LC50轻骨料混凝土配合比设计及性能研究

发布时间：2018-12-20 07:16

【摘要】：随着现代建筑向着高层、大跨径方向的发展，人们对混凝土的要求也越来越高，普通高强混凝土因其自重大问题的存在，，在大型工程使用中受到越来越多的约束。而近年来人造轻骨料特别是高强陶粒的快速发展为解决这个问题提供了一个契机。高强陶粒具有轻质、高强、低吸水率的特点，将其用于混凝土的制备能在保证相同强度等级的情况下降低自重20%～30%。为此本文针对LC50轻骨料混凝土的配合比设计及各方面性能展开了系统研究，获得以下结论：（1）选用湖北宜昌宝珠陶粒有限公司生产的高强页岩陶粒作为粗骨料，通过配合比设计确定了一组初始配合比，并通过试验研究了水灰比、砂率与骨料平均粒径对LC50轻骨料混凝土坍落度、表观密度以及强度等性能的影响规律，对初始配合比进行优选，成功配制出强度等级为LC50的轻骨料混凝土。（2）在配制出LC50轻骨料混凝土的基础上研究了预湿时间、颗粒类型、粒径、粉煤灰、砂的细度模数、细骨料类型等对拌合物性能的影响规律，通过试验研究，确定了对LC50轻骨料混凝土拌合物性能影响的主要因素，为配制具有良好工作性能LC50轻骨料混凝土提供了一定的理论基础与技术支持。（3）对LC50轻骨料混凝土力学性能与耐久性能进行了研究，试验结果表明，粉煤灰的掺入能够提升LC50轻骨料混凝土的后期强度，而预湿处理会降低混凝土早期强度，但是有益于后期强度的发展；粉煤灰和钢渣粉的掺入降低了轻骨料混凝土的抗碳化性能；而超细粉煤灰和磨细矿粉的掺入，却能在一定程度上提升LC50轻骨料混凝土抗碳化性能；LC50轻骨料混凝土在碳化作用下干缩变形会显著增长，但利用矿物掺合料等量取代水泥掺入，能较好的抑制其碳化收缩率；同时良好的预湿工艺对也轻骨料混凝土的减缩防裂是较为有利的。（4）对LC50轻骨料混凝土在荷载条件下与硫酸盐侵蚀的非荷载条件下的内部微观裂纹扩展规律进行了研究，引入工业计算机断层扫描系统检测了不同类型LC50轻骨料混凝土的内部裂纹状况，以此分析了轻骨料混凝土的损坏机理，发现了LC50轻骨料混凝土破坏过程中裂纹扩展规律与普通混凝土的诸多不同，为解释LC50轻骨料混凝土实际应用过程的损害机制提供了理论依据。
[Abstract]:With the development of modern building towards high-rise and long-span direction, the demand for concrete is becoming higher and higher. Because of its serious problems, ordinary high-strength concrete is subjected to more and more constraints in the use of large-scale projects. In recent years, the rapid development of artificial lightweight aggregate, especially high-strength ceramsite, provides an opportunity to solve this problem. High strength ceramsite has the characteristics of light weight, high strength and low water absorption. Its application in the preparation of concrete can reduce the weight of 20% and 30% under the condition of the same strength grade. In this paper, the proportion design and performance of LC50 lightweight aggregate concrete are systematically studied, and the following conclusions are obtained: (1) the high strength shale ceramsite produced by Yichang Baozhu Ceramsite Co., Ltd., Hubei Province, is selected as coarse aggregate. A group of initial mix ratios were determined by mix ratio design, and the effects of water-cement ratio, sand ratio and average particle size of aggregate on slump, apparent density and strength of LC50 lightweight aggregate concrete were studied. The lightweight aggregate concrete with LC50 strength grade was successfully prepared by selecting the initial mix ratio. (2) based on the preparation of LC50 lightweight aggregate concrete, the effects of pre-wetting time, particle type, particle size, fly ash, fineness modulus of sand and fine aggregate type on the properties of the mixture were studied. The main factors affecting the physical properties of LC50 lightweight aggregate concrete are determined, which provide a theoretical basis and technical support for the preparation of LC50 lightweight aggregate concrete with good working performance. (3) the mechanical properties and durability of LC50 lightweight aggregate concrete are studied. The experimental results show that the addition of fly ash can enhance the later strength of LC50 lightweight aggregate concrete, while pre-wetting treatment can reduce the early strength of concrete. But it is beneficial to the development of the later intensity; The addition of fly ash and steel slag powder reduces the carbonation resistance of lightweight aggregate concrete, while the addition of ultrafine fly ash and fine grinding powder can improve the carbonation resistance of LC50 lightweight aggregate concrete to some extent. The dry shrinkage deformation of LC50 lightweight aggregate concrete will increase significantly under carbonization, but the carbonation shrinkage of LC50 lightweight aggregate concrete can be inhibited by using mineral admixture to replace cement in the same amount. At the same time, a good pre-wetting process is beneficial to reduce shrinkage and crack of lightweight aggregate concrete. (4) the microcosmic crack propagation law of LC50 lightweight aggregate concrete under load and sulfate erosion is studied. The internal cracks of different types of LC50 lightweight aggregate concrete were detected by using the industrial computer tomography system, and the damage mechanism of the lightweight aggregate concrete was analyzed. It is found that the crack propagation law of LC50 lightweight aggregate concrete is different from that of ordinary concrete, which provides a theoretical basis for explaining the damage mechanism of LC50 lightweight aggregate concrete in practical application.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.2

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