基于温度应力试验机（TSTM）的大坝混凝土抗裂性能实验研究

发布时间：2018-06-12 19:34

本文选题：大坝混凝土 + 传统抗裂性能指标　；参考：《浙江工业大学》2014年硕士论文

【摘要】：大坝混凝土的抗裂性能一直是工程界十分关注的问题。避免产生和减少裂缝一直是大坝混凝土的重点和难点,因此抗裂性能评价方法和评价指标显得尤为重要。当前我国在涉及温度应力的抗裂性能研究中大多采用水泥水化热、混凝土绝热温升、收缩变形测量等较为单一或圆环约束、平板约束等试件尺寸较小的方法,没有综合温度履历与约束程度条件的影响来评价混凝土的早期开裂,与混凝土的工程实际相差较大。因此需要探索出评价混凝土抗裂性能的新方法,可以为工程技术人员在选用混凝土材料时提供有用的信息,以有效地保证大坝在各种环境条件下满足既定的服役要求。本文以三种不同种类水泥(即中热硅酸盐水泥MH,普通低热硅酸盐水泥LHA和高含氧化镁低热硅酸盐水泥LHB)为对象,通过对试验室标准养护条件下试件的相关力学性能指标的测定,得到极限拉伸值,拉压比和弹强比这三个抗裂性能传统评价指标,以此评价混凝土配合比之间的抗裂性能优劣关系。并且根据评价结果对三大传统评价指标的吻合性进行分析判断。在此基础上,利用温度应力试验机(TSTM),对混凝土试件进行单轴约束试验,得到混凝土在不同温度历程下的实时参数以及抗裂性能指标。根据TSTM试验的相关评价体系对混凝土各配合比进行抗裂性能评价。最后通过试验结果将传统抗裂性能评价方法和基于TSTM的抗裂性能评价方法进行对比和优劣分析。研究结果表明：1、在两种不同的评价体系中,0.4水胶比的抗裂性能都优于0.5水胶比,氧化镁的微膨胀性质表现出对混凝土抗裂性能的有利影响2、在TSTM温度履历不同的情况下,三种胶凝材料(MH,LHA)和LHB)的抗裂性能优劣顺序会发生相应变动,3、通过徐变分析,三种胶凝材料在温升阶段后的膨胀更有利与混凝土的抗裂性能。4、综合两种试验方法和两套抗裂性能评价指标,结果表明传统抗裂性能评价方法并不能很好地体现出不同胶凝材料对抗裂性能的影响,也不能反映低热水泥、微膨胀水泥在控制大坝混凝土早期裂缝方面的潜在优势,并且三种传统评价指标存在评价结果不一致的情况,用单一指标来判断某种大坝混凝土的抗裂性能的可信度不高。而利用加权统计,在相同条件下,将TSTM抗裂性能评价结果与综合加权后的传统抗裂性能评价结果进行对比分析,结果表明两者具有较好的相似度。但在评价指标细节方面,TSTM包含了力学,变形和热学三方面的评价信息,从而使评价结果更为合理和全面。
[Abstract]:The crack resistance performance of the dam concrete has always been a very concern in the engineering field. Avoiding and reducing the cracks is always the key and difficult point of the concrete of the dam. Therefore, the evaluation method and the evaluation index of the crack resistance are particularly important. In the current research on the cracking resistance of the thermal stress in China, the cement hydration heat is mostly used. Adiabatic temperature rise, measurement of shrinkage deformation and so on are relatively single or ring constraint. The method of smaller size of plate constraints, such as flat plate constraints, does not evaluate the early cracking of concrete with the influence of comprehensive temperature and constraint conditions, which is quite different from the concrete engineering practice. Therefore, a new method for evaluating the crack resistance of concrete is needed. It is believed that engineers and technicians will provide useful information when selecting concrete materials to effectively ensure that the dam meets the established service requirements under various environmental conditions.
In this paper, three different kinds of cement (medium heat Portland cement MH, ordinary low hot Portland cement LHA and high Magnesium Oxide low heat Portland cement LHB) are taken as the object. By measuring the related mechanical properties of the test specimen under the standard curing condition of the test room, the limit tensile value, the tensile pressure ratio and the elastic strength ratio are obtained by the traditional evaluation. In order to evaluate the relationship between the anti cracking performance of the concrete mix ratio, and to analyze the anastomosis of the three traditional evaluation indexes according to the evaluation results, the temperature stress test machine (TSTM) is used to test the concrete specimens by single axis constraint on this basis, and the concrete in real time under different temperature processes is obtained. Parameters and anti cracking performance indexes. According to the relevant evaluation system of TSTM test, the anti cracking performance of concrete mixture ratio is evaluated. Finally, the traditional anti cracking performance evaluation method and the TSTM based anti cracking performance evaluation method are compared and analyzed.
The results show that: 1, in the two different evaluation systems, the cracking resistance of 0.4 water to glue ratio is superior to 0.5 water glue ratio, and the micro expansion property of Magnesium Oxide shows a favorable effect on the crack resistance of concrete 2. Under the different temperature of TSTM, the order of anti cracking performance of three kinds of cementitious materials (MH, LHA) and LHB will change correspondingly. 3, 3, through the creep analysis, the expansion of three kinds of cementitious materials after the temperature rise stage is more favorable to the cracking resistance of concrete.4, comprehensive two test methods and two sets of anti cracking performance evaluation indexes. The results show that the traditional anti cracking performance evaluation method can not reflect the effect of different cementitious materials on the cracking resistance and can not reflect the low resistance. The potential advantage of hot cement and micro expansive cement in controlling the early cracks in concrete of dam concrete, and the three traditional evaluation indexes are not consistent in the evaluation results. The reliability of the crack resistance of a certain dam concrete is not high with a single index. And the TSTM cracking performance evaluation is based on the same conditions. The results of the traditional anti cracking performance evaluation after the comprehensive weighting are compared and analyzed. The results show that they have good similarity. But in the detail of the evaluation index, TSTM contains three aspects of the evaluation information of mechanics, deformation and heat, so that the evaluation results are more reasonable and complete.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV431

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