The Research Of The Dissolution Behavior Of Concrete And The Steel Corrosion In Sulfate Environment

Concrete durability is having been a major issue focused on the research and in the field of civil engineering, with its damage to concrete structures causing huge economic losses and affecting the development of the country and the lives of people. Calcium dissolution is one of the factors which effect the durability of concrete and presents different effects with different kinds of irons in the real environment.Currently, most researches of calcium dissolution of concrete are only limited in the distilled or deionized water environment. However, there is little studies on concrete corrosion in the ion-containing environment. Therefore, studying the calcium dissolution of concrete in the sulfate environment has more practical significance. Since the calcium dissolution of concrete under the natural conditions is very slow, so the electrochemical acceleration method is used in this test to accelerate concrete corrosion.The influence of the water-cement ratio, admixture, different concentrations of Na2SO4 solution on the behavior of calcium dissolution were studied in this paper. Chemical titration and electrochemical impedance spectra were used to assess the amount of calcium dissolution and concrete resistance value respectively. What’s more, many methods, such as XRD, SEM and MIP, were also used to analysis the concrete microscopic structure before and after the dissolution. The results showed that: the larger of the water-cement ratio, the more pore in the concrete, and the more serious dissolution of the concrete; fly ash and slag improved the ability to resist the concrete dissolution. The calcium dissolution of concrete led to the increase of the big pores and Ca(OH)2 and C-S-H gels dissolved more seriously in the distilled water and Na2SO4 solution, respectively. However, for the directional generated ettringite crystals etc, led to the concrete in the Na2SO4 solution present small pores.Additionally, the effects of concrete dissolution on the steel corrosion in distilled water and 0.5% Na2SO4 solution were discussed by measuring the changes of electrochemical parameters(corrosion potential, polarization resistance, impedance spectroscopy, etc.). The results showed that the reinforced steel corrosion did not occur in a short time after dissolution in distilled water, but presented high risk to rust after dissolution in 0.5% Na2SO4 solution.