纤维混凝土界面性能及纤维作用机理研究

【作者】 张红州；

【导师】 刘锋；

【作者基本信息】 广东工业大学 ， 结构工程， 2004， 硕士

【摘要】 水泥混凝土是近代最广泛使用的建筑材料，也是当前最大宗的人造材料。由于混凝土具有良好的耐水性、可塑性和原料来源广、生产工艺简单、生产成本低、应用方便等优点一直为工程界所青睐。从发展趋势来看，在今后相当长的时期内水泥混凝土仍起着不可替代的作用，仍将是应用最广、用量最大的建筑材料。但混凝土的自身缺陷也限制了它的应用范围和效果。纤维混凝土可有效的改善混凝土的性能，所以自纤维混凝土问世以来一直受到国内外研究机构和学者的重视。 本文研究了纤维在混凝土中的作用机理，分析、总结提出了提高纤维混凝土性能的有效方法和途径。 首先研究了纤维与混凝土基体之间界面的粘结性能。从理论方面计算了纤维受力后在脱粘和拔出过程中界面剪应力的变化。并采用弹簧粘结单元用有限元方法模拟了纤维与基体的粘结性能。 其次从两方面分析和研究了纤维对混凝土改性的机理。在混凝土硬化过程中纤维改善了混凝土的内部结构，主要表现在减少了混凝土的塑性裂纹和内部微裂纹的数量和尺寸，提高了混凝土材料介质的连续性，从而改善了混凝土的综合性能。在纤维混凝土受力过程中纤维改变了混凝土基体的应力场，从而改变了纤维混凝土的力学性能。 然后运用断裂力学的观点和方法分析了纤维对混凝土的增强、增韧机理。计算过程中考虑了纤维与混凝土之间相互粘结并滑移的真实过程。在纤维混凝土受力过程中，纤维起到阻止混凝土中原有裂纹以及受力过程中新生裂纹扩展的作用。特别是裂纹上桥联纤维的阻裂作用，使纤维混凝土的强度和韧性得到了不同程度的提高。提高纤维与混凝土界面过渡区的密实度，增加纤维的掺量、长度和表面的粗糙度，都可有效的提高纤维混凝土的强度和韧性。从纤维混凝土的破坏机理出发，推导了纤维混凝土抗拉强度的计算公式。 最后总结了纤维对混凝土改性的机理和提高纤维混凝土性能的有效方法，并对进一步的研究工作提出了建议和设想。更多还原

【Abstract】 Concrete is most extensively used as architectural materials in latter day and is the largest artificial materials at present. It is prevalent in civil engineering because of its waterproof, plasticity, abundance, cheapness and easy operation. Thus it is believed that nothing can displace concrete as the most extensive architectural materials in a long time. But in the same time the flaws of the concrete prevent itself from application and good effect. The use of fiber concrete can improve the performance of concrete, so it is concerned more and more by research institutions and scholars since it is come into being.This paper studies the mechanism of changing in fiber concrete and summarizes the methods of improving performance of fiber concrete. The main tasks of the present paper are as follows:Firstly, the interfacial performance between fibers and concrete is studied. Then the change of shear stress in the interface is deduced in theoretical way after the fibers are disengaged and pulled out from concrete. In addition, the spring element is used to simulate the bond between fibers and concrete in FEM.Next, the improvement of fibers to concrete is analyzed from two aspects. On the course of hardening of concrete, the improvement of performance mainly lies in the decrease of plasticity cracks and interior cracks of concrete in quantity and in dimension and the enhancement of medium continuity. The stress field of concrete is altered because of the effect of the fibers, which will change the mechanics performance of concrete.Then, the methods of Fracture Mechanics are adopted to analyze toughness and strength of concrete, which considers the process of slip between fibers and concrete. On the working style of the fiber concrete structure, the fibers make a difference in preventing the fracture cracks from expanding, which improves the strength and toughness to a certain extent. Increasing the density of the transitional field between fibers and concrete structure and increasing the volume fraction, length, and externalroughness of fibers both can improve the strength and toughness of concrete structureeffectively. From the fracture mechanism of fiber concrete structure , some formulations as to the strength of fiber concrete are educed in the paper.Finally, some effective methods of improving working performance of fiber concrete structure are summed up and several suggestions are put forward for further research.更多还原