裂缝非贯通条件下混凝土结构中氯离子扩散解析

Analysis of Chloride Ion Diffusion in Concrete Structure under Non-penetrating Crack Condition

考虑混凝土裂缝的非贯通条件,根据裂缝深度将带裂缝混凝土结构分为裂缝区和无裂缝区.依据Fick第二定律,建立氯离子在带裂缝混凝土结构中的扩散方程,结合初始条件和边界条件,采用Laplace变换法得到带裂缝混凝土结构中氯离子扩散方程的解析解,并分析裂缝宽度和深度对氯离子分布规律及钢筋混凝土结构耐久寿命影响.结果表明,裂缝的深度越小、宽度越大,则裂缝非贯通条件下的氯离子浓度与裂缝贯通条件下的氯离子浓度差异越大.随着裂缝深度与保护层厚度之比dcr/dc增大,钢筋混凝土结构耐久寿命呈现先减小后增大的变化趋势;当dcr/dc=1.0时,结构耐久寿命取得最小值;当dcr/dc>1.6时,结构耐久寿命可近似按裂缝贯通时的情况计算.

According to the crack depth ,concrete structure is divided into two parts,cracks zone and sound zone. Based on Fick’s second law, diffusion equation of chloride ions in cracked concrete structure is established. Combined with the initial and boundary conditions, analytical solution of the diffusion equation of chloride ions in cracked concrete structure was derived by the Laplace transform method. Finally, the influence of crack width and depth on the distribution of chloride ions and the durability life of reinforced concrete structures was analyzed. The results show that the smaller the depth and the larger the width of the crack, the greater the difference between the chloride ion concentration in the case of crack non-penetrating crack and the chloride ion concentration in the case of penetrating crack. With the increase of the ratio of crack depth to cover depth, the service life of reinforced concrete structure decreases first and then increases. When dcr/dc=1.0, the service life approaches to the minimum. When dcr/dc>1.6, the service life can be approximately calculated according to the condition of penetrating crack.