滨海饱和混凝土中氯离子传输行为的细观模拟研究

Mesoscopic simulation study on chloride lon transport behavior in marine saturated concrete

为探究饱和混凝土中氯离子传输规律,建立考虑不同混凝土配合比且含有浆体、骨料和界面过渡区的混凝土细观模型,分别计算氯离子在一维和二维扩散时的浓度,并与试验结果进行对比。分析不同水灰比和水化度对氯离子扩散的影响,并针对海岸线环境中钢筋混凝土结构的钢筋初始锈蚀时间进行预测。研究结果表明:氯离子扩散的细观模型计算时应考虑界面过渡区,且界面过渡区厚度取值为80μm;氯离子浓度扩散的细观模型计算值与试验结果吻合较好,且氯离子的扩散性随着混凝土水灰比的增大而显著增大,但随着水化度的增大而变小;氯盐环境中钢筋表面初始锈蚀点的位置是不固定的。在相同条件下,氯离子一维扩散时,钢筋初始锈蚀时间是二维扩散的2.31~3.24倍;当保护层厚度从50mm增加到60mm时,在一维扩散中且水灰比分别为0.4、0.5和0.6时,混凝土中钢筋的初始锈蚀时间分别延长28.00%、10.90%和18.50%,在二维扩散中且水灰比为0.4、0.5和0.6时,初始锈蚀时间则分别延长52.42%、7.45%和56.65%。该结果可为海岸线环境中钢筋混凝土结构的钢筋初始锈蚀时间的预测提供借鉴。

To investigate the chloride ion transport law in saturated concrete,a meso-scale model for concrete that considering different concrete mixtures with cement paste,aggregate and interfacial transition zones is established.Through the established model,the chloride ions concentrations are calculated in one-dimensional and two-dimensional diffusion,respectively.The simulation results are used to compare with the experimental results.The effects of water-cement ratio and degree of hydration on chloride ion diffusion are analyzed and the initial corrosion time of steel reinforcement in reinforced concrete structures is predicted in coastal environments.The comparison results show that when calculating in the meso-scale model for chloride ion diffusion,it is important to consider the interfacial transition zone,with a thickness of 80μm.The calculated values of the meso-scale model of chloride ion concentration diffusion are in good agreement with the experimental results..In a chloride-rich environment,the initial corrosion point on the surface of steel reinforcement is not fixed.Under the same conditions,the initial corrosion time of steel reinforcement in one-dimensional diffusion of chloride ions is 2.31-3.24 times that of two-dimensional diffusion.when the thickness of the protective layer is increased from 50 mm to 60 mm and water/cement ratios are 0.4,0.5,and 0.6,the initial corrosion time of steel is extends by 28.00%,10.90%,and 18.50%in one-dimensional diffusion and is extended by 52.42%,7.45%and 56.65%in two-dimensional diffusion,respectively.The results in this study can be useful for predicting the initial corrosion time of steel reinforcement in coastal environments.