养护湿度对混凝土内氯离子传输的影响

Impact of curing humidity on chloride transportation in concrete

摘要:

为得出早期养护湿度对混凝土内腐蚀介质传输的定量影响，以氯盐侵蚀为例，从水化度及孔隙率角度分析了混凝土养护湿度与氯离子扩散系数之间的相互关系，建立了不同养护湿度下氯离子扩散系数的计算模型.对制作的普通混凝土及掺纤维混凝土试件采用不同湿度进行养护，然后将试件在NaCl溶液中分别浸泡60 d和180 d，测试得到的氯离子质量分数表明，早期养护湿度越大，混凝土的表观氯离子扩散系数越小.相对于正常浇水养护，饱水养护可降低氯离子扩散系数10%~20%，而不养护将使氯离子扩散系数增大14%~29%.纤维的加入能减弱不正常养护对混凝土耐久性的影响.最终利用试验数据回归得出了模型中不同材料所对应的参数，给出了不同湿度养护后混凝土的表观氯离子扩散系数计算公式.

Abstract:

To obtain the effects of curing humidity on corrosive medium transporting into concrete, a model between curing humidity and chloride diffusion coefficient was developed according to their relationships with hydration degree and porosity, which was exposed in chloride solution. An experiment was designed to verify the correct of the model, which included ordinary performance concrete and concrete mixed with fibers. All of the specimens were cured in different humidity for 28 days, and then immersed in 8% NaCl solutions for 60 and 180 days respectively. The results showed that reduction of curing humidity could increase the concentration and diffusion coefficient of chloride ions. Saturating curing can reduce the chloride diffusion coefficient by 10~20%, as dry curing increased the value about 14%~29%. This process can be slowed by mixing polypropylene and steel fibers into concrete. The material coefficients were fitted according to the test results and predicted formulas of apparent chloride diffusion coefficient were provided for the concrete after different humidity's curing.