高强轻骨料混凝土收缩开裂试验研究

发布时间：2018-07-28 21:25

【摘要】：根据规定,轻骨料混凝土是指(Lightweight Aggregate Concrete,简称为LWC)利用轻粗骨料、轻砂(或普通砂)、水泥和水配制而成,干表观密度低于1950kg/m3的混凝土。轻骨料混凝土因为使用陶粒等作为粗骨料,其混凝土的密度比传统普通混凝土的密度低20%~30%。对于需要大量混凝土的建筑来说,采用低密度、强度高的轻骨料混凝土,会带来经济和施工技术方面非常大的优势。但是对于轻骨料混凝土来说,相对于普通混凝土,后期收缩量大是轻骨料混凝土的一个极大的劣势,这也是导致轻骨料混凝土未大量普及利用的原因之一。在自由状态下,混凝土制成品的自由收缩不会对其本身产生有害的影响。在自由状态下,任何物体的收缩均不会对物体本身产生副作用。但混凝土在结构中应用时,由混凝土浇筑成的结构构件由于处于超静定状态之下,当自身发生收缩变形时,收缩会产生收缩应力,而在约束条件下收缩应力不能释放,当收缩应力的大小大于混凝土自身的抗拉强度时,就会产生裂缝,最终影响整个结构的耐久性能。本文利用云南宝珠页岩陶粒配制出陶粒混凝土,针对试验中的轻骨料混凝土主要展开了以下试验研究:(1)本文以实验目的要求配置出高强LC60轻骨料混凝土,并对高强LC60陶粒混凝土在自由状态下的自由收缩进行试验研究。试验对八种不同配合比的试块进行了自由收缩试验。仔细研究了不同膨胀剂掺量以及不同聚丙烯掺量下的LC60轻骨料混凝土的收缩状况。结果表明:膨胀剂对轻骨料混凝土又很显著的抗收缩性能,并且三个掺量中,综合力学指标以及限制收缩的作用,试验得出结论在轻骨料混凝土中掺加8%时,既能满足混凝土试件的力学性能,并且收缩量也很理想;而对于掺加聚丙烯纤维,发现掺加有聚丙烯纤维的混凝土试块也会减小其收缩。试验中进行了双掺聚丙烯纤维和膨胀剂配合比的试验,结果显示双掺组合的物理性能基本上没有降低,并且对于减小轻骨料混凝土的收缩量具有很好的作用。(2)开裂是影响混凝土耐久性能的关键因素之一,轻集料混凝土的收缩量大无疑更加剧了开裂。文章中利用朱涵教授课题组多次改进之后的外方内圆试验模具对轻集料混凝土约束状态下的开裂进行了研究。在混凝土中掺入聚丙烯纤维与膨胀剂均能缓解混凝土裂缝的产生,但是这两种物质阻止混凝土裂缝的产生却是从两个机理方向发挥作用的。本文着重研究了在不同掺量下的聚丙烯纤维和膨胀剂如何影响轻骨料的开裂。并且本实验还加入了传统C60混凝土,并对轻集料混凝土与传统C60混凝土进行了比较研究。对五种配合比总共八个外方内圆试验试件进行了试验,并采用应变仪进行了数据采集。结果表明:掺加膨胀剂以及聚丙烯都会提高混凝土的抗开裂能力,掺加0.9kg/m3的聚丙烯纤维以及8%掺量的膨胀剂对高强轻骨料混凝土的抗开裂性能有很大的提高。(3)试验对掺加膨胀剂与聚丙烯纤维对LC60混凝土的基本力学性能做了研究,研究了外掺假物对立方体抗压强度、劈裂抗拉强度、抗折强度以及弹性模量的影响。
[Abstract]:According to the regulations, light aggregate concrete is a concrete (Lightweight Aggregate Concrete, referred to as LWC) using light coarse aggregate, light sand (or ordinary sand), cement and water, and the density of dry surface is lower than 1950kg/m3. The density of lightweight aggregate concrete is compared with the density of traditional concrete because of the use of ceramsite as coarse aggregate. Low 20%~30%. for a large number of concrete buildings, the use of low density, high strength lightweight aggregate concrete will bring a great advantage in economic and construction technology. But for lightweight aggregate concrete, relative to the ordinary concrete, the later shrinkage is a great disadvantage of the lightweight aggregate concrete, which is also a result. One of the reasons that the lightweight aggregate concrete is not widely used. In free state, the free shrinkage of the finished product will not have a harmful effect on it itself. In free state, the shrinkage of any object will not have side effects on the object itself. But when the concrete is used in the structure, the structure of the concrete is made of concrete. Under the condition of statically indeterminate state, shrinkage stress is produced when the contraction deformation occurs, and the shrinkage stress can not be released under the constraint conditions. When the shrinkage stress is larger than the tensile strength of concrete itself, it will produce cracks and ultimately affect the durability of the whole structure. This paper uses the Yunnan treasure shale ceramsite. The ceramsite concrete was prepared, and the following experimental research was carried out in light of the light aggregate concrete in the experiment. (1) the high strength LC60 lightweight aggregate concrete was configured in this paper, and the free shrinkage of high strength LC60 ceramsite concrete under free condition was tested. The test was carried out on the test blocks of eight different mix ratios. According to the shrinkage test, the shrinkage of LC60 light aggregate concrete with different expansive agents and different polypropylene content was carefully studied. The results showed that the expansive agent had significant anti shrinkage performance to light aggregate concrete, and in the three admixtures, the comprehensive mechanical index and the effect of limiting shrinkage were found, and the conclusion was concluded in the light aggregate concrete mixture. When adding 8% in the soil, it can not only satisfy the mechanical properties of the concrete specimen, but also the shrinkage is ideal. For the addition of polypropylene fiber, it is found that the shrinkage of concrete mixed with polypropylene fiber can also be reduced. The test of the mixing ratio of polypropylene fiber and expansion agent is carried out in the experiment, and the results show the physical properties of the double mixing. It can basically not be reduced, and it has a good effect on reducing the shrinkage of lightweight aggregate concrete. (2) cracking is one of the key factors affecting the durability of concrete. The shrinkage of lightweight aggregate concrete is undoubtedly more cracking. The cracking of lightweight aggregate concrete under constraint condition is studied. The addition of polypropylene fiber and expansive agent in concrete can alleviate the formation of concrete cracks, but these two substances play a role in preventing the production of concrete cracks from two mechanism directions. How does the expander affect the cracking of light aggregate, and the traditional C60 concrete is added in this experiment, and the comparison of the light aggregate concrete and the traditional C60 concrete is carried out. The test of the five combinations of eight outer inner circle test specimens is carried out and the data collection is carried out by the strain gauge. The results show that the expansion agent is added and the expansion agent is added as well. Polypropylene can improve the anti cracking ability of concrete. The anti cracking performance of high strength lightweight aggregate concrete is greatly improved by adding 0.9kg/m3 polypropylene fiber and 8% content of expansive agent. (3) the basic mechanical properties of LC60 concrete are studied by adding expansive agent and polypropylene fiber, and the cube is studied on the cube. The influence of compressive strength, splitting tensile strength, flexural strength and modulus of elasticity.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528

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