冻融条件下玄武岩纤维混凝土断裂韧度研究

发布时间：2018-10-25 11:40

【摘要】：该文使用数字图像相关方法实时观测三点弯试验中切口混凝土梁全场变形,分析混凝土梁断裂破坏过程中水平位移和应变的变化规律,基于切口处水平位移和应变变化规律确定起裂荷载,并研究冻融循环次数和纤维掺量对混凝土起裂韧度、失稳韧度、临界开口位移的影响,结果表明:对于C30混凝土而言,起裂韧度和失稳韧度随冻融次数的增加而减小,降幅约为0.6 MPa·m~(1/2)~0.80 MPa·m~(1/2),两种韧度随玄武岩纤维掺量增加有小幅增加,最大增幅分别约为0.1 MPa·m~(1/2)和0.2 MPa·m~(1/2),说明玄武岩纤维能提高C30混凝土的抗冻性,但提高程度是一定的,玄武岩纤维不能完全抑制冻融对混凝土的损伤;纤维掺量对失稳韧度的提高幅度要比起裂韧度大;起裂韧度增益比和失稳韧度增益比都随纤维掺量增加先增大后减小,两种韧度增益比均在纤维掺量为2.0 kg/m~3时最大,因此,在混凝土强度等级为C30时,2.0 kg/m~3可作为最佳纤维掺量;临界开口位移随冻融次数增加而增大,随纤维掺量变化效果不明显,与纤维增强作用相比冻融损伤是影响断裂过程变形性能的主要因素;最后在试验结果的基础上,建立了起裂韧度和失稳韧度随纤维掺量和冻融次数的拟合模型。
[Abstract]:In this paper, digital image correlation method is used to observe the full-field deformation of notch concrete beam in three-point bending test in real time, and the variation law of horizontal displacement and strain during fracture and failure of concrete beam is analyzed. Based on the horizontal displacement and strain variation at the notch, the crack initiation load is determined, and the effects of freeze-thaw cycle times and fiber content on the crack initiation toughness, instability toughness and critical opening displacement of concrete are studied. The results show that: for C30 concrete, the crack initiation toughness, instability toughness and critical opening displacement are affected by the number of freeze-thaw cycles. The initial fracture toughness and instability toughness decreased with the increase of freezing and thawing times, about 0.6 MPa m2 ~ 0.80 MPa m ~ (1 / 2), and the two types of toughness increased slightly with the increase of basalt fiber content. The maximum increases are about 0.1 MPa m2 and 0.2 MPa m2, respectively, indicating that basalt fiber can improve the frost resistance of C30 concrete, but the degree of improvement is certain, basalt fiber can not completely inhibit the damage to concrete caused by freeze-thaw. The increase of the initial toughness gain ratio and the instability toughness gain ratio increased firstly and then decreased with the increase of fiber content, and the maximum toughness gain ratio of the two fibers was 2. 0 kg/m~ 3, so the ratio of initial toughness gain and instability toughness gain ratio increased with the increase of fiber content, and the ratio of initial toughness gain ratio and instability toughness gain ratio increased firstly and then decreased with the increase of fiber content. When the strength grade of concrete is C30, 2.0 kg/m~3 can be regarded as the best fiber content, and the critical opening displacement increases with the increase of freeze-thaw times, but the effect is not obvious with the fiber content. Freezing and thawing damage is the main factor affecting the deformation property of fracture process compared with fiber reinforcement. Finally, a fitting model of initial crack toughness and instability toughness with fiber content and freeze-thaw number is established on the basis of experimental results.
【作者单位】：内蒙古工业大学土木工程学院;
【基金】：国家自然科学基金项目(11362013)
【分类号】：TU528

【相似文献】