碳化—干湿循环作用下风积沙混凝土氯离子传输试验研究

我国西北地区有大量盐湖分布，加之冬季除冰盐的使用，使这种环境下混凝土工程的气液交换区经常受到干湿循环和碳化的双重作用，这部分混凝土比一般环境下的混凝土更容易发生钢筋锈蚀。进行了风积沙混凝土在干湿循环和碳化作用下氯离子侵蚀试验研究，通过分析自由氯离子含量和分布规律、氯离子扩散系数以及时间依赖性与碳化时间的关系，深入研究了风积沙混凝土在碳化和干湿循环作用下氯离子的传输规律。结果表明：碳化作用阻碍了氯离子向内部的迁移速度，且碳化时间越长氯离子扩散系数越小，对混凝土抗氯离子侵蚀起到了积极作用；干湿循环作用前期加速了氯离子侵入，中后期由于形成的盐结晶填充了孔隙，增大了混凝土的密实度，阻碍了氯离子继续向内侵蚀，但结晶应力产生的裂缝却使表层氯离子含量增加。

Chloride ion transport in aeolian sand concrete under carbonization and dry-wet cycle

A large number of salt lakes distributes in northwest China, and deicing salt is widely used in winter, so the gas-liquid exchange area of the projects in this area is often subjected to the dual effects of dry-wet cycle and carbonization, which makes the affected concrete more prone to reinforcement corrosion than that in general environment. In order to investigate the transport law of chloride ions in aeolian sand concrete under carbonization and dry-wet cycle, chloride ion corrosion experiments were carried out to analyze the content and distribution law of free chloride ions, the diffusion coefficient of chloride ions and the relationship between time dependence and carbonation time. The results showed that carbonation hindered the transport speed of chloride ions to the inner part of the concrete, the longer the carbonation time was, the lower the chloride diffusion coefficient became, so the carbonization played a positive role in the resistance of chloride ion corrosion. In the early stage of the dry-wet cycle, the chloride ion intrusion was accelerated; then in the middle and late stages, the salt crystals formed in the pores filled up the space in the pores, which increased the density of the concrete and prevented the inward intrusion of chloride ions. However, the cracks caused by the crystal stress increased the chloride ion content in the surface layer.