Chloride threshold level for corrosion of steel in concrete

Conducting polymers are extensively studied due to their outstanding properties, including tunable electrical property, optical and high mechanical properties, easy synthesis and effortless fabrication and high environmental stability over conventional inorganic materials Although conducting polymers have a lot of limitations in their pristine form, hybridization with other materials overcomes these limitations The synergetic effects of conducting polymer composites give them wide applications in electrical, electronics and optoelectronic fields An in-depth analysis of composites of conducting polymers with carbonaceous materials, metal oxides, transition metals and transition metal dichalcogenides etc is used to study them effectively Here in this review we seek to describe the transport models which help to explain the conduction mechanism, relevant synthesis approaches, and physical properties, including electrical, optical and mechanical properties Recent developments in their applications in the fields of energy storage, photocatalysis, anti-corrosion coatings, biomedical applications and sensing applications are also explained Structural properties play an important role in the performance of the composites

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Conducting polymers: a comprehensive review on recent advances in synthesis, properties and applications

ii Acknowledgments iii List of Figures vii List of Tables x Notations xi 1.0 Introduction 1 1.1 Background 1 1.2 Deterioration Models 1 1.3 Scope of Study 3 2.0 Review of Corrosion of Steel in Concrete 2.1 Background 5 2.1.1 Mechanism of Electrochemical Corrosion 5 2.1.2 Pourbaix Diagrams 7 2.1.3 Polarization 8 2.1.4 Passivity 11 2.1.5 Growth of Rust Film 11 2.2 Corrosion of Steel in Concrete 12 2.2.1 Concrete as an Electrolyte 12 2.2.2 Principles of Steel Corrosion in Concrete 16 2.2.3 Initiation of Steel Corrosion in Concrete 19 2.2.4 Corrosive Activity of Concrete 21 2.3 Corrosion Monitoring Techniques 25 2.3.1 Half-cell Potential 25 2.3.2 Linear Polarization Technique 26 2.3.3 AC Impedance 28 2.3.4 Gravimetric Technique (Weight Loss Method) 28 2.3.5 Techniques for Determining the Chloride Content 29 2.4 Summary 29 3.0 Review of Time to Cracking Models 32 3.1 Cady-Weyers' Deterioration Model 32 3.2 Bazant’s Mathematical Models of Time to Cracking 32 3.3 Morinaga’s Empirical Equation of Time to Cracking 34 3.4 Other Metal Loss Criteria to Cracking 35 3.5 Some Comments on Existing Model s 36

Modeling the Time-to Corrosion Cracking of the Cover Concrete in Chloride Contaminated Reinforced Concrete Structures

Practical evaluation of relationship between concrete resistivity, water penetration, rapid chloride penetration and compressive strength

Degradation processes in reinforced concrete structures that affect durability are partially controlled by transport of aggressive ions through the concrete microstructure Ions are charged and the ability of concrete to hold out against transfer of ions greatly relies on its electrical resistivity Hence, a connection could be expected between electrical resistivity of concrete and the deterioration processes such as increase in permeability and corrosion of embedded steel Through this paper, an extensive literature review has been done to address relationship between concrete electrical resistivity and its certain durability characteristics These durability characteristics include chloride diffusivity and corrosion of reinforcement as these have major influence on concrete degradation process Overall, there exists an inverse or direct proportional correlation between these parameters Evaluated results, from measuring the concrete electrical resistivity, can also be used as a great indicator to identify early age characteristics of fresh concrete and for evaluation of its properties, determination of moisture content, connectivity of the micropores, and even condition assessment of in-service structures This paper also reviews and assesses research concerning the influential parameters such as environmental conditions and presence of steel rebar and cracks on measuring electrical resistivity of concrete Moreover, concrete resistivity concept, application, and its various measurement techniques are introduced

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Electrical Resistivity of Concrete for Durability Evaluation: A Review

It is common for the durability requirements of concrete structures built today to have a projected minimum service life of 75 years or more. In order to ensure that a new structure achieves this design life requires the use of high performance concretes made with the latest proven pozzolanic materials. Concrete chloride penetration resistance of concrete is among the most significant properties used to characterize high performance concretes today. To that effect diffusion tests are used, but because of their long duration, they do not lend themselves to measuring the chloride penetration properties of concrete during the course of construction. Surface Resistivity (SR) of water-saturated concrete at several different ages was studied and compared to the diffusion properties of the same concrete. A case is made to use SR as an electrical indicator of concrete chloride penetration resistance because of its strong correlation to diffusion tests, ease of implementation, non-destructive nature, and lower cost than any other test available.

Surface Resistivity as an Indicator of Concrete Chloride Penetration Resistance

The corrosion performance over a nearly 30-year service period of epoxy-coated rebar (ECR) in Florida marine bridges is presented. Severe ECR corrosion was noted earlier in several of those bridges, built with relatively high permeability concrete. Corrosion development took place later in some other structures with less permeable concrete, with instances where the corrosion was associated with preexisting cracks. Corrosion was found to be associated with coating imperfections and coating disbondment. Laboratory experiments and modeling indicated that macrocell coupling with remote cathodes was an aggravating factor. Quantitative damage functions relating the observed deterioration with service time of the affected bridges are presented. A predictive corrosion initiation-propagation model was developed and the model output is compared with the field results to identify suitable parameters for forecasting future rehabilitation needs. The prognosis for future corrosion development is discussed, wit...

Corrosion of Epoxy-Coated Rebar in Marine Bridges—Part 1: A 30-Year Perspective

Posttensioned concrete cylinder piles produced using a centrifugally cast, vibrated, roller-compacted process have shown promising corrosion resistance in marine environments. Three bridges in the Florida panhandle with ∼40 years in aggressive marine service and one newly constructed marine bridge utilizing concrete cylinder piles were examined. The older marine bridges showed minimal corrosion distress despite a low design concrete cover over the steel hoop reinforcement (2 cm to 4 cm). Typical concrete distress included minor rust staining (not necessarily indicating corrosion of reinforcement steel) and thin longitudinal cracks (likely caused by mechanical damage from pile driving). Chloride ion diffusivity was low, in the order of 1 × 10−9 cm2/s. Other measured parameters such as concrete resistivity, porosity, and water absorption indicate low permeability. Chloride analysis of cracked and uncracked concrete cores from the older bridges in this study did not show pronounced preferential chlo...

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Corrosion Performance of Concrete Cylinder Piles

The extent of corrosion of epoxy-coated rebar (ECR) in marine bridges was found to be generally correlated with concrete chloride diffusivity, DApp, with significant corrosion observed for bridges with DApp values reaching up to ∼10−7 cm2/s but not for sound concrete locations in bridges with DApp approaching the order of 10−9 cm2/s. However, significant ECR corrosion was observed in several preexisting cracked concrete locations of a low DApp bridge after only ∼15 years of service. Well-manifested, enhanced chloride and moisture penetration took place through the preexisting cracks of this bridge. The corrosion products in that case were solid and grew underneath the epoxy coating and had a composition consistent with that of chloride-substituted Akaganeite (β-FeO[OH]). Laboratory experiments showed that oxygen presence was not necessary for the formation of similar corrosion products, suggesting that corrosion damage could develop even with thin, moisture-filled cracks that would restrict oxyge...

Corrosion of Epoxy-Coated Rebar in Marine Bridges—Part 2: Corrosion in Cracked Concrete

In 1986 the first signs of corrosion of epoxy-coated rebar were observed in the Long Key Bridge Substructure. Further investigations revealed extensive corrosion of epoxy-coated rebars in four of the five major structures in the Florida Keys. A Task Force was established to investigate the problem by conducting in house research, contract research and a statewide survey of bridges with epoxy-coated rebar substructures. As a result of the investigation it was concluded that epoxy-coated rebar is unsuitable for marine splash zone corrosion protection.

R.G. Powers

Papers

Surface Resistivity as an Indicator of Concrete Chloride Penetration Resistance

Corrosion of Epoxy-Coated Rebar in Marine Bridges—Part 1: A 30-Year Perspective

Corrosion Performance of Concrete Cylinder Piles

Corrosion of Epoxy-Coated Rebar in Marine Bridges—Part 2: Corrosion in Cracked Concrete

Corrosion of epoxy-coated rebar in a marine environment