Modeling the Structural Effects of Rust in Concrete Cover

Abstract

Vast governmental budgets are spent annually to face corrosion problems of steel reinforcement in concrete bridges attributable to the extensive use of deicing salts. Corrosion controls the lifetime of a bridge, which has two distinct periods. During the first period, chlorides diffuse through the cover. When sufficient chlorides are formed at the rebars, corrosion initiates. This marks the start of the second period, during which rust with higher volume to bare steel is produced. The rust puts pressure on the cover, which finally leads to cover spalling. In this paper, a model is developed to determine the time span of the second period. The model includes a volume compatibility condition that allows for the proper introduction of compaction of all materials that contribute to cover spalling, including the rust. A new condition for marking failure of the cover is also established, based on fracture mechanics and strain energies. Finally, a new formula is proposed for the rate of rust production, which allows for the constant rust production at early and nonlinear diffusion dependant rates at latter stages of corrosion.

A double-cylinder model incorporating confinement effects for the analysis of corrosion-caused cover cracking in reinforced concrete structures

“…Bhargava et al [2,[10][11][12] postulated that the concrete in the cracked cylinder was an isotropic linear elastic material with a reduced elastic modulus compared to that of the outer uncracked concrete cylinder. Balafas and Burgoyne [13] proposed a double-cylinder model based on the fracture mechanics theory to determine structural lifetime from corrosion initiation to cover spalling. Li et al [14][15] assumed that the cracked concrete cylinder was an isotropic material with a reduced elastic modulus in the tangential direction.…”

Analytical Model for Residual Bond Strength of Corroded Reinforcement in Concrete Structures

“…However, as pitting corrosion progresses, it appears as uniform corrosion in the later stage, as demonstrated in the long-term natural corrosion experimental studies by Zhang et al (2010). The assumption for uniform expansive pressure at the bond interface is reasonable, as shown in many studies such as Balafas andBurgoyne (2011), Bhargava et al (2008), Chen and Xiao (2012), Chernin et al (2010) and Zhong et al (2010).…”

Predicción de la vida útil en servicio de edificios de 50 años expuestos a ambientes marinos

“…The uncracked part of the cover is treated as a thick-walled cylinder and the front of the crack (R c ) is ruled by the cubic Eq. (3) (Balafas and Burgoyne, 2011):…”

“…Figure 11 shows the variation in the corrosion current density (i corr ) versus time. The ability to predict the time to cover cracking is important marks the end of the structure's fully effective service life (Balafas and Burgoyne, 2011).…”

“…Service life prediction for 50-year-old buildings in marine environments • 7 software and following the modelling detailed by (Balafas and Burgoyne, 2011 These i corr values were used in order to cover a wide steel corrosion rate range, more than that experimentally measured: 0.34-0.69 mA·cm −2 in the rust or 0.11-0.23 mA·cm −2 in the steel, in the buildings located in marine environments indicated above. The input parameters of the steel, concrete and rust properties used in the numerical simulation are included in Table 4.…”