Concrete surface treatment and chlorine ions cause corrosion of steel

Research data show that the sodium chloride and concrete components together into the new mixed concrete, when the chloride content of cement quality 0.4%~0.8%, steel corrosion significantly.

Ren Zhaojun with water to cement ratio 0.6 of the concrete, the dosage of sodium chloride is 15kg/m University, study the influence of internal environment of chlorine ion of reinforcement corrosion in concrete. After 2 weeks, 10 weeks in the laboratory, and the surface waterproofing treatment was carried out. After that, the direct test was finished in the laboratory, and the measurement results were shown in Figure 6.13.

From Fig. 6.13 can be seen, the value of two groups of specimens of half cell potential is at an early stage with the growth time and negative to reduce, the corrosion current density values decreased with the increase of the time, and 17 weeks after the relative humidity of the concrete internal moisture and environmental balance, because of doped chloride ion of the concrete reinforcement corrosion in increased and the corrosion current density of the two groups of specimens of half cell potential value and reinforced value were similar. In addition, the test results of the weight loss method, half cell potential method and the linear polarization method are in agreement with the actual corrosion of reinforcement. The test results show that the surface waterproofing treatment of chloride ions in the concrete reinforcement of the corrosion effect is not, can not effectively prevent or reduce the corrosion of steel bars.

Water cement ratio of 0.4 and 0.6 concrete. When the dosage of sodium chloride is 15kg/m University. Under the condition of dry wet circulation internal environment of chlorine ion of reinforcement corrosion in concrete influence test results are shown in Figure 6.14. In the trial, formed and cured after 1 week. In the laboratory natural drying for 3 weeks, surface waterproofing treatment and try to top of the container into the water, soaking 8h, water poured out, specimens in the laboratory natural drying 1 week and the steps to repeat the cycle until the trials ended.

It can be found from the figure that, for the two kinds of water cement ratio, the half cell potential absolute value and the corrosion current density of the steel bar are significantly larger than that of the water treatment. This shows that, under dry and wet conditions, compared with the surface waterproof, the surface waterproofing treatment will have a better effect of inhibiting the corrosion of steel in concrete. The reason is that solution of silane waterproofing agent can significantly reduce the water absorption of concrete, so that water and with water as the carrier of material are difficult to sucked into the concrete, also concrete water can water vapor free evaporation out, make the concrete to keep dry. In this way, the water content in the concrete is obviously lower than that of the concrete which is not waterproof, so it can restrain the corrosion of the steel bar to a certain extent.