粉煤灰对受弯开裂钢筋混凝土内氯离子侵蚀的影响

为了研究粉煤灰掺量对受弯开裂钢筋混凝土中氯离子侵蚀过程的影响，采用三点受弯的方法将粉煤灰掺量(质量分数)分别为0%,15%和30%的混凝土梁进行两两自锚，并将不同开裂状态下的试验梁放置于5%(质量分数)的NaCl溶液中进行干湿循环侵蚀试验.结果表明：干湿循环作用下，受弯开裂混凝土的表层对流区深度在10~20mm，且随着裂缝宽度的增加，对流区深度逐渐增大；混凝土的氯离子渗透性能随着弯曲裂缝宽度的增大而提高；粉煤灰掺量在15%以上时能有效改善开裂混凝土的抗氯离子渗透性能，其等效氯离子扩散系数是普通混凝土的1/8~1/6；扩散分析时，混凝土损伤劣化效应系数K与裂缝宽度w，粉煤灰掺量f可用指数关系进行拟合.

Influence of Fly Ash Content on Chloride Corrosion in FlexurallyCracked Reinforced Concrete

In order to study the influence of fly ash on the chloride corrosion in flexurally cracked reinforced concrete, several concrete beams with the mass ratio of fly ash to cementitious material of 0%, 15% and 30% were self anchored in a three point bending mode. Under the sustained flexural loads, these beams with different cracks were immersed in 5% NaCl solution under the condition of dry wet cycles. The results show that under the dry wet cycles, the crack depth at convection region in the flexurally cracked concrete is about 1020mm, which increases gradually with the increase of crack width. The resistance of chloride permeability in concrete improves with the increase of crack width. More than 15% of fly ash content can effectively improve the resistance of chloride permeability of cracked concrete, and its equivalent chloride diffusion coefficient may reduce to 1/8~1/6 of that of ordinary concrete. For the chloride diffusion in cracked concrete, there is an exponential relationship between the damage coefficient, crack width and fly ash content.