Anion capture and exchange by functional coatings: New routes to mitigate steel corrosion in concrete infrastructure. (November 2017)

• Record Type: Journal Article
• Authors: Falzone, Gabriel; Balonis, Magdalena; Bentz, Dale; Jones, Scott; Sant, Gaurav
• Is Part Of: Cement and concrete research. Volume 101(2017)
• Page Start: 82
• Page End: 92
• Publication Date: 2017-11
• Subjects: (C) corrosion -- (C) finite element analysis -- (D) calcium aluminate cement -- (D) chloride -- (−) calcium nitrate; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2017.08.021
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: Chloride-induced corrosion is a major cause of degradation of reinforced concrete infrastructure. While the binding of chloride ions (Cl − ) by cementitious phases is known to delay corrosion, this mechanism has not been systematically exploited as an approach to increase structural service life. Recently, Falzone et al. [ Cement and Concrete Research 72, 54–68-(2015)] proposed calcium aluminate cement (CAC) formulations containing NO3 -AFm to serve as anion exchange coating s that are capable of binding large quantities of Cl − ions, while simultaneously releasing corrosion-inhibiting NO3 − species. To examine the viability of this concept, Cl − binding isotherms and ion-diffusion coefficients of a series of hydrated CAC formulations containing admixed Ca(NO3 )2 (CN) are quantified. This data is then input into a multi-species Nernst-Planck (NP) formulation, which is solved for a typical bridge-deck geometry using the finite element method (FEM). For exposure conditions corresponding to seawater, the results indicate that Cl − scavenging CAC coatings (i.e., top-layers) can significantly delay the time to corrosion (e.g., 5 ≤ d f ≤ 10, where d f is the steel corrosion initiation delay factor [unitless]) as compared to traditional OPC-based systems for the same cover thickness; as identified by thresholds of Cl − /OH − or Cl − /NO3 − (molar) ratios in solution. The roles of hindered ionic diffusion, and the (re)passivation of the reinforcing steel rendered by NO3 − are also discussed.