Corrosion-induced Damage Research Articles

Experimental and numerical study on concrete beams reinforced with Basalt FRP bars under static and impact loads

The application of fiber-reinforced-polymer (FRP) bars to reinforce concrete structures could mitigate the corrosion-induced damage of steel reinforcements. No study has been reported in open literature on flexure-critical or shear-critical concrete beams reinforced with Basalt FRP (BFRP) bars under impact loads. In this study, six BFRP bars reinforced concrete beams were tested under quasi-static and impact loads. The test results showed the flexure-critical beams experienced the failure mode changing from flexure-governed under quasi-static loads to flexure-shear combined under impact loads. The shear-critical beams still failed in diagonal shear under impact loads, but experienced severer concrete spalling and more critical diagonal cracks on both sides of the beams. The impact performance of concrete beams with higher strength concrete may not be necessarily superior to that of beams with normal strength concrete due to the increased brittleness. Moreover, a numerical model of the tested beams under impact loads was developed and calibrated in LS-DYNA. Numerical results showed increasing tension reinforcement ratio could change the failure mode from flexure-governed to flexure-shear combined along with the reduced maximum midspan deflection. The BFRP bars reinforced concrete beams had comparable impact resistant performance with the conventional steel reinforced concrete beams

Monitoring of corrosion-induced damage to bolted joints using an active sensing method with piezoceramic transducers

Ensuring adequate tightening of bolted joints is necessary since they are more prone to corrosion in a harsh environment under insufficient preload. To this end, this paper first conducted an accelerated electrochemical corrosion experiment to expedite the corrosion process of bolted connections over different periods. The results show that as the corrosion time is extended, the overall dimensions of the bolt system remarkably decrease. Moreover, according to the mass loss of the bolted joints in 3.5% NaCl solution, the rate of corrosion continuously changes. Then, a real-time monitoring approach based on active sensing was utilized to evaluate the corrosion conditions of bolted joints. The stress wave generated by one piezoceramic transducer propagates through the bolted joints and is captured via another transducer that acts as a sensor. The energy corresponding to the stress wave signal declines during the corrosion process, and the normalized wavelet packet energy index is used to evaluate the degree of damage to the bolted joints. Overall, the health status of the bolted joints is significantly affected by the corrosion time. The proposed active sensing method can accurately monitor the corrosion process of bolted joints. The experimental results verify the feasibility and practicality of the real-time, piezoceramic transducer-enabled method for monitoring the structural health of corroded bolted joints.

Numerical evaluation on the effect of steel bar corrosion on the cyclic behaviour of RC bridge piers

Reinforced concrete (RC) bridges exposed to marine environments significantly suffer from steel bar corrosion. Steel bar corrosion is responsible for strength deterioration of steel and concrete material, damage in steel-concrete bond, spalling of cover concrete, and so on. This study presents a numerical model that can simulate the structural behavior of corroded RC bridge piers under seismic action. In the numerical model, corrosion-induced damage modelled through different constitutive laws for corrosion-induced cracking, concrete and steel properties, and bond between steel and concrete. The numerical model for RC bridge piers is validated using the experimental studies available in the literature. The structural behavior obtained in the numerical analysis, i.e., lateral load resistance capacity, cracking length and crack patterns are in good agreement with the experimental study. The analysis results demonstrated that rebar corrosion significantly deteriorates the structural performance (i.e., load resistance capacity, displacement capacity, etc.) of corroded RC bridge piers. The findings of this study will be useful in assessing the residual structural performance of the RC columns with rebar corrosion.

Uticaj termičkog tretmana retrogresije i ponovnog starenja na mehaničke karakteristike legure EN AW 7049A-T6

Aluminum alloys of 7xxx series have the highest strength among all aluminium alloys, but they are prone to the corrosion-induced damage. The retrogression and re-aging heat treatment (RRA) is a heat treatment process applied on the 7xxx series aluminum alloy in T6 temper condition to provide a significant improvement of the corrosion resistance with or without small loss in its strength. The paper presents the influence of RRA treatment on the electrical conductivity and mechanical properties of the aluminum EN AW 7049A-T6 alloy. The retrogression heat treatment was performed at various temperatures (from 180 C to 280 C) and times (from 3 min to 45 min), while re-aging was performed at 120 °C for 24 hours. It has been found that with increasing both temperature and time of retrogression, hardness and strength decrease but the toughness of the alloy increases in comparison to the initial T6 temper. Contrary to hardness values, electrical conductivity rises with an increase in holding time and temperature of retrogression.

Titanium-Silicon on CoCr Alloy for Load-Bearing Implants Using Directed Energy Deposition-Based Additive Manufacturing.

Cobalt-chromium (CoCr) alloys offer outstanding wear resistance when compared to other biocompatible metallic materials and are extensively used in articulating surfaces of total hip and knee arthroplasty. However, CoCr alloys' biocompatibility is known to be inferior to titanium (Ti). Wear- and corrosion-induced metal-ion release from CoCr alloys has been reported to cause cancer and negative physiological impacts. In this study, CoCr alloy was coated with commercially pure Ti (CpTi) and CpTi-Silicon (CoCrTi-Si) with the specific objective of reducing Co and Cr ion release during articulation, without degrading the excellent wear resistance of the CoCr alloy. Directed energy deposition (DED), a blown powder-based laser additive manufacturing technique, was utilized to process CpTi- and CpTi-Si-based coatings on Stellite 6B commercial CoCr alloy. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses, and hardness testing found that refined carbides and titanium silicides increased the hardness from 321 ± 13 to 758 ± 48 HV0.5. Tribological studies determined a comparable wear rate between Stellite 6B alloy and CoCrTi-Si in DI water but a statistically significant reduction in Dulbecco's Modified Eagle Medium (DMEM). The wear rates for Stellite 6B were 8.5 ± 0.8 × 10-5 and 12.9 ± 0.4 × 10-5 mm3/Nm in DI water and DMEM, respectively. While the wear rates for CoCrTi-Si were 9.1 ± 0.5 × 10-5 and 8.9 ± 0.8 × 10-5 mm3/Nm in DI water and DMEM, respectively. Contact resistance acquisition displayed the presence of a passive film formation during tribological testing. ICP-MS results for Stellite 6B and CoCrTi-Si concluded a reduction of Co ions release in DI water from 149.8 ± 66.7 to 17.5 ± 0.7 ppb and a reduction in Cr ions release from 66.7 ± 32.4 to 18.0 ± 0.5 ppb, respectively. In DMEM media, Co ion release for Stellite 6B and CoCrTi-Si reduced from 10.1 ± 1.4 to 4.1 ± 0.2 ppb and Cr ion release for Stellite 6B and CoCrTi-Si reduced from 8.7 ± 0.2 to 5.0 ± 0.7 ppb, respectively. The current study revealed a new mode of manufacturing for CoCr alloy-based load-bearing implants that can reduce toxic metal ions release due to wear- and corrosion-induced damages.

Investigation on failure mechanism of stiffened plates with pitting corrosion under uniaxial compression

The uniaxial compressive behavior of stiffened plates with pitting corrosion is investigated, with a specific concern about corrosion-caused transition within different failure modes. To control the geometrical parameters and distributions of corrosion pits, ten specimens with mechanically-drilled cylindrical corrosion pits near the weld seams are deliberately prepared and tested. During the test, the effects of these influential factors on the complete axial load vs. response curves and failure mechanism are studied. To develop a conceptualized model for physically addressing the coupled load-corrosion effect on the failure modes of stiffened plates, some necessary numerical simulations are supplemented. From the test and simulation results, corrosion can cause a significant variation in the redistribution of internal forces among the constituent components of the stiffened plates. If corrosion-induced damage in the stiffener and plate is comparable, a stiffened plate would experience a transition between plate buckling and eventual stiffener tripping. The proposed conceptualized model that consists of several segments with connecting rotational springs is capable of describing the controlling failure mechanisms of stiffened plates under various corrosion scenarios. On this basis, for the purpose of the identification of the failure modes of pitting corroded steel stiffened plates, a relative cross section loss factor is proposed and validated by a large number of the tested and simulated cases.

Nondestructive Evaluation of Rebar Corrosion–Induced Damage in Concrete through Ultrasonic Imaging

AbstractCorrosion of reinforcement in concrete is a billion dollar problem spread across the globe. Early detection of corrosion-induced damage preempts weakening of the structure and timely rehabi...

A Two-Year Evaluation of Corrosion-Induced Damage to Hot Galvanized Reinforcing Steel B500SP in Chloride Contaminated Concrete.

Corrosion-induced damage to concrete reinforced with bars is a serious problem regarding technical and economic aspects and strongly depends on used materials, corrosion environment, and service life. Tests described in this paper refer to a two-year evaluation of the effectiveness of protection provided by zinc-coated low-carbon reinforcing steel of grade B500SP in concrete against chloride corrosion. Performed tests were comparative and included measurements conducted on four groups of concrete test elements with dimensions of 40 mm × 40 mm × 140 mm reinforced with a bar having a diameter of ϕ8 mm. Particular groups were a combination of different types of concrete with or without chloride additives, with galvanized or black steel. Chlorides as CaCl2 were added to the concrete mix in the amount of 3% of cement weight in concrete. Reinforced concrete specimens were periodically monitored within two years using the following techniques: linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Polarization measurements were conducted in a three-electrode arrangement, in which a rebar in concrete served as a working electrode, stainless steel sheet was used as an auxiliary electrode, and Cl−/AgCl,Ag was a reference electrode. Comparative tests of changes in the density of corrosion current in concrete specimens without chloride additives basically demonstrated no development of corrosion, and possible passivation was expected in case of black steel. Higher densities of corrosion current were observed for galvanized steel during first days of testing. The reason was the dissolution of zinc after the contact with initially high pH of concrete pore solution. Six-month measurements demonstrated a higher density of corrosion current in concrete specimens with high concentration of chlorides, which unambiguously indicated corrosion in concrete reinforced with galvanized or black steel. Densities of corrosion current determined for selected specimens dramatically decreased after an 18-month interval in measurements. Corrosion was even inhibited on black steel as an insulating barrier of corrosion products was formed. The above observations were confirmed with structural studies using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. Results obtained from corrosion (LPR, EIS) and structural (SEM, EDS) tests on specimens of concrete reinforced with steel B500SP demonstrated a very favorable impact of zinc coating on steel by providing two-year protection against corrosion in the environment with very high chloride content.

Nonlinear vibration-based estimation of corrosion-induced deterioration in reinforced concrete

The structural integrity of corroded reinforced concrete (RC) elements is commonly evaluated by the electrical resistivity method to estimate only the mass loss of reinforcement. It is also possible to evaluate overall deterioration induced by corrosion in the RC elements by examining their nonlinear dynamic behaviors. Therefore, herein, a nonlinear vibration-based diagnostic technique is investigated to measure the magnitudes of higher harmonics of resonance caused due to the corrosion-induced damage in the reinforced concrete. The developed diagnostic technique utilizes an adaptive higher order spectral analysis, which incorporates the wavelet transform instead of the Fourier transform, in order to suit the transit vibration signals generated under an impact hammer. Initially, the algorithm to extract a diagnostic feature, named the wavelet transform-based bicoherence (WTB), is developed on the synthetic vibration signals with different levels of nonlinearity. Then, the developed diagnostic method is demonstrated on two lab-scale RC columns. Comparison of the results obtained by the traditional Fourier-based and the proposed wavelet-based bispectra reveals up to 42.7% improvement in the discrimination of the damaged column from the intact one.

Empirical models of corrosion rate prediction of steel in reinforced concrete structures

Corrosion rate is one of the most important input parameters in corrosion-induced damage prediction models as well as in calculation of service-life for reinforced concrete structures. In most cases, instantaneous measurements or constant corrosion rate values used in damage prediction models is irrelevant. The new factors appearing such as corrosion-induced cover cracking, concrete quality to change the corrosion rate should be taken into consideration. This study shows several empirical models to predict the corrosion rate and their limits of application. The predicted values of steel corrosion rate using four empirical models are compared with the measured values of a series of 55 experimental samples collected from the literature. The results show that the empirical models overestimated the experimental corrosion rate. Using model proposed by Liu and Weyers provided the best agreement with the experimental data.
 Keywords:
 corrosion rate; prediction model; reinforced concrete; chloride ions; reinforcement corrosion.

Bond characteristics of corroded pullout specimens exposed to elevated temperatures

This paper presents an experimental study carried out to examine the extent of deterioration of bond properties of super ductile (SD) TMT reinforcing steel bars with normal strength concrete on account of exposure to multiple combinations of corrosion-induced damage in terms of mass loss and exposure to elevated temperatures. The study involved an experimental evaluation of bond properties and behavior of corroded pullout specimens exposed to elevated temperatures. RILEM specified Pullout specimens with centrally placed rebars of various sizes were exposed to impressed current accelerated corrosion to achieve desired levels of corrosion in terms of percent mass loss of (2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, and 18%, etc.). and then to temperatures targeted at (200 °C, 400 °C, 500 °C, 600 °C, 700 °C & 800 °C). The corroded and subsequently heated pull out bond specimens were tested to failure in pull-out mode using displacement controlled UTM to investigate the residual bond strength and bond-slip behavior. The slip of the rebar, at the loaded as well as the unloaded end, was recorded through a set of linear variable displacement transducers (LVDT) arrangement mounted to the projected reinforcing bar on each side of the specimen. The study presents unique bond-slip response curves depicting the overall behavior of the bond mechanism. The results indicate a notable reduction in bond strength as well as the bond-slip response of pullout specimens on account of the superimposition of the two phenomena. A detailed account of the test results, analysis and discussion has been presented. The findings of this study have direct implications on procedures used for predicting the ultimate behavior of aged or corroded structural elements exposed to an accidental fire. A trend of deteriorations has been established for all research variables and a model best fitting the experimental data has been proposed in terms of a regression correlation.

Localized corrosion induced damage monitoring of large-scale RC piles using acoustic emission technique in the marine environment

An experimental study was conducted to apply the acoustic emission (AE) technique to monitor the corrosion process and cracking behavior in large-scale reinforced concrete (RC) pile specimens. In this study, the underwater and tidal zones of six RC piles were exposed to accelerated, localized corrosion in a simulated marine environment to reach 5%, 10% and 20% steel mass loss. The two piles with 20% steel mass loss together with another reference pile without corrosion were continuously monitored during the test via three attached AE sensors. Tidal action had a significant impact on the AE signals; accordingly, a novel amplitude-duration-peak frequency-based AE signal filter (ADPF) was proposed, which achieved better performance than the previous amplitude-duration-based filters. Additionally, the conjoint analysis of AE signals and the fractal dimension of cover cracks throughout the corrosion period enabled global detection of localized corrosion-induced damage of piles, regardless of sensor location. This study also presents an integrated corrosion-induced damage detection framework and four models based on multi-layer perception (MLP) networks to predict the corrosion level of the underwater and tidal zones of piles in the marine environment.

Simulation of the mechanical behavior of pre-corroded AA2024-T3 specimens with equivalent surface notches

The present work aims to numerically simulate the mechanical tensile behaviour of AA2024-T3 specimens with pre-existing corrosion-induced surface damage. The concept lies on the calculation of an equivalent artificial-machined surface notch that decreases the tensile mechanical properties degradation with the same manner as the corrosion exposure. Recently, in Alexopoulos et al. (2019) an experimental effort for the physical correlation of the mechanical properties’ degradation due to artificially machined surface notches with corrosion-induced damage was attempted. In the present work, a finite element model (FEM) was developed to simulate the tensile mechanical behaviour of the already notched tensile specimens. The model was validated by the experiments and a satisfactory correlation between the numerically obtained and the experimental results for both, yield stress Rp and elongation at fracture Af was achieved. Essential decrease in Af (approximately 50% of the initial value) was observed even for the low notch depth of 0.15 mm while this was not the case for yield stress. Furthermore, it was observed that the morphology of the developed plastic zones changes drastically for notch depths higher than 0.60 mm, in good correlation with experimental observations, according to which increased notch depths induce generalized yielding conditions for lower stress/strain values.

Evaluation of ultimate capacity of corrosion damaged reinforced concrete beam-columns using nonlinear sectional analysis

A simplified nonlinear sectional analysis approach (NLSA) of aged reinforced concrete beam-columns based on numerical integration, enhanced inspection, material testing and/or empirical estimation of materials deterioration due to reinforcement corrosion is proposed. The proposed procedure is an iterative nonlinear technique that uses numerical integration of the sectional stresses and satisfies force equilibrium in every load increment step. The NLSA model incorporates corrosion-induced damage by reducing the steel cross section and ductility, removing the loss of concrete cover, and accounting for the loss of local bond in corrosion-damaged zones. Two case studies are presented to estimate the effects of corrosion on the structural behaviour of reinforced concrete beam-columns by taking into account critical damage states. The model results show good agreement with test results, high numerical stability and consistent convergence for all examined loading cases.

An equivalent smeared layer method for simulating the non-uniform corrosion-induced damage of concrete

The numerical prediction of concrete damage caused by corrosion-induced expansion of steel reinforcement has been seriously plagued by two problems: (1) the thickness of rust layer is zero before corrosion, but it is difficult to set elements whose size increases from zero to a non-zero value; and (2) the large difference between the sizes of rust, steel reinforcement and concrete elements can cause serious accuracy defects. To solve the above problems, this paper presents a new equivalent smeared layer model. In this approach, the outer portion of the steel reinforcement is reset as the hypothetical deformable material whose elastic modulus depends on the degree of corrosion. Then, a specific numerical module is developed to predict the entire process of concrete cracking. The simulation under the uniform, 2D non-uniform and 3D pitting corrosion all can be carried out. Several sets of data are compared with the numerical results to verify the proposed model. Two illustrative examples indicate that it is very suitable for actual application.

Simulation of the corrosion-induced damage on aluminum alloy 2024 specimens with equivalent surface notches

Simulation of the corrosion-induced damage on aluminum alloy 2024 specimens with equivalent surface notches

Effect of time dependent corrosion rate on residual capacity of corroded RC beam

Corrosion is the most commonly severe defect in reinforced concrete (RC) structures and it mainly causes reduced rebar cross-section. The corrosion rate is the determining parameter of the progress of corrosion-induced damage. The present work is focused on the application of finite element (FE) analysis, using DIANA, to predict the residual capacity of reinforced concrete beam with different degree of corrosion. To this aim, existing experimental data is used to develop a FE model of corroded beams and to investigate their behaviour. This model is validated to predict the impact of time and current rate of corrosion on the residual load carrying capacity of corroded RC beams.

Corrosion-Induced Damage and Residual Strength of WC-Co,Ni Cemented Carbides: Influence of Microstructure and Corrosion Medium

The corrosion behavior of cemented carbides with binders of different chemical nature (Co and Ni) and carbides with distinct mean grain size (ultrafine and coarse) was studied. The investigation also included corrosion media (acidic and neutral solutions containing chlorides and an alkaline solution) as experimental variables. Immersion tests were performed to induce corrosion damage in a controlled way. Electrochemical parameters were measured together with a detailed inspection of the corroded surfaces. Microstructural influence on the tolerance to corrosion damage was evaluated in terms of residual strength. Results pointed out that corrosion rates were lower in the alkaline solution. In contrast, acidic media led to higher corrosion rates, especially for cemented carbides with Co regardless the influence of carbide mean grain size. Corrosion damage resulted in strength degradation due to the formation of surface corrosion pits in acidic solution. In neutral and alkaline solutions, much less pronounced effects were determined. Focused Ion Beam (FIB)/ Field Emission Scanning Electron Microscopy (FESEM) results revealed differences in corrosion-induced damage scenario. In acidic solution, corrosion starts at binder pool centers and evolves towards binder/WC interfaces. Meanwhile, corrosion in alkaline solution is initially located at binder/WC interfaces, and subsequently expands into the ceramic particles, developing a microcrack network inside this phase.

AE Monitoring Corrosion-induced Deterioration of Reinforced Concrete Piles in The Simulated Marine Environment

An experiment study was conducted to assess the effectiveness of acoustic emission (AE) technique monitoring the corrosion-induced damage in the marine environment. Three reinforced concrete (RC) piles of 1600 mm long by 200 mm square were casted and then were exposed in a simulated marine environment to reach 5%, 10% and 20% of steel rebar mass loss respectively. Throughout the whole test period, all specimen was monitored by three AE sensors installed at two different heights of the concrete surface and at the end of the steel rebar, respectively. The AE activities were analyzed to determine corrosion-induced dterioration at different corrosion levels. Based on the finding, the effectiveness of AE technique on monitoring of RC piles of high-pile under aggressive marine environmental conditions was established.

Simulation of the corrosion-induced damage on aluminum alloy 2024 specimens with equivalent surface notches

The effect of corrosion environment aggressiveness on the tensile mechanical properties degradation of AA2024-T3 was investigated. Tensile speci­­mens were pre-corroded for various exposure times to different corrosive solutions, i.e., exfoliation corrosion (EXCO) and 3.5 wt. % NaCl. Then they were tested mechanically. In non-corroded specimens, surface notches of vari­ous depths were machined to simulate the de­gra­dation of the tensile mechanical properties due to the presence of artificial surface defects. A mechanical model was developed to correlate the corrosion-induced tensile ductility degradation due to pitting and possible hydrogen embrittle­ment with the equivalent arti­fici­al­ly induced surface notches. The cases studied for this physical cor­re­la­tion were: a) EXCO exposure with artificial notches, b) EXCO with 3.5 wt.% NaCl ex­posure and c) 3.5 wt.% NaCl ex­posure with artificial notches. Higher corre­la­tion was noticed for short exposure times for all cases where the dominant de­gradation mechanism is slight pitting form­ation. It was found that 1 h EXCO ex­­posure is equivalent to 92 h exposure to NaCl solution re­gard­ing the tensile duc­tility degradation while 24 h EXCO exposure has the same effect on duc­til­ity decrease with a 240 μm surface notch or 4000 h exposure to NaCl solution.