Corrosion Of Steel Rebar Research Articles

Crevice corrosion of steel rebar in chloride-contaminated concrete

In this paper, crevice corrosion was proposed as one of the important mechanisms responsible for the damage of steel rebar in concrete, which was experimentally verified in simulated concrete pore solution (SCPS) and concrete blocks. The effects of chloride concentration and temperature on the crevice corrosion were comparatively investigated by means of potentiodynamic polarization, immersion, electrochemical impedance spectroscopy (EIS) and galvanic current measurements. The crevice corrosion products in chloride-contaminated SCPS were examined by X-ray photoelectron spectroscopy (XPS). The results indicated that chloride contamination and temperature elevation could significantly accelerate the crevice corrosion.

Corrosion of Steel Rebars in Anoxic Environments. Part II: Pit Growth Rate and Mechanical Strength.

Reinforced concrete may corrode in anoxic environments such as offshore structures. Under such conditions the reinforcement fails to passivate completely, irrespective of chloride content, and the corrosion taking place locally induces the growth of discrete pits. This study characterised such pits and simulated their growth from experimentally determined electrochemical parameters. Pit morphology was assessed with an optical profilometer. A finite element model was developed to simulate pit growth based on electrochemical parameters for different cathode areas. The model was able to predict long-term pit growth by deformed geometry set up. Simulations showed that pit growth-related corrosion tends to maximise as cathode area declines, which lower the pitting factor. The mechanical strength developed by the passive and prestressed rebar throughout its service life was also estimated. Passive rebar strength may drop by nearly 20% over 100 years, whilst in the presence of cracking from the base of the pit steel strength may decline by over 40%.

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

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.

Investigation of the mechanical and durability properties of sustainable high performance concrete based on calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cement could be a promising alternative to ordinary Portland cement (OPC) to reduce environmental impact of concrete production. This paper investigates the performance of high performance concretes produced with CSA cement in total or partial substitution of OPC (or OPC with ground granulated blast-furnace slag (GGBS)) at water-binder ratio of 0.35. Mechanical, physical, durability, and microstructural properties of different concretes were assessed. The results show that substitution of OPC with CSA cement improves the mechanical properties of concrete . The addition of CSA cement results in a reduced shrinkage deformation, while it increases the risk of carbonation and corrosion of steel rebars . Combination of CSA cement with OPC and GGBS in the binary and ternary systems causes a reduction of the strengths of concrete, and adversely affects the durability properties. The SEM observation show that ettringite crystals decomposed in the CSA-blended mixes and resulted in the formation of carbonated phases. • High performance concretes were developed with calcium sulfoaluminate (CSA) cement. • Ground granulated blast-furnace slag was utilized in ternary blended concrete mix. • Linear correlation between resistivity and compressive strength was obtained. • Electrical resistivity of CSA mixes can lead to misleading indication on corrosion. • The addition of CSA cement increases the risk of steel rebars corrosion.

KAJIAN MODEL MATSUOKA PADA KOROSI BAJA TULANGAN BETON

Modified Matsuoka model had been proven giving satisfactory fitting to EIS (electrochemical impedance spectroscopy) data on steel rebar corrosion. To understand complete phenomenon on steel rebar corrosion, computer simulation was used. The value of model parameter was changed and Nyquist diagrams were developed. Nyquist diagrams were used to understand the corrosion phenomenon because of the changing of model parameter. From the simulation, it found that warburg impedance must be multiply by O. 707 from infinite warburg impedance equation. It means that ion diffusion in concrete is follow to finite warbug impedance. W, R4, R6 and Rs showed significant influence to corrosion rates. C1, C2, C3, C4, Cdt and R5 parameters did not show significant influence to corrosion rates. Low frequency on EIS measurement showed significant influence to corrosion rate than high ones.

Cementitious materials containing nano-carriers and silica for the restoration of damaged concrete-based monuments

The conservation of damaged concrete-based monuments is a demanding challenge for the contemporary world of cultural heritage, given the great number of historic concrete-based monuments built in the last century that are prone to continuous damages. In this work, we developed three different cement-based formulations to address the repair of diverse types of damages that affect these structures, i.e. delamination problems and cracks of different size. Formulations were improved with various additives, in order to obtain an easy application, a good workability of the paste and a proper setting time, according to the specific application. Silica was included in the formulations to enhance the adhesion to old concrete substrates, whereas halloysite nanotubes loaded with a corrosion inhibitor were also incorporated in the repair materials, to address in an innovative way the problem of corrosion of steel rebars. The formulations were characterized with a multi-technique approach, which allowed us to get a complete overview of the physico–chemical features of these repair materials. In addition, the adhesion of the formulations to old concrete substrates was investigated, as well as the release of the corrosion inhibitor within the cement matrix. Given the promising results obtained, the formulations were applied at the War Memorial of Torricella Peligna (Italy), confirming their great potentialities in the field of historic concrete-based monuments conservation.

An 18-Month Analysis of Bond Strength of Hot-Dip Galvanized Reinforcing Steel B500SP and S235JR+AR to Chloride Contaminated Concrete.

This article describes the comparative analysis of tests on bond strength of hot-dip galvanized and black steel to concrete with and without chlorides. The bond effect was evaluated with six research methods: strength, electrochemical (measurements of potential, EIS and LPR), optical, and 3D scanning. The tests were conducted within a long period of 18 months on 48 test elements reinforced with smooth rebars ϕ8 mm from steel grade S235JR+AR and ribbed rebars ϕ8 mm and ϕ16 mm from steel grade B500SP. The main strength tests on the reinforcement bond to concrete were used to compare forces pulling out galvanized and black steel rebars from concrete. This comparative analysis was performed after 28, 180, and 540 days from the preparation of the elements. The electrochemical tests were performed to evaluate corrosion of steel rebars in concrete, particularly in chloride contaminated concrete. The behaviour of concrete elements while pulling out the rebar was observed using the system of digital cameras during the optical tests. As regards 3D scanning of ribbed rebars ϕ8 mm and ϕ16 mm, this method allowed the detailed identification of their complex geometry in terms of determining the polarization area to evaluate the corrosion rate of reinforcement in concrete. The test results indicated that the presence of zinc coating on rebars had an impact on the parameters of anchorage. In the case of ribbed rebars of 16 mm in diameter, the maximum values of adhesive stress and bond stiffness were reduced over time when compared to black steel rebars. Moreover, it was noticed that the stiffness of rebar anchorage in chloride contaminated concrete was considerably higher than in concrete without chlorides.

Fatigue behavior of corroded reinforced concrete continuous beams with multi-intervention system

The corrosion of steel rebars in reinforced concrete (RC) structures will lead to the deterioration of fatigue performance and fatigue life. For the sake of resolving the corrosion problems of RC structures, the Impressed Current Cathodic Protection (ICCP) and Structural Strengthening (SS) techniques are often applied to repair the corroded RC structures. In this study, the ICCP-SS techniques are combined to retrofit the deteriorated RC continuous beams by using the carbon-fabric reinforced cementitious matrix (C-FRCM), and the C-FRCM composites comprised of carbon fabric mesh and inorganic cementitious matrix will served as anodic material for ICCP and the structural strengthening material in the ICCP-SS multi-intervention system. By analyzing the test results of fatigue life, failure mode, cracks in concrete, mid-span deflection, tensile strain of steel rebars and internal force redistributions of the test beams under fatigue load, the influence of reinforcement corrosion and the ICCP-SS retrofitting method on the fatigue performance of RC continuous beams were discussed. The test results showed that the strengthening effect of C-FRCM composites can reduce the generation of cracks in concrete and improve the flexural rigidity as well as fatigue life of the continuous beams effectively, however, the improving effect will decrease for the specimens with higher circulated charge density along with a higher polarization effect of C-FRCM composites.

Triple-functional carbon fibre reinforced polymer for strengthening and protecting reinforced concrete structures

Carbon fibre reinforced polymers (CFRP) are innovative composite materials that have been applied for repairing and retrofitting civil engineering structures. In this work, long-term performance tests have demonstrated that the CFRP can not only perform as a strengthening material for reinforced concrete (RC), but also can simultaneously perform as a protective coating layer and an impressed current cathodic protection (ICCP) anode for protecting steel rebar from corrosion. It is shown that the CFRP coating layer is partially protective, reducing steel rebar corrosion and ICCP current requirements. A reduced ICCP current density of 20 mA/m2 avoided ICCP induced CFRP damage, permitting long-term protection and strengthening of RC structures.

Effect of the chloride environmental exposure on the flexural performance of strengthened RC beams with self-anchored prestressed CFRP plates

Carbon fibre-reinforced polymer (CFRP) plates are widely used to strengthen reinforced-concrete (RC) structures. At present, most studies focused on the short-term performance of strengthened RC beams with a prestressed CFRP plate, and very limited information is available on their durability, which is of importance in certain cases, such as high-piled wharfs and bridges in marine environments. This study investigates the effects of chloride environment exposure on the flexural performance of strengthened RC beams with self-anchored prestressed CFRP plates. In total, seven RC beams, four of which were strengthened by a self-anchored prestressed CFRP plate, were fabricated and tested under three-point bending. The testing parameters included 25% and 40% prestress level of the ultimate tensile strength of the CFRP plate, 5% and 10% tensile steel rebar corrosion ratio of mass loss and 10% and 20% anchor corrosion ratio in the chloride environment. The evolution of time-dependent prestress losses in the strengthened beam was determined, and the flexural behaviour of the strengthened beams was analysed. A theoretical model is proposed to predict the flexural strength of prestressed CFRP strengthened RC beams in a chloride environment. The experimental results indicated that the coupling of the corrosion expansion of the metal anchor and rebar in the chloride environment had a large negative effect on the flexural performance of the beams strengthened by the self-anchored prestressed CFRP plates. After exposure to the chloride ion solution, the failure mode of the RC beams strengthened by the prestressed CFRP changed from concrete crushing in the compression section to anchor pullout. The proposed model, which considered the effect of a chloride environment to predict the flexural strength of the strengthened beams, agreed well with the test results.

Protection against reinforcement corrosion using various hydroxy acid-based rust converters: tests in mortar medium

This study investigates the protective effect of various hydroxy acid-based rust converters such as malic acid, tartaric acid, lactic acid, hydroxy acid mixture and glycolic acid in controlling the corrosion of steel reinforcement embedded in cement mortar. The steel rebars pre-treated with hydroxy acids were embedded in cement mortar samples. Afterward, the reinforced samples were exposed to 2.5% sodium chloride (NaCl) and 2.5% magnesium sulphate (MgSO4) solution for 52 weeks (∼365 days). The corrosion state of rebars was estimated in terms of visual assessment of steel rebars, electrical resistivity (ER), corrosion current density based on linear polarisation resistance (LPR) and half-cell potential (HCP) values. The results indicate that the rebar specimens treated with malic, tartaric, lactic and hydroxy acid mixture underwent a lower degree of corrosion-related deterioration. This inhibition effect on the corrosion of steel rebars is due to the formation of insoluble complexes and chelates, leading to the preservation of hydration products in the samples collected from the steel–mortar interface as evidenced by SEM, XRD and FTIR spectroscopy.

Ground penetrating radar for assessment of reinforced concrete wastewater treatment plant

During their long-term service, wastewater treatment plants deteriorate due to rebar corrosion in concrete structures. This paper presents a case study of ground penetrating radar (GPR) survey performed on a reinforced concrete (RC) structure in sieving unit of the wastewater treatment plant in the City of Fortaleza, Brazil. The RC structure was subjected to both the sulfuric acid attack from the oxidation of hydrogen sulfide present in the wastewater gas and the cyclic dry–wet salt-fog environment due to its proximity to the ocean. The survey results suggest that the amplitude of electromagnetic waves from a GPR scan and the determined dielectric permittivity values can be used to monitor steel rebar corrosion in a concrete structure by rapidly detecting any growth of inherent faults. The results indicate that the rebar condition can be assessed through slices at different times/depths obtained from a three-dimensional (3D) survey. Based on this study, it is recommended that the upper RC slabs in sieving unit of the plant be demolished and the lower slabs be preserved.

Bond degradation of non-uniformly corroded steel rebars in concrete

In this work, the bond degradation of non-uniformly corroded steel rebars embedded in concrete was studied. A total of 105 concrete specimens with accelerated corrosion of steel rebar were evaluated using the pull-out test. The influences of corrosion mode, corrosion level, orientation of the longitudinal rib, and the position of steel rebar on the bond degradation were analyzed. The cracking patterns of corrosion-induced cracks, bond failure modes, and bond stress-slip relations were discussed. The results showed that the orientation of longitudinal rib and the thickness of concrete cover play a vital role in determining the cracking patterns of corrosion-induced cracks. In comparison to the uniformly corroded specimens, the bond performance of specimens with non-uniform corrosion of steel rebar degraded more significantly, and this phenomenon became even more pronounced as the corrosion level increased. Moreover, the beneficial improvements caused by the expansive rust on the bond performance were greatly dependent on the degrees of concrete constraint and corrosion level.

Combined impact of carbonation and crack width on the Chloride Penetration and Corrosion Resistance of Concrete Structures

Chloride-induced corrosion of steel rebar embedded in concrete is one of the major concerns influencing the durability of reinforced concrete structures. It is widely recognized that the carbonation in concrete affects the chloride diffusivity and accelerates chloride-induced reinforcement corrosion. The service load-related cracks also have a dominant influence on reinforcement corrosion. This study aims to investigate the potential impact of concrete carbonation on the chloride penetration resistance, and the rate of corrosion, in RC structures subjected to service-related cracks, which is not yet fully understood within the literature. The experimental programme involves casting concrete prisms (100 × 100 × 500 mm) with different water-cement ratios of 0.4, 0.5 and 0.6 and with four different crack width ranges (0, 0.05–0.15 mm, 0.15–0.25 mm and 0.25–0.35 mm), developed through flexural loading of prisms. These samples were exposed initially to accelerated carbon dioxide (CO2) environment and then exposed to the accelerated chloride environment. Carbonation depth, chloride penetration, and the degree of corrosion (using half-cell potential and linear polarization resistance) were experimentally measured. The results indicated that (i): The depth of carbonation increases with the increase in crack width and w/c ratio, (ii) chloride penetration depth and chloride concentration profile in concrete structures increases significantly due to the influence of carbonation and (iii) half-cell corrosion potential and linear polarization resistance increases significantly when carbonated concrete samples are exposed to the chloride environment relative to the uncarbonated concrete samples.

Design of Concrete Building Structure in Marine Corrosion Zones

Zhao, H.R., 2020. Design of concrete building structure in marine corrosion zones. In: Al-Tarawneh, O. and Megahed, A. (eds.), Recent Developments of Port, Marine, and Ocean Engineering. Journal of Coastal Research, Special Issue No. 110, pp. 266–270. Coconut Creek (Florida), ISSN 0749-0208.Building structures in offshore areas are extremely susceptible to chloride ion erosion in seawater or marine atmospheric environment, causing problems such as corrosion and swelling of steel rebar, spalling of concrete protective layer, etc., reducing the service life of the structure, and increasing the maintenance and operating costs of the structure. This paper attempts to enhance the design concrete building structures in the marine corrosion zones from the two aspects of durability and service life. To this end, it summarizes the principles of chloride ion erosion of reinforced concrete structures in coastal areas based on existing research, and explores the destruction mechanism of reinforced concrete structures under the action of chloride ions and external loads. Finally, the new method suitable for durability design of reinforced concrete structures in marine corrosion zone was proposed. The study found that the chloride-induced corrosion to the structure in the marine environment can cause the corrosion of the steel bars and accelerate the corrosion rate; a time-varying reliability model of the reinforced concrete structure was proposed; the increase in the thickness of the steel protective layer in the concrete can effectively improve the durability and service life of the structure. The research findings provide a theoretical basis for the durability design of concrete structures in offshore environments or marine corrosion zones.

Seismic capacity and vulnerability assessment considering ageing effects: case study—three local Portuguese RC buildings

A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.

Ammonium Phosphate as Inhibitor to Mitigate the Corrosion of Steel Rebar in Chloride Contaminated Concrete Pore Solution.

In the present study, different amounts, i.e., 1–3 v/v% of 1 M ammonium phosphate monobasic, were used as an eco-friendly corrosion inhibitor to mitigate the corrosion of steel rebar exposed to simulated concrete pore (SCP) + 3.5 wt% NaCl solution at a prolonged duration. Potentiodynamic polarization results show that as the amount of inhibitor is increased, the corrosion resistance of steel rebar is increased. The steel rebar exposed to 3% inhibitor-containing SCP + 3.5 wt% NaCl solution exhibited nobler corrosion potential (Ecorr), the lowest corrosion current density (icorr), and 97.62% corrosion inhibition efficiency after 1 h of exposure. The steel rebars exposed to 3% inhibitor-containing SCP + 3.5 wt% NaCl solution revealed higher polarization resistance (Rp) and film resistance (Ro) with exposure periods compared to other samples owing to the formation of passive film. The scanning electron microscopy (SEM) of steel rebar exposed to 3% inhibitor-containing SCP + 3.5 wt% NaCl solution showed homogenous and uniform dendritic passive film which covers all over the surface, whereas, bare, i.e., SCP + 3.5 wt% NaCl solution exposed samples exhibited pitting and irregular morphology. Raman spectroscopy results confirm the formation of goethite (α-FeOOH), maghemite (γ-Fe2O3), and iron phosphate (FePO4) as a passive film onto the steel rebar surface exposed to 3% inhibitor-containing SCP + 3.5 wt% NaCl solution. These phases are responsible for the corrosion mitigation of steel rebar which are very protective, adherent, and sparingly soluble.

Effect of Phosphate-Based Inhibitor on Corrosion Kinetics and Mechanism for Formation of Passive Film onto the Steel Rebar in Chloride-Containing Pore Solution.

In the present study, different contents, i.e., 1–3% of 0.5 M ammonium phosphate mono basic (APMB), were used as corrosion inhibitor to reduce the corrosion of steel rebar. Electrochemical impedance spectroscopy (EIS) results showed that up to 24 h of exposure, polarization resistance (Rp) and passive/oxide film resistance (Ro) gradually decreased in simulated concrete pore (SCP) + 3.5 wt.% NaCl solution owing to the reduction in pH of the solution. The steel rebar exposed in 2% inhibitor containing SCP + 3.5 wt.% NaCl solution exhibited 90% inhibition efficiency after 1 h of exposure. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed the formation of thermodynamically very stable and sparingly soluble goethite (α-FeOOH), maghemite (γ-Fe2O3), and iron phosphate (FePO4) as passive/oxide film onto the steel rebar surface exposed to 2% inhibitor containing SCP + 3.5 wt.% NaCl solution.

Fatigue behavior of GFRP-reinforced ECC link slabs under variable stress levels and number of cycles

Glass Fibre Reinforced Polymer (GFRP) bars have been used in the Province of Ontario as top layer of bridge deck reinforcement near surfaces exposed to de-icing chemicals. The intent of replacing deck reinforcements with GFRP is to mitigate negative effects of conventional steel rebar corrosion. Furthermore, the development of Engineered Cementitious Composite (ECC) with inherent crack width control and strain-hardening tensile behaviour for link slab application provides design engineers with a new effective way to construct joint-free bridge decks with improved durability. This paper presents experimental investigation of ECC-link slabs reinforced with sand-coated GFRP bars. The link slab specimens were subjected to variable mean fatigue stress levels of up to 55% load capacity and fatigue cycles of up to 1 million, followed by post-fatigue monotonic loading to failure. Link slab load–deflection, stiffness degradation, end rotation, GFRP and ECC strains, crack development, failure modes, energy absorbing capacity, and ductility were determined. Results were then compared with companion steel-reinforced ECC link slabs in the literature to quantify benefits of using GFRP bars. Experimental results showed that GFRP-reinforced link slabs failure by concrete crushing due to high rupture strength of GFRP, whereas steel-reinforced link slabs failed by rebar yielding. Besides exhibiting improved overall strength, the GFRP reinforced ECC link slabs showed greater post-fatigue residual rotational capacity, lower rate of stiffness degradation, enhanced post-fatigue retention of energy absorbing capacity.

Corrosion resistance evaluation of rebars with various primers and coatings in concrete modified with different additives

Corrosion of steel rebars in concrete can reduce the durability of concrete structures in coastal environments. The corrosion rate of these concrete structures can be reduced by using suitable concrete additives and coating on rebars. This paper investigates the corrosion resistance of steel rebars by the addition of pozzolanic materials including fly ash, silica fume, polypropylene fibers, and industrial 2-dimethylaminoethanol (FerroGard 901) inhibitors to the concrete mixture. Three different types of rebars including mild steel rebar st37, and two stainless steel reinforcements, AISI 304 and AISI 316, were used. Various types of primer and coating including alkyd based primer, hot-dip galvanized coatings, alkyd top coating, zinc-rich epoxy primer, polyamide epoxy primer, polyamide epoxy top coating, polyurethane coatings, double layer of epoxy primer and alkyd top coating, and double layer of alkyd primer and alkyd top coating were applied on steel rebars to investigate the effect of coating type on the corrosion resistance of steel rebars in concrete. Polarization tests, electrochemical impedance spectroscopy, compressive strength and color adhesion tests were conducted. The best reinforced concrete mix design for corrosion resistance was the one including the rebar with zinc-rich epoxy primer and 25% fly ash, 10% silica fume, and 3% FerroGard 901 inhibitors by cementitious material weight. Polyurethane was the best coating due to the highest strength and the lowest corrosion rate. Alkyd primer was the weakest coating, although it was the most economical coating system.