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通过室内氯离子侵蚀加速试验及氯离子分布测试,结合Fick第2定理拟合出梯度结构混凝土(GSC)的氯离子浓度扩散系数,以研究面层体积分数、加速试验龄期对扩散系数的影响;采用压汞技术测试面层材料与结构层材料的孔结构参数,分析氯离子扩散系数与孔结构之间的关系。结果表明:GSC体系的氯离子扩散系数随面层体积分数的增加而下降,并逐渐趋于平缓;GSC体系氯离子扩散系数则随加速试验龄期的延长而减小,最后也趋于稳定;与面层体积分数V=0试件相比,其它GSC试件具有更大的时间衰减系数值,说明其抵抗氯离子侵蚀的能力更好。最后根据相似性理论,建立了考虑面层体积分数变化的GSC氯离子扩散系数时变模型,分析显示,与结构层材料相比,面层材料具有较低的孔隙率及最可几孔径,使得孔的曲折性越大、连通性越低,因而面层材料具有更低的扩散系数。
Based on the chloride ion acceleration test and the chloride ion distribution test, the chloride ion concentration diffusion coefficient of Gradient Concrete (GSC) was fitted by Fick’s second theorem to study the effect of surface volume fraction and accelerated test age on the diffusion coefficient The pore structure parameters of surface material and structure layer were tested by mercury intrusion technique, and the relationship between chloride ion diffusion coefficient and pore structure was analyzed. The results showed that the chloride ion diffusion coefficient of GSC decreased with the increase of surface volume fraction and gradually became more gentle. The chloride ion diffusion coefficient of GSC decreased with the extension of accelerated test period and finally stabilized. Compared with the V = 0 specimen, the other GSC specimens have a larger value of time attenuation coefficient, indicating that they are more resistant to chloride ion erosion. Finally, according to the similarity theory, a time-varying model of GSC chloride ion diffusion coefficient considering the changes of the volume fraction of the surface layer is established. The analysis shows that the surface material has a lower porosity and the most probable pore size compared with the material of the structural layer, The greater the zigzag of the holes, the lower the connectivity and thus the lower diffusion coefficient of the facing material.