初始裂缝宽度对混凝土自修复效果的影响

Influence of initial crack width on self-healing effect of concrete

为了研究初始裂缝宽度对混凝土自修复效果的影响,设计了3组不同裂缝宽度(0.4~0.6、0.6~0.8、0.8~1.8 mm)条件下的混凝土自修复效果试验,并采用图像显微镜、扫描电子显微镜(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)等微观表征手段分析了裂缝处填充物的微观样貌和组成。通过图像显微镜观测发现,自修复混凝土的裂缝修复效果随着初始裂缝宽度的增大而降低。裂缝宽度为0.4~0.6 mm时,自修复效果较好,裂缝修复率达90.3%,可修复最大裂缝宽度为0.594 mm;当裂缝宽度为0.8~1.8 mm时,自修复效果明显下降,修复率仅为31.1%,可修复最大裂缝宽度为1.654 mm。SEM分析表明,固载微生物的膨胀珍珠岩既可以在混凝土未开裂前对微生物起到保护作用,又能在开裂后为微生物的生长代谢提供良好的物质能量交换空间,有利于碳酸钙沉积物的生成,提高混凝土的裂缝自修复效果。XRD分析表明,混凝土自修复机理是裂缝处有碳酸钙晶体的生成,并且距混凝土表面较近(距混凝土裂缝表面约10 mm)区域的裂缝中填充物为方解石,而裂缝深处(距混凝土裂缝表面约10~30 mm)的填充物为针状的文石。

In order to study the effect of initial crack width on the self-healing effect of concrete,three sets of concrete self-healing effect tests under the conditions of different crack widths(0.4-0.6 mm,0.6-0.8 mm,0.8-1.8 mm)were designed.Image microscope,scanning electron microscope(SEM),X-ray diffraction(XRD)and other microscopic characterization methods were applied to analyze the microscopic appearance and composition of the filling at the crack.Through image microscope observation,it is found that the crack heal effect of self-healing concrete decreases with the increase of the initial crack width.The self-healing effect is good when the crack width is within the range of 0.4-0.6 mm,the crack heal rate is 90.3%,and the maximum healable crack width is 0.594 mm.When the crack width is within the range of 0.8-1.8 mm,the self-healing effect is significantly reduced,and the heal rate is only 31.1%,and the maximum healable crack width is 1.654 mm.SEM analysis shows that the microbial-loaded expanded perlite can not only protect the microbes before the concrete is cracked,but also provide a good material and energy exchange space for the growth and metabolism of the microbes after cracking,which is beneficial to the calcium carbonate deposits and improves the self-healing effect of concrete cracks.According to XRD analysis,the self-healing mechanism of concrete is the formation of calcium carbonate crystals in the cracks.The filling in the cracks near the surface of the concrete(about 10 mm from the concrete crack surface)is calcite,while the deep part of the crack(about 10-30 mm from the concrete crack surface)is filled with needle-shaped aragonite.