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

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 threedimensional 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 uncracked 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 in Croatia 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.

Assessment of Performance Indicators of a Large-Span Reinforced Concrete Arch Bridge in a Multi-Hazard Environment

“…The 3D CHTM model is more comprehensive and describes chloride transport in concrete as diffusion, convection, and physical and chemical binding by cement paste. The model is simulated in a 3D domain and uncracked and cracked concrete are considered, while the diffusion coefficient depends on the concrete mixture and is a function of the crack width [13,14,42].…”

“…On the other hand, bridges with large spans or structures of high strategic importance usually have a longer service life and an extended assessment that includes not only a visual inspection but also several in-situ and laboratory tests, structural health monitoring, and optionally, a numerical analysis of the structural assessment, remaining service life and life cycle cost [1]. However, most of the published research papers address only one or a few aspects: e.g., structural assessment of bearing capacity in the combination of numerical analysis and experimental testing [4,5], experimental testing of a specific structural element or detail [6][7][8][9], evaluation and effectiveness of non-destructive testing [3,9,10], analytic models on failure modes [11], and numerical and experimental analysis of the main degradation mechanisms [12][13][14]. A comprehensive assessment of road bridges is included in [1], but in this case, the assessment is based on visual inspection and standard bridges of small and medium spans are analyzed.…”

Numerical modeling of the behavior of concrete exposed to chloride ions by coupling age and mechanical stresses

“…Reinforced concrete structures are engineered for long-term durability [1], but they gradually deteriorate due to corrosion induced by the harsh environmental conditions they encounter [2], [3]. The steel, which is initially shielded by the concrete coating, can lose its protective properties due to either carbonation caused by carbon dioxide or the infiltration of chloride ions from seawater, sea spray, or de-icing salts [4]. This phenomenon poses a greater risk when the structure is exposed to mechanical strain [5] and deteriorates progressively [6], [7].…”

Portable Measurement Systems Based on Microcontrollers to Test Durability of Structures: Mini-Review

“…Some common ions speed up the corrosion in the RC structures. One of the most studied is the Chloride ion, the penetration in the concrete (Wang et al, 2018), how it interacts with cracked concrete (Kušter Marić et al, 2020), and how it is transported to the steel. These studies lead to models that can characterize how the transport changes depending on the wetting/drying cycles (van der Zanden et al, 2015;Kušter Marić et al, 2020).…”

“…One of the most studied is the Chloride ion, the penetration in the concrete (Wang et al, 2018), how it interacts with cracked concrete (Kušter Marić et al, 2020), and how it is transported to the steel. These studies lead to models that can characterize how the transport changes depending on the wetting/drying cycles (van der Zanden et al, 2015;Kušter Marić et al, 2020). In this mini-review, standard corrosion detection methods are presented, including commercial devices used; the third section shows recent developments in terms of low-cost and portable devices that meet similar criteria, also embedded sensors, and a benchmark.…”