Chloride Transport in Cracked Concrete Subjected to Wetting – Drying Cycles: Numerical Simulations and Measurements on Bridges Exposed to De-Icing Salts

Marija Kušter Marić,Serena Gambarelli,Joško Ožbolt,Gojko Balabanić,Olesya Zhychkovska

doi:10.3389/fbuil.2020.561897

Abstract

Although many models for service life predictions have been developed, their application to existing bridges is still not at a satisfactory level. The here presented coupled 3D chemo-hygro-thermo mechanical (CHTM) model can realistically simulate both corrosion phases: initiation and propagation. The focus of this research is the transport processes in cracked and un-cracked concrete before reinforcement depassivation. Realistic environmental conditions with the surface water and chloride contents variable in time are simulated based on the meteorological data for a mountain region where case studies bridges are located. Application of the large quantities of de-icing salts in combination with the poorly designed and executed details resulted in a high chloride content in concrete of the superstructure of both bridges: at the reinforcement level chloride content in cracked concrete elements exceeds the threshold value up to 10 times. Numerical results match well with the chloride content measured on the bridges after 11 and 14 years of service. Accounting for the realistic environmental conditions (wetting-drying cycles, application of de-icing salts only in the winter season, etc.) in the numerical simulations results in the continuous transport processes in concrete and higher chloride content in deeper concrete layers as opposed to the finite element models with the constant boundary conditions.

Highlights

Failure or even collapse of a bridge causes high direct and indirect costs, but sometimes, human lives
Because in the previous chapter the numerical simulations with included wetting–drying cycles have shown more realistic results, the models without wetting–drying cycles are not included in the following analysis
Several numerical models with the different crack widths ranging from cw = 0.00 to cw = 0.20 mm are considered

Summary

Introduction

Failure or even collapse of a bridge causes high direct and indirect costs, but sometimes, human lives. Besides assessment of the current conditions of the structures, in an efficient and effective bridge management system, it is important to predict their future deterioration and remaining service life using numerical models. Most bridges worldwide are made of concrete and exposed to de-icing salts and/or maritime environment. The main degradation process of those structures is chloride-induced corrosion of steel reinforcement in concrete. Once the threshold chloride content in concrete reaches the reinforcement level, reinforcement depassivation occurs, and electrochemical processes of active corrosion start. By including degradation models in probabilistic analysis of structure reliability, high level of uncertainties in knowledge on parameters and processes and their accumulation in complex degradation of structures such as chloride-induced reinforcement corrosion result in low reliability (e.g., high probability of depassivation; Zambon et al, 2019). To achieve real structure reliability, it is necessary to reduce uncertainties in material properties as well as in electrochemical and mechanical processes by application of more comprehensive models and their verification on existing structures

Methods

Results

Conclusion