劈裂裂缝混凝土在海洋潮汐区的氯离子传输

Chloride Transport in Splitting Cracked Concrete at Marine Tidal Zone

研究了不同尺度劈裂裂缝混凝土在海洋潮汐区环境作用下的氯离子浓度分布、氯离子传输以及钢筋锈蚀规律。试验结果表明:劈裂裂缝在制备过程中存在裂缝回复,裂缝宽度应以卸载后位移传感器获得的裂纹宽度值为准。裂缝混凝土氯离子浓度随深度增加而下降,然后在10mm深度以下形成稳定段。裂缝区域稳定段氯离子浓度随裂缝宽度增加而呈指数函数增加,裂缝周边区域稳定段氯离子浓度则随裂缝宽度增加而线性增加;但与裂缝区域氯离子增加幅度相比,其增加幅度不明显。裂缝宽度大于0.05mm,30d海洋暴露后混凝土裂缝面氯离子渗透深度近50mm,沿垂直裂缝面向内平均渗透20mm左右,钢筋表面锈蚀率快速增加。裂缝混凝土氯离子扩散系数与混凝土抗氯离子扩散能力、裂缝密度(包括裂缝的基体宽度/裂缝宽度)、裂缝对氯离子结合性能密切相关。当裂缝密度小于70时,裂缝混凝土氯离子扩散系数线性增加;距裂缝位置越近,混凝土氯离子扩散系数增加越大;裂缝越宽,其对混凝土影响范围越大。

The chloride ion transport in concretes with different size of splitting cracks at marine tidal zone is investigated.The splitting crack widths of concrete are about 0.03 mm,0.05 mm,0.10 mm,0.15 mm and 0.30 mm.The cracked concrete and sound concrete are placed at marine tidal zone for 30 d,and the chloride ion content in crack zone and perimeter zone of concrete,chloride ion penetration depth and steel bar corrosion area are quantitatively determined.It is shown that splitting crack will be recovered when the concrete is unloaded in split test.And the splitting crack width of concrete should be characterized by the value of displacement sensor when the concrete is unloaded in split test.The chloride ion content of cracked concrete decreases with increased depth,and then gets to remain steady from 10 mm to the inner.The relationship between chloride ion content and crack width in the steady zone can be regressed as the exponential function and the linear function for the crack zone and the perimeter zone of concrete,respectively.Due to away from the crack zone,the influence of splitting crack width on accelerated chloride ion ingression in the perimeter zone is less than that in the crack zone.When the splitting crack width is more than 0.05 mm,the chloride ion penetration depth in crack plane and in vertical crack plane of concrete is 50 mm and 20 mm,respectively.And the steel corrosion area enlarges with the increasing crack width.And the chloride diffusion coefficient of cracked concrete is closely related to the resistance capacity to chloride penetration of concrete,crack density（matrix width,crack width）,and chloride binding capacity of concrete.When the crack density of concrete is less than 70,the chloride diffusion coefficient of cracked concrete increases with decreased crack density linearly.The chloride penetration will accelerate near the crack zone.And the raised splitting crack width will lead to its influence area in concrete increased quickly.