基于断裂理论的玄武岩纤维混凝土双K断裂参数及力学性能研究

Double-K Fracture Parameters and Mechanical Performance of Concrete Incorporating Basalt Fiber

混凝土基体中纤维材料的加入可以有效抑制开裂,提升其抗变形能力。为深入了解纤维对提升混凝土抗开裂破坏能力的作用,基于断裂理论并通过试件三点弯曲试验,对掺入不同长度和体积分数玄武岩纤维的混凝土在开裂破坏时的力学性能进行了研究,同时通过扫描电镜技术观察纤维的微观断裂特征。结果表明,掺入玄武岩纤维对试件劈裂抗拉强度和抗折强度均有明显改善,较素混凝土试件分别提升29%和22%,其中纤维长度对劈裂抗拉强度影响较小,对抗折强度影响明显;长纤维试件具有较高的韧性和抑制裂缝扩展能力,短纤维试件在荷载施加后期易产生明显的应变软化现象,表现出显著的脆性断裂特征,而含有中等纤维的试件则同时兼具最高的抵抗初裂和抑制裂缝扩展的能力。研究内容对指导实际工程改善纤维混凝土抗裂性能有一定理论价值。

The abilities of anti-crack and deformation of concrete could be significantly prohibited by adding different kinds of fibers. In order to further analyze the influence of fibers on promoting the abilities of anti-crack and damage of concrete materials,the three-point bending test of specimens based on theory of fracture was conducted. The influence of basalt fiber with different length and volume percentage to the mechanical properties of concrete materials during the process of fracture failure was tested. At the meantime,the characters of micro-cracks of basalt fibers were also investigated by SEM technology. The results shown that the splitting tensile strength and flexural strength of concrete adding basalt fibers could be greatly improved. And compared with plain concrete,the splitting tensile strength and flexural strength of basalt fiber concrete were increased by 29% and 22%,respectively. The length of fiber has less effect on splitting tensile strength but prominent effect on flexural strength. The concrete with long fiber has higher toughness and better capabilities of prohibiting the propagation of cracks,while the concrete with mid length fiber could control the incipient cracks and prohibit the cracks propagate to the best effects. The concrete with shorter fiber shown obvious phenomenon of strain softening and characters of brittle rupture. This result has certain theoretical value for conducting practical engineering to improve the ability of anti-cracks of fiber concrete.