Abstract
Chloride penetration is among the main causes of corrosion initiation in reinforced concrete (RC) structures producing premature degradations. Weather and exposure conditions directly affect chloride ingress mechanisms and therefore the operational service life and safety of RC structures. Consequently, comprehensive chloride ingress models are useful tools to estimate corrosion initiation risks and minimize maintenance costs for RC structures placed under chloride-contaminated environments. This paper first presents a coupled thermo-hydro-chemical model for predicting chloride penetration into concrete that accounts for realistic weather conditions. This complete numerical model takes into account multiple factors affecting chloride ingress such as diffusion, convection, chloride binding, ionic interaction, and concrete aging. Since the complete model could be computationally expensive for long-term assessment, this study also proposes model simplifications in order to reduce the computational cost. Long-term chloride assessments of complete and reduced models are compared for three locations in France (Brest, Strasbourg and Nice) characterized by different weather and exposure conditions (tidal zone, de-icing salts and salt spray). The comparative study indicates that the reduced model is computationally efficient and accurate for long-term chloride ingress modeling in comparison to the complete one. Given that long-term assessment requires larger climate databases, this research also studies how climate models may affect chloride ingress assessment. The results indicate that the selection of climate models as well as the considered training periods introduce significant errors for mid- and long- term chloride ingress assessment.
Highlights
Chloride ingress is among the principal causes of deterioration of reinforced concrete (RC) structures in chloridecontaminated environments leading to important serviceability and safety reductions as well as increasing repair and maintenance costs (Bastidas-Arteaga and Schoefs 2012, 2015; Imam et al 2015; Kim et al 2016)
The heat transfer equations remain unchanged [Eqs. (11) and (12)] in the heat equations we have removed the heat flows from vapor diffusion and convection terms that are negligible as compared to the heat conduction (Samson and Marchand 2007)
Reduced model & dt = 7days differences are superior to 4 mol/m3 concrete and increase with time. These results indicate that for this kind of exposure and climate the assessment of chlorideinduced corrosion risks is very sensitive to the choice of the climate model as well as the training period for the daily monthly-based models (DMT)
Summary
2014; Radlinska et al 2014). Concrete provides physical and chemical protection to the reinforcing steel in these environments where the chloride sources are external (seawater, de-icing salts, and salt spray) or internal (chlorides from concrete mixing). In a recent research, de Vera et al (2015) used the Fick’s second law of diffusion to model chloride ingress into concrete structures exposed to atmospheric environment assuming that the chloride flux is constant Under this assumption it is possible to consider a time-variant surface chloride concentration. The advantage of analytical solutions of Fick’s law is their low computational cost; these models cannot represent accurately chloride ingress under real (complex) exposure conditions, leading to poor prediction This point is improved by Nernst–Planck based models but they are generally computationally expensive (Marchand and Samson 2009). Time-averaged exposure data neglects important climate variations leading to the reduction of chloride ingress penetration rates (Flint et al 2014); understanding the influence of these aspects becomes essential to improve the accuracy of chloride ingress modeling Within this context, the purposes of this study are:.
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