Corrosion-resistant Reinforcement Research Articles

Streamlined Framework to Select Corrosion-Resistant Reinforcement to Balance Life-Cycle Costs and Ductility of Concrete Bridge Decks

Streamlined Framework to Select Corrosion-Resistant Reinforcement to Balance Life-Cycle Costs and Ductility of Concrete Bridge Decks

Practical Approaches to Long-Lasting Bridge Decks

Concrete bridge decks are susceptible to deterioration, mainly in the form of cracking, spalling, and delaminations; this adversely affects the ride quality and structural integrity. Causes of deterioration are excessive loading, adverse environmental conditions, chemical reactions, electrochemical corrosion, poor structural design and detailing, improper construction practices, and insufficient specifications. Cracks in bridge decks provide avenues for water and solutions, mainly the chlorides, to penetrate the concrete and substantially diminish its service life. To achieve longer-lasting bridges, the quality of both the concrete and the reinforcement must be considered. The occurrence and width of cracks in bridge decks can be reduced using high-quality concrete and corrosion-resistant reinforcement. This paper details practical approaches to achieving long-lasting bridge decks through proper attention to design, selection of materials, construction practices, and specifications.

Axial bearing capacity and ductility of seawater sea sand coral aggregate concrete (SSCC) columns reinforced with hybrid GFRP and corrosion resistant rebars

The shortage of fresh water and river sand resources and steel corrosion are becoming increasingly prominent in engineering construction. Seawater sea sand coral aggregate concrete (SSCC) and corrosion resistant reinforcement are promising materials in replacement of conventional concrete and steel in building structures in island and reef construction. This study investigated the axial compression performance of GFRP (glass fiber reinforced polymer) and corrosion resistant rebars hybrid reinforced seawater sea sand coral aggregate concrete columns. A total of eighteen short columns were tested for axial compression performance, including three reinforcement ratios (1.01%, 1.56%, 2.26%) and 5 reinforcement types (pure GFRP reinforcement or G, pure stainless steel reinforcement or S, pure epoxy coated steel rebar (ECSB) reinforcement or E, GFRP-stainless steel reinforcement or GS and GFRP-ECSB or GE). The failure modes of the column are recorded and analyzed, and the axial bearing capacity and ductility are calculated and analyzed. Results show that the bearing capacity of columns is positively correlated with the reinforcement ratio. Generally, the bearing capacity of S-SSCC column and E-SSCC column are not significant different, but both are larger than that of G-SSCC column. The bearing capacity of hybrid reinforcement GS-SSCC and GE-SSCC column is between S-SSCC column and G-SSCC column. Meanwhile, it indicates that the theoretical calculation results of bearing capacity agree well with the experimental results. The ductility analytical results exhibit that the studied column specimens have the highest ductility when the reinforcement ratio is 1.56%. Among different reinforcement types, the ductility of G-SSCC is the smallest and the GE-SSCC and GS-SSCC column show improved ductility compared with G-SSCC columns.

Investigation of Helix-Pultruded CFRP Rebar Geometry Variants for Carbon-Reinforced Concrete Structures.

Carbon concrete is a new, promising class of materials in the construction industry. This corrosion-resistant reinforcement material leads to a reduction in the concrete cover required for medial shielding. This enables lean construction and the conservation of concrete and energy-intensive cement manufacturing. Bar-type reinforcement is essential for heavily loaded structures. The newly developed helix pultrusion is the first process capable of producing carbon fiber-reinforced polymer (CFRP) reinforcement bars with a topological surface in a single pultrusion process step, with fiber orientation tailored to the specific loads. The manufacturing feasibility and load-bearing capacity were thoroughly tested and compared with other design and process variants. Approaches to increase stiffness and strength while maintaining good concrete anchorage have been presented and fabricated. Tensile testing of the helical rebar variants with a 7.2 mm lead-bearing cross-section was conducted using adapted wedge grips with a 300 mm restraint length. The new helix geometry variants achieved, on average, 40% higher strengths and almost reached the values of the base material. Concrete pull-out tests were carried out to evaluate the bond properties. The helix contour design caused the bar to twist out of the concrete test specimen. Utilizing the Rilem beam test setup, the helical contour bars could also be tested. Compared with the original helix variant, the pull-out forces could be increased from 8.5 kN to up to 22.4 kN, i.e., by a factor of 2.5. It was thus possible to derive a preferred solution that is optimally suited for use in carbon concrete.

Non-uniform corrosion influences on mechanical performances of stainless-clad bimetallic steel bars

As a type of corrosion-resistant reinforcement, the stainless-clad bimetallic steel bar (SCBSB) has the advantages of low price and good mechanical properties, which causes them to be widely used in engineering structures. In the actual service process of the structure, the steel bar always corrodes first on the side close to the concrete cover. This type of non-uniform corrosion characteristic may lead to the mechanical properties of steel bars being very different from those with ideal uniform corrosion. Therefore, studying the degradation law of the mechanical properties of SCBSBs with non-uniform corrosion has important engineering value and research significance. In this study, the non-uniform corrosion mechanism was described, and non-uniformly corroded SCBSB specimens at different corrosion degrees were obtained by the electrochemical accelerated corrosion method. Through tests and analyses, the mechanical properties and toughness degradation laws of the SCBSB with non-uniform corrosion were obtained. Models were proposed to predict the mechanical properties and toughness of SCBSBs with non-uniform corrosion at any corrosion degree. In addition, through a finite element analysis, the mechanical property degradation laws of SCBSBs with three corrosion forms were analyzed. According to the experimental results, it was suggested that the corrosion degree of SCBSBs should be controlled within 14.39% to meet engineering requirements. The resistances of reinforced concrete beam with different corroded degrees SCBSBs were discussed to clarify the effect of corrosion type on durability of reinforced concrete members.

COLUMN CONFINEMENT WITH TEXTILE-REINFORCED CONCRETE (TRC)

Textile reinforced concrete (TRC) is an innovative composite material consisting of a fine-grained concrete matrix and a textile reinforcement. Due to the corrosion-resistant reinforcement, the concrete cover, which is necessary for reinforced concrete constructions, can be reduced. Combining the tensile mechanical properties of carbon fibers with the compressive strength of fine-grained high-strength concrete, TRC can be seen as an efficient alternative to the previous reinforcement and strengthening measures for concrete columns. By confining the column with TRC, the lateral expansion of the concrete can be impeded. The resulting multiaxial compressive stress state allows to enhance the concretes compressive strength. The aim of this study is the investigation of various influences on the achievable strengthening effect. With the help of experiments on TRC, reinforced columns with circular cross-section mechanical property and constraint mechanism under uniaxial compression were documented and analyzed. Based on the test results, stress distribution and failure mechanisms of the reinforced specimens are studied. Furthermore, the load-displacement relationship of strengthened members is investigated. The effect of the ratio of textile reinforcement, section dimension and concrete strength on the ultimate strength of strengthened members is also evaluated.

COLUMN CONFINEMENT WITH TEXTILE-REINFORCED CONCRETE (TRC)

Textile reinforced concrete (TRC) is an innovative composite material consisting of a fine-grained concrete matrix and a textile reinforcement. Due to the corrosion-resistant reinforcement, the concrete cover, which is necessary for reinforced concrete constructions, can be reduced. Combining the tensile mechanical properties of carbon fibers with the compressive strength of fine-grained high-strength concrete, TRC can be seen as an efficient alternative to the previous reinforcement and strengthening measures for concrete columns. By confining the column with TRC, the lateral expansion of the concrete can be impeded. The resulting multiaxial compressive stress state allows to enhance the concretes compressive strength. The aim of this study is the investigation of various influences on the achievable strengthening effect. With the help of experiments on TRC, reinforced columns with circular cross-section mechanical property and constraint mechanism under uniaxial compression were documented and analyzed. Based on the test results, stress distribution and failure mechanisms of the reinforced specimens are studied. Furthermore, the load-displacement relationship of strengthened members is investigated. The effect of the ratio of textile reinforcement, section dimension and concrete strength on the ultimate strength of strengthened members is also evaluated.

The Improvement of Durability of Reinforced Concretes for Sustainable Structures: A Review on Different Approaches.

The topic of sustainability of reinforced concrete structures is strictly related with their durability in aggressive environments. In particular, at equal environmental impact, the higher the durability of construction materials, the higher the sustainability. The present review deals with the possible strategies aimed at producing sustainable and durable reinforced concrete structures in different environments. It focuses on the design methodologies as well as the use of unconventional corrosion-resistant reinforcements, alternative binders to Portland cement, and innovative or traditional solutions for reinforced concrete protection and prevention against rebars corrosion such as corrosion inhibitors, coatings, self-healing techniques, and waterproofing aggregates. Analysis of the scientific literature highlights that there is no preferential way for the production of “green” concrete but that the sustainability of the building materials can only be achieved by implementing simultaneous multiple strategies aimed at reducing environmental impact and improving both durability and performances.

A probabilistic framework for life-cycle cost analysis of bridge decks constructed with different reinforcement alternatives

Reinforced concrete bridge decks with conventional reinforcement may experience deterioration due to deicing salts or marine environmental conditions. Routine maintenance, rehabilitation, and repair activities are implemented to maintain an acceptable performance level. In addition to the significant financial resources required to conduct these activities, traffic congestions at work zones can lead to an increase in delays and crash risk for road network users, as well as other environmental and social impacts. These user costs arising from traffic congestions can be significantly higher than the cost of maintenance, rehabilitation, and repair activities. Despite the higher initial unit cost, bridge decks constructed with corrosion resistant reinforcement can provide a longer service life and require less maintenance activities. Accordingly, from a life-cycle cost perspective, corrosion resistant reinforcement could be a better alternative compared to conventional reinforcement for bridge decks. This paper presents a probabilistic framework to estimate the life-cycle cost associated with bridge decks constructed with different reinforcement alternatives. The framework accounts for reinforcement deterioration to evaluate the maintenance activity timeline considering influential corrosion-related parameters (e.g., reinforcement type, concrete cover, and bridge location, among others). Key attributes affecting traffic delays, including traffic volume, number of lanes, and vehicular queuing, are also included in the framework. Monte Carlo simulation is used to predict the corrosion-induced cracking time, service life of the bridge deck, and the life-cycle cost under uncertainty. A bridge located in Pennsylvania is used as an illustrative example to demonstrate the application of the proposed framework. The results show that the concrete cover, chloride exposure condition, average daily traffic, and number of traffic lanes have a significant effect on the life-cycle cost of reinforced concrete bridge decks; especially for those constructed with conventional reinforcement. The presented framework can be beneficial in selecting the optimum bridge deck reinforcement type from a life-cycle cost perspective.

Axial compression capacity of concrete columns reinforced with corrosion-resistant metallic reinforcement

Axial compression performance of concrete columns reinforced with 2304 solid stainless bars and spirals, carbon steel bars and spirals, and 316 L stainless steel clad bars is examined after the columns are exposed to severe corrosion. Two groups of columns were investigated: a control group, and a group submerged in a 5.0% by weight chloride solution subjected to accelerated corrosion. A relatively high impressed current density of 8.5 μA/mm2 was used and after 60 days of accelerated corrosion the columns were tested to failure under axial compression. In terms of mass loss per unit of corrosion energy, columns reinforced with stainless steel spirals and either solid stainless or stainless clad vertical bars were 197% more corrosion resistant than carbon steel. Bars made with 2304 solid stainless steel and 316 L stainless clad materials developed localized pitting corrosion that led to degradation of the concrete cover and a larger drop in axial compression than carbon steel reinforced columns. However, the carbon steel reinforced columns reached lower failure displacements and a corroded carbon steel reinforced column was the only column to experience sudden failure prior to reaching its theoretical maximum axial compression capacity. Axial compression capacity of the columns in both the control and corroded conditions was modeled using concrete confinement models that produced good agreement with the experimental results.

A New Torsion Testing Apparatus for Circular Members

The concrete-filled fiber-reinforced polymer tube (CFFT) is a unique structural element that is well suited for reinforced concrete applications in harsh environments due to the corrosion-resistant reinforcement. It also benefits from the stay-in-place formwork capabilities of the reinforcement and the beneficial concrete confinement offered primarily in cases of axial compression. The strength and response of the CFFT system have been studied under axial, flexural, and combined loading conditions; however, its torsional behavior has not been evaluated. Some of the challenges have been the ability to provide successful gripping of the circular cross-section as well as avoiding the undesired second-order effects when pure torsion is investigated. This paper presents a novel apparatus developed to test circular members, including CFFTs, to failure under a variety of loading conditions including pure torsion, and combined torsion, bending, and axial compression. The apparatus can accommodate a complex set of geometric nonlinearity effects associated with the deformations arising from multiple degrees of freedom. The functionality of the testing system under a state of pure torsion and combined loading was verified. The results showed that the testing apparatus effectively simulated the intended loading condition. The samples experience relatively large and complex displacements that justified the details incorporated in the design of various components of the testing configuration.

A Comprehensive Review on Effects of Seawater on Engineering Properties of Concrete

The concrete and natural seawater have a complex relationship between them, which requires special attention. Therefore, various studies have been conducted to consider the effects of natural seawater on the properties of concrete. However, this study aimed to summarize and analyze the previous findings and recommendations. It was noticed that the natural seawater has both positive and negative implications on concrete. Thus, resistance of concrete against the seawater can be improved by adding supplementary cementitious materials (SCM) like copper slag, coal bottom ash, fly ash and others with appropriate proportions. Moreover, the problem of corrosion of reinforcement due to seawater influence, can be avoided using corrosion inhibitor and/or corrosion resistant reinforcement. It was also noticed that the addition of SCM could increase the performances of concrete like strength and durability of concrete exposed to the marine environment. This paper provides a deep insight about experimental information and future direction for the concrete exposed to the marine environment.

Cracking Behavior of Slabs with Corrosion-Resistant and High-Strength Reinforcing Bars

Cracking Behavior of Slabs with Corrosion-Resistant and High-Strength Reinforcing Bars

Reproducibility of the Corrosion Resistance of UNS S32205 and UNS S32304 Stainless Steel Reinforcing Bars

One strategy to address the 75-year service life requirement of a number of highway bridge design codes is the use of more corrosion-resistant reinforcement. Over the last few decades, many stainless steel grades have become available for reinforcing concrete. Of these, two duplex alloys, UNS S32205 and UNS S32304, have become the preferred choices for major highway structures in North America. The purpose of the present study was to investigate the consistency, or variability, of the corrosion performance of bars of these grades from different steel manufacturers. Metallography, chemical analysis, corrosion resistance, and corrosion product evaluation were used to evaluate the bars. It was found that micropits exist to varying degree in the as-received conditions of these bars and that was the most dominant factor in determining the corrosion performance of the bars.

Progresses in prevention of corrosion in concrete

Rebar corrosion, carbonation or chloride induced, is the most important cause of premature failure of reinforced concrete structures. Prevention of rebars corrosion is of paramount importance to reduce cost, increase reliability and improve sustainability of constructions. This goal can be achieved in design and construction stages by proper concrete mix (w/c ratio and cement type), suitable casting and curing procedures, sufficient concrete cover as a function of environment aggressiveness, according to standards as Eurocode and EN 206. Additional protection methods can be used in very aggressive environment or when very long service life is required. Among these methods, corrosion resistant reinforcements (galvanised or stainless steels), concrete coatings, corrosion inhibitors and cathodic prevention have been proposed in literature and applied in field. In the first part of the paper the most recent achievements of our research group on rebars corrosion prevention are examined. In the second part the evaluation of the initiation time of corrosion of a structure in severe environment exposed to chlorides is carried out by Monte Carlo simulation: the results show that cathodic prevention and stainless steels reinforcements are the most effective methods to guarantee a safe working condition of a reinforced concrete structure in a severe environment.

Seawater and stainless steel bars for sustainable reinforced concrete structures

In Mediterranean countries seawater might become a resource for the concrete production for sustainable construction industry. Nowadays its use, since it might induce the corrosion on ordinary carbon steel bars, is prohibited for the realization of reinforced concrete structures. Within the SeaCon Project, the use of seawater as mixing water has been studied in combination with corrosion-resistant reinforcement. This paper, firstly, discusses the influence of chlorides present in the seawater on the concrete properties related to the durability. Afterwards, the corrosion resistance of austenitic (304L and XM-28) and duplex (23-04 and 22-05) stainless steels reinforcing bars, and for comparison of carbon steel, embedded in alkaline and carbonated concretes made with seawater and subjected to different environmental conditions is evaluated. Results showed that seawater accelerated the early strength of concrete, whilst the carbonation penetration, the capillary suction and water absorption were slightly affected. Corrosion tests showed that corrosion did not initiate on 304L, 23-04 and 22-05 stainless steel bars, despite the presence of chlorides since the beginning even in the most aggressive exposure conditions and when concrete was carbonated; XM-28 reinforcement showed a slight change in corrosion behaviour in carbonated concrete exposed to the harshest conditions.

Culvert Prototype Made with Seawater Concrete: Materials Characterization, Monitoring, and Environmental Impact

Abstract Recent developments in concrete research have considered the possible advantages related to the use of seawater as mixing water for concrete production. Specifically, the SEACON-INFRAVATION project investigated the performance of seawater concrete for the construction of sustainable and durable reinforced concrete structures. Besides laboratory activities aimed at characterizing the performance of seawater concrete and corrosion behavior of various types of embedded reinforcements, a demonstration project was executed in Italy. The prototype consisted of a concrete culvert built along the A1 motorway, close to the city of Piacenza, Italy. The demonstration activities led to testing of the on-site use of seawater and assessment of the corrosion conditions of the embedded reinforcements, allowing a thorough understanding of long-term durability and sustainability. For this purpose, the prototype culvert was divided into six segments; each segment was representative of a combination of type of concrete (reference, seawater, and recycled-asphalt-pavement concrete) and type of reinforcement (carbon steel, austenitic and duplex stainless steels, and glass fiber–reinforced polymer). This article presents concrete mix designs, materials characterization, embedded probes used to monitor the corrosion of the reinforcements, and test results obtained at various stages of execution and service conditions. In addition, a sampling campaign, one year from construction, is included. Finally, mention is made of the life cycle assessment and life cycle cost analyses performed to quantify the long-term benefits of seawater concrete combined with corrosion-resistant reinforcement.

Durability-Related Properties of Concrete Made with Chloride-Contaminated Materials

Abstract Because sustainability issues have a primary importance in the construction field, the use of alternative raw materials in concrete production has been widely studied in recent years, especially considering the fact that freshwater is becoming as precious a resource as virgin stones, which are used as aggregates for both concrete and cement production. However, for the durability of reinforced concrete structures, a negligible chloride content in the raw materials should be guaranteed in order to avoid a premature corrosion initiation on reinforcement. Within the Infravation project SEACON, the possible use of recycled aggregate from salt-contaminated concrete structures, seawater- and chloride-contaminated cement have been studied in combination with corrosion-resistant reinforcement for durable concrete structures. Specifically, the experimental study presented in this article is aimed at investigating the effects of chlorides in the raw materials on the durability-related properties of concrete. To this purpose, different concrete mixtures with chloride-contaminated materials were tested in terms of microstructural analysis, mechanical performance, and transport properties (such as compressive strength, capillary water absorption, chlorides, and carbonation penetration). The characterization of concretes showed that the use of chloride-contaminated materials did not negatively influence the early age microstructural features of the hardened cement paste, except for the presence of chlorides in the cement paste. Overall, chloride contamination did not affect the penetration of the carbonation and the capillary absorption, whereas an influence was observed in the resistance to chloride penetration.

Life-Cycle Cost Analysis of Reinforced Concrete Bridge Decks with Conventional and Corrosion Resistant Reinforcement

Reinforced concrete (RC) bridge decks suffer from corrosion-induced damage due to aggressive environmental conditions or de-icing chemicals. Significant expenditures are typically required to conduct routine maintenance and repairs of affected RC bridges. Compared to conventional steel reinforcement (i.e. black rebar), corrosion resistant reinforcement is initially more expensive but provides longer service life. In this paper, corrosion-induced cracking time, traffic delays associated with bridge deck maintenance, and the environmental impact associated with these activities are integrated into a probabilistic framework to investigate the life-cycle cost of RC bridge decks with conventional and corrosion resistant reinforcement. Monte Carlo simulation is implemented to quantify the probabilistic life-cycle cost of the bridge deck. Preliminary results obtained from this project show that corrosion resistant reinforcement has lower life-cycle cost compared to conventional reinforcement. The indirect cost associated with traffic delays accounts for over 50% of the total life-cycle cost for the investigated case study.

Review on Design Consideration and Code Provisions on Corrosion Resistant Reinforcing Bars

Premature deterioration of reinforced concrete structures due to corrosion of the reinforcing steel is a major concern worldwide. In this study code provisions and design considerations for using corrosion resistant reinforcing steel bars have been discussed at length. The most common corrosion resistant reinforcing bars available today are– Fusion Bonded Epoxy Coated Bars (ASTM A775), Hot Dip Galvanized Steel Bar (ASTMA767), Glass Fiber Reinforced ,Polymer Bars and Stainless Steel Rebars (ASTM A955). Especially in marine environments corrosion of reinforcement is one the major concerns regarding durability of RC Structures. Also parts of any structure that are subjected to intermittent wetting and drying (e.g. bridge piers) and those that are subjected to dampness (e.g. topmost roof slab of a building) are more susceptible to corrosion. It is well known that Bangladesh’s already struggling infrastructure is under a constant threat of deterioration due to various physical and environmental conditions while a huge shortfall in budget exists to ensure periodic maintenance and repair works. Corrosion resistant rebars are globally accepted corrosion resistant system that will ensure the structures can be used till the end of their design lives. While demand for all non-corroding bars is on the rise, expertise of engineers and construction workers in handling these bars should grow as well. Therefore recommended work practices while manufacturing, fabricating and concreting has to be included in the country’s standards and guidelines.