大流动度混凝土路面早期开裂机理研究
发布时间：2018-12-27 09:01
【摘要】：大流动度混凝土指拌合物坍落度值在160mm以上的混凝土,它是混凝土研究发展的一个新方向。近年来随着外加剂和矿物掺合料应用研究的发展,大流动度混凝土在国内外的研究取得了很大进展。将大流动度混凝土用于路面工程,可以减轻铺筑混凝土的劳动强度和工作量、节省能源、减少噪声、保护环境、提高施工进度、增加路面板内混凝土的均质性。但它的流动性也产生了一些负面作用,如早期收缩开裂现象比较严重,导致大流动度混凝土路面实际使用年限达不到设计年限的要求。因此,研究大流动度混凝土路面的早期开裂机理非常重要。本文首先初步探讨了大流动度混凝土路面的裂缝成因及控制措施,然后通过正交试验,以坍落度、7d、28d抗折、抗压强度为评价指标,进行配合比设计,优选大流动度路面混凝土配合比设计参数,试验表明水胶比是影响大流动度混凝土工作性与抗折强度的关键因素。再根据所得的配合比以水胶比、砂率以及粉煤灰掺量为影响因素进行了混凝土的早期开裂试验,试验数据表明随着粉煤灰掺量的增加,大流动度混凝土单位面积的总开裂面积先减小后增加,在混凝土中掺入一定量粉煤灰能有效减少开裂,随着砂率的增加,大流动度混凝土的早期开裂逐渐增加,随着水胶比的增加,大流动度混凝土的早期开裂急剧增加。然后针对引起混凝土早期开裂的本质因素即混凝土内部的温度梯度和湿度梯度,系统地分析了混凝土温度场与湿度场的变化规律及温度应力和干缩应力的数值计算方法。最后通过有限元分析软件MIDAS对大流动度混凝土路面板的温度应力与干缩应力进行数值计算,分析其对混凝土早期开裂的影响规律,并将计算所得的温度应力与干缩应力叠加后对大流动度混凝土路面的早期开裂进行风险判断。
[Abstract]:Large fluidity concrete refers to concrete whose slump value is above 160mm, which is a new direction in the research and development of concrete. In recent years, with the development of admixture and mineral admixture, great progress has been made in the research of high fluidity concrete at home and abroad. Using large fluidity concrete in pavement engineering can reduce the labor intensity and workload of paving concrete, save energy, reduce noise, protect environment, improve construction progress and increase the homogeneity of concrete in pavement slab. However, its fluidity also has some negative effects, such as serious early shrinkage and cracking phenomenon, which leads to the fact that the actual service life of high flow concrete pavement is not up to the requirement of design life. Therefore, it is very important to study the early cracking mechanism of high flow concrete pavement. In this paper, the causes and control measures of cracks in high flow concrete pavement are discussed, and then through orthogonal test, the mix ratio is designed with slump, 7d ~ 28d bending resistance and compressive strength as evaluation index. The optimum design parameters of concrete mixture ratio for high fluidity pavement are selected. The test results show that the water-binder ratio is the key factor affecting the workability and flexural strength of high flow concrete. According to the mixture ratio of water and binder, sand ratio and the content of fly ash as the influencing factors, the early cracking test of concrete is carried out. The experimental data show that with the increase of the content of fly ash, The total cracking area of high fluidity concrete decreases first and then increases. Adding a certain amount of fly ash into concrete can effectively reduce the cracking. With the increase of sand ratio, the early cracking of high flow concrete increases gradually. With the increase of water / binder ratio, the early cracking of high fluidity concrete increases sharply. Then the variation law of temperature field and humidity field of concrete and the numerical calculation method of temperature stress and dry shrinkage stress are analyzed systematically in view of the essential factors that cause the early cracking of concrete namely the temperature gradient and humidity gradient inside the concrete. Finally, the temperature stress and dry shrinkage stress of high flow concrete pavement slab are numerically calculated by finite element analysis software MIDAS, and its influence on early cracking of concrete is analyzed. The calculated temperature stress and dry shrinkage stress are superimposed to judge the risk of early cracking of high flow concrete pavement.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.216;U418.6
本文编号：2392822
[Abstract]:Large fluidity concrete refers to concrete whose slump value is above 160mm, which is a new direction in the research and development of concrete. In recent years, with the development of admixture and mineral admixture, great progress has been made in the research of high fluidity concrete at home and abroad. Using large fluidity concrete in pavement engineering can reduce the labor intensity and workload of paving concrete, save energy, reduce noise, protect environment, improve construction progress and increase the homogeneity of concrete in pavement slab. However, its fluidity also has some negative effects, such as serious early shrinkage and cracking phenomenon, which leads to the fact that the actual service life of high flow concrete pavement is not up to the requirement of design life. Therefore, it is very important to study the early cracking mechanism of high flow concrete pavement. In this paper, the causes and control measures of cracks in high flow concrete pavement are discussed, and then through orthogonal test, the mix ratio is designed with slump, 7d ~ 28d bending resistance and compressive strength as evaluation index. The optimum design parameters of concrete mixture ratio for high fluidity pavement are selected. The test results show that the water-binder ratio is the key factor affecting the workability and flexural strength of high flow concrete. According to the mixture ratio of water and binder, sand ratio and the content of fly ash as the influencing factors, the early cracking test of concrete is carried out. The experimental data show that with the increase of the content of fly ash, The total cracking area of high fluidity concrete decreases first and then increases. Adding a certain amount of fly ash into concrete can effectively reduce the cracking. With the increase of sand ratio, the early cracking of high flow concrete increases gradually. With the increase of water / binder ratio, the early cracking of high fluidity concrete increases sharply. Then the variation law of temperature field and humidity field of concrete and the numerical calculation method of temperature stress and dry shrinkage stress are analyzed systematically in view of the essential factors that cause the early cracking of concrete namely the temperature gradient and humidity gradient inside the concrete. Finally, the temperature stress and dry shrinkage stress of high flow concrete pavement slab are numerically calculated by finite element analysis software MIDAS, and its influence on early cracking of concrete is analyzed. The calculated temperature stress and dry shrinkage stress are superimposed to judge the risk of early cracking of high flow concrete pavement.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.216;U418.6
【参考文献】
相关期刊论文 前2条
1 万在龙,袁勇,章勇武;基于孔结构模型的混凝土干缩变形理论分析[J];华中科技大学学报;2001年10期
2 马跃先;陈晓光;;水工混凝土的湿度场及干缩应力研究[J];水力发电学报;2008年03期
相关硕士学位论文 前1条
1 郑翥鹏;高强与高性能混凝土的抗裂影响因素及理论分析[D];福州大学;2003年
，本文编号：2392822
本文链接：https://www.wllwen.com/kejilunwen/daoluqiaoliang/2392822.html
