疲劳荷载和冻融循环耦合作用下路面混凝土微裂缝扩展行为

为了定量表征与分析在疲劳荷载和冻融循环耦合作用下路面混凝土内部裂缝的演化规律, 采用SEM与形态学图像分割法对不同疲劳荷载和冻融循环耦合阶段的混凝土微裂缝进行提取, 采用Image-Pro Plus对微裂缝进行量化, 采用灰色关联法研究了裂缝特征参数与耦合作用后路面混凝土弯拉强度损失的相关性。分析结果表明: 路面混凝土内部存在平均宽度为13μm、最大长度为144μm的原始微裂缝, 耦合作用下裂缝的演化沿长度方向为延伸和断裂交替变化, 沿宽度方向为扩张和收缩交替变化, 混凝土破坏时裂缝最大长度达到352.64μm, 裂缝平均宽度达到15.4μm; 当冻融循环150次时, 裂缝面积密度显著增大, 与原始微裂缝相比, 混凝土破坏时裂缝面积密度增大了6.7倍; 耦合作用下路面混凝土裂缝分形维数、平均宽度、最大长度与弯拉强度的相关性较高, 灰色关联度分别为0.957、0.954、0.871;通过回归分析建立了路面混凝土弯拉强度损失与裂缝结构参数之间的方程, 弯拉强度损失与裂缝分形维数、平均宽度、最大长度之间存在较好的线性相关性, 相关系数达到0.97。

Micro-crack propagation behavior of pavement concrete subjected to coupling effect of fatigue load and freezing-thawing cycles

In order to quantitatively characterize and analyze the evolution laws of pavement concrete internal cracks under the coupling effect of fatigue load and freezing-thawing cycles, the SEM and the morphological image segmentation method were used to extract the micro-crack patterns, the Image-Pro Plus was used to quantify the micro-crack structure, and the relationship between the crack parameters and the loss of flexural strength under the coupling effect was studied by using the grey correlation analysis method.Analysis result shows that there are original micro-cracks in pavement concrete, the average width is 13 μm, and the maximum length is 144 μm.Under the coupling effect, the evolution of pavement concrete cracks along the length direction is the alternative process of extension and fracture, while the crack evolution along thewidth direction is the alternative process of expansion and contraction.When the concrete is destroyed, the maximum length of crack reaches 352.64 μm, and the average width of crack reaches 15.4 μm.After 150 times freezing-thawing cycles, the crack area density increases significantly, and is 6.7 times larger than the density of original micro crack when concrete is destroyed.The flexural strength of pavement concrete is greatly related to the fractal dimension, average width and maximum length of the crack under the coupling effect, and the grey correlation coefficients are 0.957, 0.954 and 0.871 respectively.Based on the regression analysis, the equation between the flexural strength loss and crack structural parameters of pavement concrete is established, there is good linear correlation between the flexural strength loss and the fractal dimension, average width, maximum length of crack, and the correlation coefficients reach 0.97.