Study Of The Dissolution Behavior And Its Influencing Factors Of Chloride Ion Of Mortar

Corrosion of reinforcement is one of the most important reasons to reduce the durability of reinforced concrete. And one of the key reasons causes the concrete corrosion is the diffusion of chloride ions. When the free chloride ions reach the chloride threshold level of corrosion in pore solution of concrete, the steel rebar inside reinforce concrete structures is susceptible to corrosion. Therefore, there is an important role for improving the corrosion resistance of concrete by studying the dissolution behavior of chloride ions in mortar. To determine the dissolution behavior of chloride ions in mortar with different water/binder ratio and different mineral admixtures at different curing ages, the rapid chloride ion permeability test was carried out in this paper and the content of chloride ions in the process of static and dynamic dissolution at the same time. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and the composition and type of crystal in mortar, and then analyzed the relationship between the dissolution behavior of chloride ions and the hydration products of the mortar. The conclusions from experimental results are as follows:(1) The distributions of aggregate and cement materials are uneven of mortar on the water/binder ratio of0.50by traditional vertical molding method to form. However, the distributions of aggregate and cement materials are uniform of mortar on the water/binder ratio of0.50by rotating device molding method to form. And the optimum speed of the rotating device is0.1r/min. During this speed, the distributions of inside pore structure are relatively dense of mortar.(2) In the rapid chloride penetration experiment, the ability of resistance to chloride ions penetration increase with the reduction of water/binder ratio, the increase of the curing age, the adjunction of mineral admixtures and the increase of the addition of mineral admixtures. The effect of the ability of resistance to chloride ions penetration increase with the increase of the curing age is better than the reduction of water/binder ratio and the adjunction of mineral admixtures.(3) The binding chloride ions of mortar dissolved to form the soluble chloride ions in the process of static and dynamic dissolution, and the content of the soluble chloride ions is related with the content of chloride ions in the dissolution equilibrium. The soluble chloride ions content increased with the increase of chloride ions content in the dissolution equilibrium.(4) Water/binder ratio, mineral admixtures and curing age could effect on static and dynamic dissolution behavior of chloride ions in mortar. The reduction of water/binder ratio, the increase of the curing age, the adjunction of mineral admixtures and the increase of the addition of mineral admixtures do not change the overall variation of the dissolution behavior of chloride ions of mortar, but reduce the starting dissolution content of chloride ions and the chloride ions content in the dissolution equilibrium, and improve the ability of curing chloride ions of mortar. The effect of the chloride ions content in the dissolution equilibrium increase with the increase of the curing age is best, and the increase of the addition of mineral admixtures is followed, and the reduction of water/binder ratio is worst.(5) The dissolution behavior of chloride ions in mortar has the same variation in the different diffusion depth, and the starting dissolution content of chloride ions reduce with the increase of the diffusion depth, but there is almost no change to the chloride ions content in the dissolution equilibrium.(6) From the analysis of the microstructure and the composition and type of crystal in mortar, it can be concluded that the extension of curing age and the pozzolanic effect of mineral admixtures can make the hydration fully, and reduced the content of hydration products AFt and Ca (OH)2crystal which generate more hydration products, and improve the content of Friedel’s salt, which can make the microstructure of concrete much more uniform and compactness and effectively reduce the chloride ions content in the static and dynamic dissolution equilibrium.