一般干湿循环对混凝土力学性能及抗氯离子渗透性能的影响

为了解我国淡水区干湿循环作用下混凝土构件的性能变化情况，研究模拟了无盐害共同作用的一般干湿循环环境，测试一般干湿循环前后混凝土的抗压强度表征力学性能，动弹模量表征内部损伤情况以及非稳态氯离子迁移系数表征混凝土的抗氯离子渗透能力。结果表明，干湿循环后，混凝土抗压强度有所增长，内部出现损伤，抗氯离子侵蚀性能增强。研究同时进行了混凝土孔结构参数的测试，混凝土孔隙率减小、平均孔径变小、凝胶孔含量增多以及大孔含量减少，使得混凝土变得更加密实，是导致混凝土强度提高的主要原因。混凝土内部损伤可能是由于干湿循环作用下混凝土内部出现了微裂纹，并非是孔结构变差导致。干湿循环后混凝土临界孔径的减小是其抗氯离子侵蚀性能增强的主要原因。

Influence from normal dry-wet cycle on concrete mechanical performance and resistance to chloride ion penetration

In order to understand the change of the performance of the concrete members under the effect of dry-wet cycle within the freshwater regions in China，the normal environment of dry-wet cycle without the common effect of salt injury is simulatively studied herein; from which the compressive strength-characterized mechanical performance of concrete，the dynamic elastic modulus-characterized internal damage and the unsteady chloride migration coefficient-characterized resistance of concrete to chloride ion penetration before and after the normal dry-wet cycle are tested. The result shows that the compressive strength is increased to some extent along with occurrence of internal damage and increase of resistance to chlorine ion erosion，meanwhile，the pore structural parameters of concrete are tested as well. It is indicated that the concrete porosity is decreased along with smaller mean pore size，increased gel pore content and decrease of large pore content，which makes concrete more compacted and is also the main causation of the increase of concrete strength. The internal damage of concrete is possibly caused by the micro-fissures occurred inside concrete under the effect of dry-wet cycle and is not caused by pore structure variation. The decrease of the critical pore size of concrete after dry-wet cycle is the main cause of the increase of its resistance to chlorine ion erosion.