of thermal analyzer, mercury injection instrument and Leica microscope. The decrease of cement content leads to the decrease of defect content in concrete. At the same time, the increase of aggregate volume fraction plays a better role of "crack resistance" and "energy consumption", which leads to the improvement of flexural toughness and impact toughness of concrete. It is determined that reducing the amount of cementitious material is an effective means to improve the toughness of concrete, which lays a theoretical foundation for the preparation technology of concrete with low content of cementitious material. Secondly, on the basis of studying the sand ratio of concrete, the ratio of water to binder, the thickness of aggregate paste and the composition of cementing material, the preparation method of concrete with low content of cementitious material is put forward. According to the maximum compactness of aggregate, the sand ratio is determined to be 38, and the compactness of aggregate is calculated to be 84 / 2. According to the rheological properties of concrete, the ratio of water to binder is determined to be 0.35 and the thickness of coated aggregate membrane is selected according to the working performance. The cement material is calculated by absolute volume method, and the composition of concrete cementitious material is determined according to the strength grade of concrete by the amount of water and sand. High strength concrete with low content of cementitious material was prepared by improving the activity of cementitious material. When the amount of cementitious material is 370 kg/m3, and the composition of cement is 90% P W 62.5 white cement and 10%S95 slag powder, and the water consumption is 130 kg/m3, the strength grade of concrete can reach C80. Thirdly, on the basis of preparing concrete with different strength grade and low cementing material dosage, the evaluation method of working performance of low cementitious material concrete is studied. The thermo-physical properties, volume stability and crack resistance of concrete with equal strength and low cementitious content are compared with those of common concrete. The results show that the evaluation method of working performance should be selected according to the slump of concrete with low cement content, and the adiabatic temperature rise can be obviously reduced and the volume stability and crack resistance can be improved by reducing the amount of cement material. Finally, the engineering application is studied under the guidance of the theory of low cement content concrete. The results show that the working efficiency of track slab and sleeper can be improved by using low cementitious material content concrete, the surface of the prefabricated member is smooth and dense, and the number of cracks and defects is significantly reduced.
【学位授予单位】：中国铁道科学研究院
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU528

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