氯离子在饱和混凝土裂缝中的扩散系数分析

STUDY ON CHLORIDE DIFFUSIVITY COEFFICIENT IN CRACKS WITHIN SATURATED CONCRETE

裂缝的存在加速混凝土中氯离子的侵蚀速度,进而加快钢筋混凝土结构力学性能的劣化速度,因此钢筋混凝土结构耐久性设计中需要考虑裂缝的影响。现有文献中关于裂缝对氯离子扩散行为定量影响的试验结果具有很大的离散性,给出的拟合公式带有局限性。对此,该文建立了一个统一的裂缝中氯离子扩散系数Dcr与裂缝宽度wcr之间的定量关系式。该关系式各参数具有明确的物理意义,对应的曲线圆滑且不存在拐点。与已有试验数据吻合良好,验证了公式的合理性。数值模拟了开裂混凝土中氯离子扩散行为,数值结果与文献结果吻合良好,证明了方法的有效性。

Cracks within concrete can accelerate the ingress velocity of chloride ions into concrete, causing the accelerated degradation of mechanical performances of reinforced concrete structures. The effects of cracks are thus needed to be taken into account in the durability design of reinforced concrete structures. In the available publications, the experimental observations obtained from different researchers present large discrepancy on the quantitative effect of cracks on chloride diffusivity. And therefore the corresponding fitting formulas should have some limitations. In light of this, a unified quantitative relation between the chloride diffusion coefficient Dcr in crack and crack width wcr is developed. The parameters in the proposed formula have their own physical meanings, and the corresponding curve of the formula is smooth without inflection point. The good agreement between the present theoretical results and the available test data illustrates the rationality of the developed formula. Finally, the chloride diffusivity in cracked concrete is studied and simulated by using FE method. The obtained simulation results are consistent with those in the available publications, indicating the effectiveness of the present method.