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Rebar corrosion

Carbonation (Chapter 5) or ingress of chloride ions (Chapter 6) are the two principal causes of rebar corrosion. Inspection, condition assessment and prediction of the future service life of a structure require information on the carbonation depth or chloride content of concrete. The areas on a structure where these chemical analyses are performed should be based on a problem-oriented approach, e. g. on visual inspection or better on potential mapping. [Pg.291]

C. Andrade, ). Sarria, C. Alonso, Statistical study on simultaneous monitoring of rebar corrosion rate and internal RH in concrete structures exposed to the atmosphere , in Corrosion of Reinforcement in Concrete Construction, C. L. Page,... [Pg.295]

To this concern. Figure 20.5 shows the results of application of cathodic prevention to slabs subjected to ponding with a NaCl solution [43]. After about 700 days, initiation of rebar corrosion was detected in the control slab (in the free corrosion condition) at spots where the chloride content at the steel surface had reached more than about 1 % by mass of cement. From about that point in time, the slab receiving a very low current density of 0.4 mA/m showed a similar (instant-off) potential as the control slab and its 4-hour decay values became lower than 100 mV. The slab receiving 0.8 mA/m showed lower decays from about... [Pg.356]

C. Andrade, M. Castellote, ]. Sarria, C. Alonso, Evolution of pore solution chemistry, electro-osmosis and rebar corrosion rate induced by realkalisation . Materials and Structures, 1999, 32, 427-436. [Pg.380]

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 ... [Pg.529]

Once Ca(OH)2 is neutrafized with carbonic acid, pH falls to 8. At this pH, rebar corrosion is activated with porous rust formation that causes internal expansion, damaging and eventually causing spalling. [Pg.529]

Model simulations for Myrtle Beach Bridge SimCorr was used to predict rebar corrosion behavior in the Myrtle Beach Bridge in South Carolina. Myrtle Beach Bridge is a coastal bridge and chloride is present at aU times and exposure risk to chloride is considered severe. Surface chloride concentration of 7.36 kg/ta was used in aU simulations. Table 12.2 summarizes the conditions used. Figures 12.16 and 12.17 show the chloride concentration profiles for cases 1 and 2 outlined in Table 12.2 for 7.36 kg/m surface chloride concentration. With an inhibitor, the time required to exceed the chloride concentration threshold value increases even under severe ... [Pg.549]

S. Guzman, J.C. Galvez, J.M. Sancho, Cover cracking of reinforced concrete due to rebar corrosion induced by chloride penetration, Cem. Concr. Res. 41 (2011) 893—902. [Pg.555]

Andrade, C., Alonso, C., Feliu, S. and Gonzalez, J.A. (1995). Progress on Design and Residual Life Calculation with Regard to Rebar Corrosion on Reinforced Concrete, in Techniques to Assess the Corrosion Activity of Steel Reinforced Concrete Structures, ASTM STP 1276, N.S. Berke, E. Escalante, C.K. Nmai and D. Whiting (eds), American Society of Testing and Materials, West Conshohocken, PA. [Pg.98]

In steel-reinforced constmctions the chloride ions present in seawater migrate towards the reinforcement, and may cause its corrosion. Rebar corrosion develops most rapidly in the splash zone, owing to a sufficient oxygen supply, high chloride penetration, and the presence of appropriate amounts of water (Sakoda et al, 1992). [Pg.294]

Clemena, G., Jackson, D., md Crawford, G., Inclusion of Rebar Corrosion Rate Measurements in Condition Surveys of Concrete Bridge Decks, Trtmsportation Research Board, Paper 920344, Washington, DC, January 1992. [Pg.411]

Powder coatings 18 Automotive parts, engine blocks, construction panels, radiators, tools, steel furniture, pipes, valves and fittings, concrete reinforcing rebar, corrosion protection of steel pipes and fittings used in the oil and gas industry, potable water transmission pipelines... [Pg.256]

This chapter reviews the chemistries, properties, and commercial uses water-containing ionicaUy conductive polymer systems. In medical applications, these polymers serve as the conductive interface between the patient s skin and the medical equipment. These electrolyte systems are commercially produced in gel, paste, or sheet form using either natural or synthetic polymers. Regardless of the physical form, these systems are typically formulated to a conductivity range of 10 to 10 S cm to provide acceptable performance. A new plication of this type of polymer is reported recently in the prevention of steel rebar corrosion in concrete structures. [Pg.293]

A serious problem which is faced by building industry is rebar corrosion in concrete. In steel reinforced concrete structure, corrosion attack is prevented by high alkaline environment in... [Pg.373]

Which one of the following inhibitors is considered effective for inhibition of rebar corrosion ... [Pg.379]

The importance of concrete cracks in rebar corrosion has also been highlighted by Niirnberger. Both carbonation and chloride ion diffusion, two important processes associated with rebar corrosion, can proceed more rapidly into the concrete along the crack faces, compared with uncracked concrete. Niirnberger argued that corrosion in the vicinity of the crack tip could be accelerated further by crevice corrosion effects and galvanic cell formation. The steel in the crack will tend to be anodic relative to the cathodic (passive) zones in uncracked... [Pg.157]

Figure 2.26 Relative volume of possible rebar corrosion products. Figure 2.26 Relative volume of possible rebar corrosion products.
Chloride-induced rebar corrosion. Corrosion damage to reinforcing steel is an electrochemical process with anodic and cathodic half-cell reactions. In the absence of chloride ions, the anodic dissolution reaction of iron. [Pg.159]

Figure 2.27 Concrete degradation caused by rebar corrosion damage in a highway structure in downtown Toronto, Ontario. Extensive repair work was underway on this structure at the time the picture was taken. The annual maintenance costs for this structure were recently reported at around 18 million. Figure 2.27 Concrete degradation caused by rebar corrosion damage in a highway structure in downtown Toronto, Ontario. Extensive repair work was underway on this structure at the time the picture was taken. The annual maintenance costs for this structure were recently reported at around 18 million.
Figure 2.28 Concrete degradation caused by rebar corrosion damage near Kingston, Ontario. This bridge underwent extensive rehabilitation shortly after this picture was taken. Figure 2.28 Concrete degradation caused by rebar corrosion damage near Kingston, Ontario. This bridge underwent extensive rehabilitation shortly after this picture was taken.
Chloride-induced rebar corrosion tends to be a localized corrosion process, with the original passive surface being destroyed locally under the influence of chloride ions. Apart from the internal stresses created by the formation of corrosion products leading to cracking and spalling of the concrete cover, chloride attack ultimately reduces the cross section and significantly compromises the load-carrying capability of steel-reinforced concrete. [Pg.163]

Sources of chloride ions and diffusion into concrete. The harmful chloride ions leading to rebar corrosion damage either originate directly from the concrete mix constituents or diffuse into the concrete from the surrounding environment. The use of seawater or aggregate that has been exposed to saline water (such as beach sand) in concrete mixes creates the former case. Calcium chloride has been deliberately added to certain concrete mixes to accelerate hardening at low temperatures, mainly before the harmful corrosion effects were widely known. [Pg.163]

The determination of a critical chloride level, below which serious rebar corrosion damage does not occur, for design, maintenance planning, and life prediction purposes is appealing. Not surprisingly, then, several studies have been directed at defining such a parameter. Unfortunately, the concept of a critical chloride content as a universal parameter is unrealistic. Rather, a critical chloride level should be defined only in combination with a host of other parameters. After all, a threshold chloride level for corrosion damage will be influenced by variables such as... [Pg.164]

One of the better-known corrosion-inhibitor admixtures used in attempting to control chloride-induced rebar corrosion is calcium nitrite, Ca(N02)2. The mechanism of inhibition involves nitrite ions competing with chloride ions to react with Fe + ions produced at the anode. Essentially, the nitrite ions hmit the formation of unstable iron chloride complexes and promote the formation of stable compounds that passivate the rebar surface. The following reactions have been proposed ... [Pg.178]

An important consideration for any corrosion-inhibiting admixture is its effects on the properties of concrete, such as workability, curing time, and strength. Many mechanistic details of commercial rebar corrosion inhibitors have remained relatively obscure because of the proprietary nature of their formulations. [Pg.178]

Probabihty of active rebar corrosion ASTM C 876 based on corrosion potential (note that no corrosion rate is determined)... [Pg.181]


See other pages where Rebar corrosion is mentioned: [Pg.321]    [Pg.227]    [Pg.132]    [Pg.536]    [Pg.540]    [Pg.73]    [Pg.18]    [Pg.269]    [Pg.95]    [Pg.406]    [Pg.944]    [Pg.987]    [Pg.616]    [Pg.660]    [Pg.57]    [Pg.155]    [Pg.155]    [Pg.157]    [Pg.166]    [Pg.166]    [Pg.174]    [Pg.180]    [Pg.184]   
See also in sourсe #XX -- [ Pg.373 , Pg.617 ]




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