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分析干湿交替对受弯开裂混凝土梁内氯离子侵蚀的影响,建立考虑表层对流区影响的氯离子等效扩散模型,并借助氯盐干湿循环试验对此模型进行验证。经过30个干湿循环后,采用快速氯离子含量检测(RCT)法,对各裂缝处及其周围混凝土内自由氯离子浓度进行测定。试验结果表明:干湿交替下,完好及受弯开裂混凝土的表层对流区深度在10~15 mm;弯曲裂缝(宽度不大于0.339 mm)截面处,对流区以内混凝土同一深度处自由氯离子浓度比完好处显著提高,且同一裂缝处的浓度分布符合扩散的基本规律;裂缝周围一定范围内混凝土的自由氯离子浓度随距裂缝横向距离的增大而减小,超过一定范围后,弯曲拉应力对混凝土氯离子渗透性能有一定的提高作用;经回归,裂缝处(宽度不大于0.339 mm)等效氯离子扩散系数D eq(t)与裂缝宽度w之间存在二次函数关系。
The effect of alternating wetting and drying on chloride ion erosion in bending and debonding concrete beams was analyzed. An equivalent chloride diffusion model considering the effect of surface convection zone was established. The model was validated by the chloride wet-dry cycle test. After 30 wet-dry cycles, the free chlorine ion concentration in concrete at and around the cracks was measured by the rapid chloride content test (RCT) method. The experimental results show that the ratio of free chlorine ion concentration at the same depth of the concrete in the convection zone at intact and bent concrete with the depth of 10 ~ 15 mm and the bending cracks (width less than 0.339 mm) And the distribution of the same crack is in accordance with the basic law of diffusion. The concentration of free chlorine in the concrete within a certain range around the crack decreases with the increase of the transverse distance from the crack. When the bending strength exceeds a certain range, the bending tensile stress The chloride ion permeability of concrete increases to a certain extent. After regression, there is a quadratic function between the equivalent chloride diffusion coefficient D eq (t) and the crack width w at the crack (width less than 0.339 mm).