持续荷作用下粉煤灰混凝土力学性能发展研究

发布时间：2018-04-04 20:36

本文选题：持续荷载　切入点：粉煤灰混凝土　出处：《北京交通大学》2017年硕士论文

【摘要】：实际结构中的混凝土均处于受力状态下,结构受载的龄期不断提前,加载时混凝土强度可能仍未发展成熟,将在荷载下继续发展,同时,荷载下混凝土力学性能发展将与无荷载状态下有所不同。大量试验数据表明,低应力下混凝土力学性能有增强作用,而目前对混凝土力学性能的研究几乎没有考虑荷载对混凝土性能的作用,故需要对荷载下粉煤灰混凝土力学性能进行研究。随着工程技术不断进步,混凝土的配合比也越来越复杂,新的掺合料和添加剂的加入使混凝土性能有很大的变化,例如粉煤灰。粉煤灰的掺入使混凝土内部水化机理发生了变化,也使混凝土后期力学性能与普通混凝土有很大区别,在荷载作用下这一问题变得更加复杂。本文研究了荷载作用下粉煤灰混凝土力学性能发展,主要工作如下:1.对粉煤灰混凝土荷载作用下的抗压强度、弹性模量随龄期的发展进行了试验研究,试验设计了 40%、60%两种中高掺量的粉煤灰混凝土,自制了三角形试验加载设备,对加载试件在第28天施加,荷载等级为未加载试件28天棱柱体抗压强度的20%,在指定龄期测试加载与非加载试件抗压强度与弹性模量;2.分析了应力下粉煤灰混凝土力学性能增强的机理,考虑应力下额外的水泥水化、火山灰反应以及额外反应下骨料密度的改变,在浆体、浆体-骨料两个尺度上建立适用粉煤灰混凝土的代表体积单元(REV),通过缩核水化模型得到水化及粉煤灰反应程度发展情况,得出RVE内各相材料体积分数;3.考虑骨料体积分数及类型,建立了荷载作用下粉煤灰混凝土抗压强度发展模型,分析加载时间和荷载等级对荷载下粉煤灰混凝土抗压强度发展的影响;4.在细观力学框架下,依次计算两代表体积单元有效刚度,建立了荷载作用下粉煤灰混凝土弹性模量发展模型,分析加载时间和荷载等级对荷载下粉煤灰混凝土弹性模量发展的影响。
[Abstract]:The concrete in the actual structure is in the state of stress, and the age of the structural load is advancing continuously. The strength of the concrete under loading may not be mature, and it will continue to develop under the load, at the same time,The development of mechanical properties of concrete under load will be different from that under load.A large number of experimental data show that the mechanical properties of concrete can be enhanced under low stress, but the present research on the mechanical properties of concrete hardly considers the effect of load on the performance of concrete.Therefore, it is necessary to study the mechanical properties of fly ash concrete under load.With the development of engineering technology, the mix ratio of concrete is becoming more and more complicated. The addition of new admixtures and additives has greatly changed the performance of concrete, such as fly ash.The hydration mechanism of concrete is changed by the addition of fly ash, and the mechanical properties of concrete in the later stage are different from that of ordinary concrete, and the problem becomes more complicated under the action of load.The development of mechanical properties of fly ash concrete under load is studied in this paper. The main work is as follows: 1.The compressive strength and elastic modulus of fly ash concrete under loading are studied experimentally with the development of age. Two kinds of fly ash concrete with 40% and 60% content of fly ash concrete with high content are designed, and the triangular test loading equipment is made.On the 28th day, the loading grade is 20 days of the prismatic compressive strength of the unloaded specimens, and the compressive strength and elastic modulus of the loaded and unloaded specimens are 2.The mechanism of strengthening mechanical properties of fly ash concrete under stress is analyzed. Considering the additional cement hydration under stress, the pozzolanic reaction and the change of aggregate density under extra reaction,The representative volume unit of fly ash concrete was established on the two scales of slurry and aggregate. The hydration and reaction degree of fly ash were obtained by the hydration model of shrinkage nucleus, and the volume fraction of each phase material in RVE was obtained.Considering the volume fraction and type of aggregate, the development model of compressive strength of fly ash concrete under load is established, and the influence of loading time and load grade on the development of compressive strength of fly ash concrete under load is analyzed.Under the meso-mechanical framework, the effective stiffness of two volumetric elements is calculated in turn, and the elastic modulus development model of fly ash concrete under load is established.The influence of loading time and load grade on elastic modulus development of fly ash concrete under load is analyzed.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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