Chloride binding of barium-containing zeolite corrosion inhibitor in Portland cement mortar

Abstract

The use of sea sand is limited in reinforced concrete due to the presence of corrosive free chloride ions. In this study, a barium-containing zeolite corrosion inhibitor was designed and added into mortar to improve the chloride binding ability by avoiding the interference of SO42− in forming chloroaluminate salts under the condition of ensuring the necessary setting time of the mortar. Ion dissolution tests showed that the amount of Ba2+ released by the corrosion inhibitor in the first 3 h was only 29.6 mg/L, which avoided the problem of rapid setting of the mortar. The ability of the mortar to bind free chloride ions was assessed by leaching titration, and the sample with 16 wt% corrosion inhibitors showed a 32% increase in the bound chloride ratio compared to the control sample at 28 d. The results of XRD, TG-DTG, 27Al MAS NMR and SEM-EDS tests indicated that the slow-release Ba2+ from the corrosion inhibitor promoted the formation of chloroaluminate by precipitating SO42− in the late hydration stage in the mortar. Electrochemical impedance spectroscopy results further confirmed the effectiveness of the corrosion inhibitor in inhibiting the rusting of the steel bars. This study provides guidance for the use of sea sand resources and the long-term corrosion prevention of reinforced concrete.