Reinforcement Corrosion in Concrete

In many cases, any attack on reinforced concrete will be on the concrete itself. However, there are two species, namely, chloride and carbon dioxide that penetrate the concrete and attack the reinforcing steel without breaking the concrete. The chloride and carbon dioxide penetrate concrete without causing significant damage and then promote corrosion of the steel by attaeking and removing the protective passive oxide layer on the steel created and sustained by the alkalinity of the concrete pore water. 

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Broomfield, J., Davies, K., Hladky, K. and Noyce, P. (2003). Monitoring of Reinforcement Corrosion in Concrete Structures in the Field. Concrete Solutions, 1st Intern. Conference on Concrete Repari St.-Malo, France, Proceedings. M. Grantham, F. Rendell, R. Jauberthie and C. Lanos (eds). Publ Concrete Solutions (on CD Rom). 

Fig. 6.83 Effect of chloride ions on the reinforcement corrosion in concrete. (According to [343])...

Chlorides concentration of 0.6% by mass of concrete is reducing the resistivity two times [60], Therefore, the progress of reinforcement corrosion in concrete can be assessed from measurements of surface resistivity [60],... 

Despite the impressive progress made in controlling the corrosion of steel in concrete in the last thirty years, reinforcement corrosion in concrete structures is still a challenging problem. Important methods to mitigate reinforcement corrosion are described below. 

A similar danger of corrosion lies in cell formation in steel-concrete foundations (see Section 4.3). Such steel-concrete cells are today the most frequent cause of the increasing amount of premature damage at defects in the coating of new steel pipelines. The incidence of this type of cell formation is increased by the connection of potential-equalizing conductors in internal gas pipelines and domestic water pipelines [25], as well as by the increased use of reinforcing steel in concrete foundations for grounding electrical installations [26]. 

Corrosion usually results in a leak or failure of a support because a vessel or support gets too thin. It is then not strong enough to withstand the pressure or load. However, rust can cause failure in another way. It occupies about seven times the volume of the steel from which it was formed. V/hen rust occurs between two plates that have been bolted or riveted together, a high pressure develops. This can force the plates apart or even break the bolts or rivets (see Section 9.1.2 g). Corrosion of the reinforcement bars in concrete can cause the concrete to crack and break away. 

Test method for porosity in gold platings on metal substrates by gas exposures Test method for half-cell potentials of uncoated reinforcing steel in concrete Method for detection of copper corrosion from petroleum products by the copper strip tarnish test... 

The protection of steel reinforcements. Concrete produces a layer of passivity at the steel/concrete interface and any breakdown of this can increase the chance of reinforcement corrosion. In addition, it is important that concrete be maintained in a state of low permeability to minimize the passage of moisture and air to the steel. 

Virmani, Y.P., Clear, K.C. and Pasko, T.J. (1983). Time to Corrosion of Reinforced Steel in Concrete Slabs, Vol. 5, Calcium Nitrite Admixtures or Epoxy Coated Reinforced Bars as Corrosion Protective Systems, FHWA-RD-83-012, FHWA, US Department of Transportation, 71. 

Steel reinforcement rods in concrete are only practicable when the iron is deeply embedded in the concrete and therefore protected for decades against corrosion by the very durable alkaline environment of the concrete, since concrete is only slowly carbonated by the carbon dioxide (CO2) in the environment, resulting in a neutralization of its pH value. The reinforcement rods in the ceiling of the morgue in question lie directly on the surface, where the pH value would fall very quickly (i.e., would become less alkaline), particularly when rain water containing CO2 penetrated the concrete see the crack in Fig. 25 which would quickly allow the entry of rain water. 

Corrosion Evaluation of Epoxy-coated Metallic-clad and Solid Metallic Reinforcing Bars in Concrete, US Department of Transportation, Federal Highway Administration, Publication FHWA-RD-98-153, December 1998. 

NACE Standard RP 0187, Design considerations for corrosion control of reinforcing steel in concrete, NACE Int., Houston, Texas, 2000. 

Corrosion of reinforcing steel in concrete (elevated highway. Providence, RI), where road de-icing salts combine with acid precipitation to produce a severe environment. (Photo by Robert Baboian.)... 

The extent of aqueous corrosion often depends on the presence of impurities and trace contaminants in the water present. For example, carbon-steel reinforcing bars in concrete corrode more severely in acidic conditions and in the presence of chloride ions, a process called electrochemical attack. On the... 

A. Mazzoni, E. Nolan, H. Wojtas, Reinforcement corrosion and concrete resistivity - State of the art, laboratory and field results , Proc. Int. Conf. on Corrosion and Corrosion Protection of Steel in Concrete,... 

T. K. H. Al-Kadhimi, P. Banfill, S.G. Millard, ). H. Bungey, An accelerated carbonation procedure for studies on concrete , Advances in Cement Research, 1996, 8 (30), 47-59. C. L. Page, Nature and properties of concrete in relation to reinforcement corrosion , in Corrosion of Steel in Concrete, Aachen, 17-19 February 1992. 

W. H. Hartt, A. M. Rosenberg, Influence of Ca(N02)2 on Seawater Corrosion of Reinforcing Steel in Concrete , American Concrete Institute, Detroit, SP 65-33, 609-622, 1989. 

Very high corrosion rates in the vicinity of defects in the coating can occur in the presence of macrocells. A typical situation is that of stractures in which epoxy-coated reinforcement in contact with chloride-contaminated concrete is coupled to non-coated reinforcement embedded in concrete that is uncontaminated or contains a level of chlorides below the critical level. In this case, the passive non-coated... 

U. Niirnberger, W. Beul, G. Onuseit, Corrosion behaviour of welded stainless reinforcing steel in concrete , Otto Graf Journal, 1993, 4,... 

J- Hewitt, M. Tullmin, Corrosion and stress-corrosion cracking performance of stainless steel and other reinforcing materials in concrete , in Corrosion and Corrosion Protection of Steel in Concrete, R. N. Swamy (Ed.), Vol, I, 1994, 527-539. 

J. E. Bennet, T. A. Mitchell, Depolarization testing of cathodi-cally protected reinforcing steel in concrete . Corrosion 89, Nace, Paper 373, 1989. 

Salt-induced reinforcing steel corrosion in concrete bridges is a serious problem and an economic burden. Although the positive effect of corrosion protection measures can be seen on individual cases, there are many bridges (thousands) without corrosion control. 

F. Mansfeld, M.W. Kendig, S. Tsai, Application of acoustic emission to detection of reinforcing steel corrosion in concrete. Corrosion 38 (1982) 9-14. 

Rebar corrosion in concrete is considered to occur in two phases [8]. The first phase begins with construction of the structure and ends with corrosion initiation when depassivating species reach the reinforcement. The second phase is the active corrosion that destroys the structure. Controlling rebar corrosion in this phase is very difficult. Passive film corrosion is initiated when local pore solution at the concrete-rebar interface drops below the passivation pH due to the presence of atmospheric carbon dioxide (carbonation) or chloride penetration. The following mechanism controls the carbonation process ... 

ASTM C876-09, Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete, ASTM International, Philadelphia, PA, 2009. 

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