The Corrosion of Steel Reinforcement in Carbonated Concrete Under Different Humidity Regimes

1994 ◽  
Vol 370 ◽  
Author(s):  
Anastasia G. Constantinou ◽  
Karen L. Scrivener
Keyword(s):  
Corrosion Rate ◽  
Concrete Cover ◽  
Interfacial Region ◽  
Reinforcing Bars ◽  
Electrochemical Monitoring ◽  
Corrosion Of Steel ◽  
Curing Regimes ◽  
Linear Polarisation ◽  
Concrete Interface ◽  
Microstructural Examination

AbstractIn this investigation, four concretes (two mix designs and two curing regimes), containing reinforcing bars at covers 11 mm and 20 mm were carbonated fully in 100% CO2 and 65% relative humidity (RH). They were then placed in two different humidity environments (65% RH and 90% RH). The progress of the corrosion of the samples was followed electrochemically (using the linear polarisation technique) and microscopically (using a scanning electron microscope).Electrochemical monitoring of the corrosion rate showed that corrosion started very soon after placement in the humidity regimes and generally increased with time. The water/cement ratio, the concrete cover of the reinforcement and the curing of the concrete had a significant effect the length of time taken to carbonate the specimens. However, the effect of these variables on the corrosion rate was negligible. In addition, the corrosion rate showed no dependance on the humidity regimes.Microstructural examination of the samples revealed the existence of corrosion products at the steel/concrete interface after 6 months in the humidity regimes. There was more corrosion product in the samples at 90% RH. The samples with the low w/c showed more extensive cracking in the interfacial region.

scholarly journals Corrosion of steel in concrete due to one and two dimensional chloride ingress

2018 ◽  
Vol 199 ◽  
pp. 04004
Author(s):  
Ze Gyang Zakka ◽  
Mike Otieno
Keyword(s):  
Corrosion Rate ◽  
Concrete Beams ◽  
Concrete Cover ◽  
Steel Reinforcement ◽  
Chloride Ingress ◽  
Single Crack ◽  
Ongoing Research ◽  
Concrete Resistivity ◽  
Corrosion Of Steel ◽  
Cracked Specimens

This paper presents results of an ongoing research of the effect of 1D and 2D chloride ingress on concrete resistivity and corrosion rate of steel reinforcement. 12 concrete beams made with concrete of binder blend PC(50)/GGBS(50), w/b = 0.40, 10 mm steel reinforcement rods at concrete cover of 20 mm were used in this laboratory based experiment. The steel reinforcement bars were placed at the middle or at an orthogonal corner of the concrete beams subjected to 1D and 2D chloride ingress respectively. A single crack was induced using 3-point bending on one-half of the beams. The beams were exposed to a repeated cycle of 2 weeks ponding in 5% NaCl and then air drying in ambient laboratory condition for 2 weeks. The corrosion rate of both cracked and uncracked specimens exposed to 2D chloride ingress was significantly higher than that of beams exposed to 1D chloride ingress. The uncracked specimens had lower concrete resistivity values compared to the cracked specimens even though higher corrosion rates were measured.

Microstructure Analysis of the Rust Developing at Steel-Concrete Interface

2008 ◽  
Vol 400-402 ◽  
pp. 215-220
Author(s):  
Rong Zhen Dong ◽  
Jun Wei ◽  
Xi Wu Zhou
Keyword(s):  
Iron Oxidation ◽  
Concrete Cover ◽  
Forming Process ◽  
Final State ◽  
Steel Bar ◽  
Galvanostatic Method ◽  
Hematite Fe2o3 ◽  
Distribution Composition ◽  
Corrosion Of Steel ◽  
Concrete Interface

The rust distribution and the crack expansion in the deteriorated concrete were studied through the macroscopic and microcosmic method. The results show that the corrosion of steel bar in the concrete is non-uniform even though by Galvanostatic Method. The crack appears earlier and expands quicker at the thin concrete cover than others side and the short crack filled by the rust is found near by the steel bar and converges the main crack. The distribution, composition and the developing of the rust at steel-concrete interface were studied by the microscopic methods of BSE, EDAX and Raman Microscope. By these methods, the rust distributes inhomogeneous and the ion element area was divided into zones evidently. From concrete to steel bar, the rust in turn is: initial rust zone, the mixture area of the rust and mortar about 20-50 μm in width and main containing the goethite (FeOOH); the secondary rust zone, high density area of ion element and about 10-20μm in width and being the mixture of hematite（Fe2O3）and magnetite(Fe3O4); the final rust zone, similar as the initial rust and being the mixture of hematite(Fe2O3)and goethite(FeOOH). According to the electrochemistry principle, the forming process of rust does not follow the iron oxidation procedure entirely but form middle production under the special situation of the condition interior concrete and the electric field outside. The extrusion action of concrete around steel bar makes the rust compressed and metamorphic and the secondary rust forming. So the process and the final state of this special corrosion production are the key parameters leading to the deterioration of concrete.

Effect of Steel-Concrete Interface on Reinforcement Corrosion in Marine Environment

2011 ◽  
Vol 250-253 ◽  
pp. 1311-1314
Author(s):  
Rui Jin Zhang
Keyword(s):  
Corrosion Rate ◽  
Environmental Conditions ◽  
Concrete Cover ◽  
Reinforcement Corrosion ◽  
Interface Quality ◽  
Corrosion Initiation ◽  
Concrete Members ◽  
Chloride Threshold ◽  
Interface Defects ◽  
Concrete Interface

This paper dealt with the influence of the steel-concrete interface quality and environmental conditions on reinforcement corrosion. High size concrete members were cast to get different interface quality decreased with the height of rebar due to the top-bar effect. Five groups of specimen with two concrete covers have subjected to different exposed programs. The experimental results showed that the concrete cover significantly influenced corrosion initiation and corrosion rate by blocking the penetration of aggressive agents. The height of rebar affected the corrosion initiation because of the variation of concrete porosity, interface defects and chloride threshold. The existence of defects at the interface was more important than the size of defect for corrosion initiation.

scholarly journals Corrosion of Steel Rebars in Anoxic Environments. Part I: Electrochemical Measurements

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2491
Author(s):  
Elena Garcia ◽  
Julio Torres ◽  
Nuria Rebolledo ◽  
Raul Arrabal ◽  
Javier Sanchez
Keyword(s):  
Corrosion Rate ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Chloride Content ◽  
Offshore Platforms ◽  
Anoxic Conditions ◽  
Current Limit ◽  
Anoxic Environments ◽  
Corrosion Of Steel ◽  
Steel Rebars

The number of reinforced concrete structures subject to anoxic conditions such as offshore platforms and geological storage facilities is growing steadily. This study explored the behaviour of embedded steel reinforcement corrosion under anoxic conditions in the presence of different chloride concentrations. Corrosion rate values were obtained by three electrochemical techniques: Linear polarization resistance, electrochemical impedance spectroscopy, and chronopotenciometry. The corrosion rate ceiling observed was 0.98 µA/cm2, irrespective of the chloride content in the concrete. By means of an Evans diagram, it was possible to estimate the value of the cathodic Tafel constant (bc) to be 180 mV dec−1, and the current limit yielded an ilim value of 0.98 µA/cm2. On the other hand, the corrosion potential would lie most likely in the −900 mVAg/AgCl to −1000 mVAg/AgCl range, whilst the bounds for the most probable corrosion rate were 0.61 µA/cm2 to 0.22 µA/cm2. The experiments conducted revealed clear evidence of corrosion-induced pitting that will be assessed in subsequent research.

Thermal effect on fiber reinforced polymer reinforced concrete slabs

2008 ◽  
Vol 35 (3) ◽  
pp. 312-320 ◽  
Author(s):  
A. Zaidi ◽  
R. Masmoudi
Keyword(s):  
Thermal Effect ◽  
Concrete Cover ◽  
Fiber Reinforced Polymer ◽  
Concrete Slabs ◽  
Fiber Reinforced ◽  
Reinforced Concrete Slabs ◽  
Reinforced Polymer ◽  
Frp Bar ◽  
Frp Bars ◽  
Concrete Interface

The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar – concrete interface, which induces tensile stresses within the concrete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insufficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from –30 to +80 °C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 °C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 °C. Also, the first cracks appear in concrete at the FRP bar – concrete interface at temperatures around +40 °C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.

Test and Study on Impact of Corrosion on Bond Force between Steel and Concrete

2010 ◽  
Vol 36 ◽  
pp. 176-181
Author(s):  
Xian Feng He ◽  
Shou Gang Zhao ◽  
Yuan Bao Leng
Keyword(s):  
Reinforced Concrete ◽  
Corrosion Rate ◽  
Concrete Structure ◽  
Steel Corrosion ◽  
Reinforced Concrete Structure ◽  
Bond Force ◽  
Steel Bars ◽  
Protection Layer ◽  
Corrosion Of Steel ◽  
The Impact

The corrosion of steel will have a bad impact on the safety of reinforced concrete structure. In severe cases, it may even be disastrous. In order to understand the impact of steel corrosion on the structure, tests are carried out to study corrosion and expansion rules of steel bars as well as the impact rules of corrosion on bond force between steel and concrete. The results show that wet and salty environment will result in steel corrosion; relatively minor corrosion will not cause expansion cracks of protection layers; when steel rust to a certain extent, it will cause cracks along the protection layer; when there exists minor corrosion in steel and the protection layer does not have expansion cracks, the bond force is still large and rapidly decreases as the corrosion rate increases.

scholarly journals Effect Use of Two Chemical Compounds Sodium Nitrate and Sodium Silicate as Corrosion Inhibitor to Steel Reinforcement

2019 ◽  
Vol 14 (2) ◽  
pp. 123-128
Author(s):  
Sarah Kareem Mohammed
Keyword(s):  
Corrosion Rate ◽  
Sodium Silicate ◽  
Electrolyte Solution ◽  
Sodium Nitrite ◽  
Corrosion Inhibitors ◽  
Sea Water ◽  
Chemical Compounds ◽  
Steel Sample ◽  
Steel Reinforcement ◽  
Corrosion Of Steel

Corrosion of steel reinforcement is one of the biggest problems facing all countries in the world like bridges in the beach area and marine constructions which lead to study these problems and apply some economical solutions. According to the high cost of repair for these constructions, were studied the effect of using kind of chemical compounds sodium nitrite(NaNO2) and sodium silicate(Na2SiO3) as corrosion inhibitors admixture for steel bars that immersed partially in electrolyte solution (water + sodium chloride in 3% conc.) (Approximately similar to the concentration of salt in sea water). The two inhibitors above added each one to the electrolyte solution at concentrations (0.5%, 1% and 2%) for both of them.      The results were  corrosion rate for steel sample that's immersed partially in salt solution was higher than corrosion rate of steel bar that's immersed partially in electrolyte solution with inhibitors  also the two corrosion inhibitors (sodium nitrite and sodium silicate) that added to the electrolyte solution were working successfully to prevent and inhibit the corrosion by using weight loss technique with best percent of 0.5% sodium nitrite ( efficiency 94.1% ) and best percent of 2% sodium silicate ( efficiency 92.5%).

Determination of Cl- in Concrete Materials by Ion Chromatography

2016 ◽  
Vol 680 ◽  
pp. 52-55
Author(s):  
Hong Yan Guan ◽  
Jian Jun Ding ◽  
Zhong Bao Guo ◽  
Ming Yu Wang ◽  
Yi Fei Mei
Keyword(s):  
Detection Limit ◽  
Ion Chromatography ◽  
Potential Method ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Accurate Analysis ◽  
Chromatography Method ◽  
Concrete Materials ◽  
Corrosion Of Steel

The determination of chloride ions in concrete materials accurately is far and away crucial, since chloride ions can cause corrosion of steel and concrete cover off. The conventional potential method and silver nitrate titration method usually show features of simple operation and short duration, nevertheless, they are not suitable for accurate analysis for concrete attributing to their low accuracy and detection limit. In this paper, an ion chromatography method was presented to determine chlorine in concrete materials. Concrete samples were pre-processed and then extracted with distilled water. The extraction solutions were purified on a 0.22 μm filter membrane, an On Guard SPE-RP column and a SPE-H column sequentially for eliminating undissolved substance, organisms and metal ions before ion chromatographic analysis. The chromatographic separation was performed on a Dionex ICS-1000 Chromatographic using 25.0 mmol/L KOH solutions as mobile phase at 1.0 mL/min. Results show that the detection limit of the method was 0.004 mg/L. The linear relationship of the external Cl- standard solutions was 0.9994, and the sample analytical RSD was 0.44%.

Which Rust Deposition Model Should Be Used in Predicting Concrete Cover Cracking due to Reinforcement Corrosion?

2012 ◽  
Vol 468-471 ◽  
pp. 1000-1004 ◽  
Author(s):  
Roger Zou ◽  
Frank Collins
Keyword(s):  
Predictive Model ◽  
Concrete Cover ◽  
Zone Model ◽  
Reinforcement Corrosion ◽  
Rust Layer ◽  
Rc Structures ◽  
Cover Cracking ◽  
Porous Zone ◽  
Walled Cylinder ◽  
Concrete Interface

The critical amount of corroded steel that causes concrete cover cracking can be readily calculated based on thick-walled cylinder theory. However, the results may vary significantly depending on how the rust deposition is considered. There are several rust deposition hypothesis proposed in the literature for modelling concrete cover cracking of RC structures due to reinforcement corrosion. Among them, three are considered representative ones and have been widely cited in the literature. They are: (i) assumes a certain amount of rust product carried away from the rust layer and deposited within the open cracks proposed by Pantazopoulou and Papoulia; (ii) assumes all of the rust products build up around the bar and all of them are responsible for the expansive pressure proposed by Bazant; (iii) assumes certain amount of rust products deposited into a porous zone around the bar/concrete interface proposed by Liu and Weyers. In this paper, all three rust deposition hypotheses were examined for the critical amount of corrosion to induce cover cracking. When compared to the test data available from the literature, it showed that the porous zone model proposed by Liu and Weyers gives the best predictions. Thus it may be concluded that assuming a porous zone around the steel/concrete interface would be reasonable and may be adopted in developing concrete cover cracking predictive model.

An Instrumented Field Corrosion Test Loop

1998 ◽  
Author(s):  
Alebachew Demoz ◽  
Kirk H. Michaelian ◽  
John Donini ◽  
Sankara Papavinasam ◽  
R. Winston Revie
Keyword(s):  
Weight Loss ◽  
Corrosion Rate ◽  
Corrosion Test ◽  
Visual Inspection ◽  
Electrochemical Methods ◽  
Corrosion Rates ◽  
Test Loop ◽  
The Media ◽  
Electrochemical Monitoring ◽  
Multi Phase

A multi-purpose instrumented loop in line with an oil producing well is described. The loop has several ports for coupons which were replaced periodically. Some of the coupons were used for electrochemical monitoring in addition to weight loss and visual inspection. Weight loss, pit rate and all the electrochemical methods used gave corrosion rates that were dependent on the positions of the coupons inside the loop. The corrosion rate of the coupons increased from top to bottom. This order reflected the media and flow to which the coupons were exposed in a multi-phase producing well.

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