Mass Loss Of Steel Research Articles

Development of an Embedded UHF-RFID Corrosion Sensor for Monitoring Corrosion of Steel in Concrete

Corrosion of reinforcing steel is the leading cause of deterioration in concrete and impacts strongly the safety and durability of civil infrastructures. It occurs in marine environment with the presence of chloride which breaks the thin oxide film passivation layer leading to dissolution. This research proposes an innovative embedded sensor in concrete for the detection of corrosion of steel. The autonomous UHF RFID (Ultra High Frequency Radio Frequency Identification) sensor is based on the coupling between the antenna of a dipolar RFID tag and a layer of steel exposed to chloride in concrete. Variation of the RSSI (Received Signal Strength Indication) measured by the reader localized in air has two origins, namely the degree of moisture of concrete and the presence of the steel layer. By minimizing the impact of seawater ingress on the antenna property, the presence of metallic films of few micrometers thickness can be detected. This authorizes the development of the proposed method for monitoring mass loss of steel in concrete.

Phase-field simulations of cover cracking in corroded RC beams

Corrosion of steel reinforcement bars is a crucial issue for the reinforced concrete structures. Being one of the most common deterioration mechanisms, corrosion severely affects the serviceability and durability of the structure as the steel reinforcement suffers from a reduction of the cross section and deterioration of the mechanical properties. Additionally, due to the steel oxidation process, residual material is formed, and the volume occupied by the reinforcement increases, leading to cracking and spalling of the concrete cover. A predictive model coupling concrete carbonation process and phase-field approach for brittle fractures is proposed to simulate the carbonation induced corrosion of rebar and the subsequent cracking phenomenon. First, a Fick diffusion law is used to describe the carbon dioxide (CO2) diffusion within the concrete which leads to a generalized corrosion process. As the corrosion evolves, the steel mass loss is converted into expansion strain due to the formation of residual material, and the damage evolution within the concrete cover is determined. After validation against examples from the literature, numerical simulations are performed, presenting a phase-field strategy capable to describe the cover cracking of corroded RC beams.

Using high-performance cementitious mortar and external prestressing for retrofitting of corroded reinforced concrete beams

The effect of using high-performance polypropylene fiber–reinforced cementitious mortar on reinforced concrete beam repair was presented in this article. Results of an experimental study for the flexural performance of 13 reinforced concrete beams were presented. The corrosion level, in terms of the mass loss of steel, was estimated to be 10% and 15%. Three non-strengthened specimens were tested as a reference: one control uncorroded specimen and two control specimens corroded with 10% and 15%. Ten specimens were strengthened using different techniques; replacement of the spilled concrete at the tension zone with 40-mm-thick high-performance polypropylene fiber–reinforced cementitious mortar, using external prestressing bars at the tension zone with adding 20-mm-thick high-performance polypropylene fiber–reinforced cementitious mortar at the compression zone, and a combination of these techniques. The prestressing reinforcing bars stress was chosen to be 0.25 fpy and 0.38 fpy for the corroded 10% specimens and 0.25 fpy for the corroded 15% specimens. A combination of 40-mm-thick high-performance polypropylene fiber–reinforced cementitious mortar at the tension side and external prestressing bars at the tension zone increased the specimen capacity by 15% and 34% compared with the uncorroded and 10% corroded control specimens, respectively. A comparative study was conducted to evaluate the efficiency of various strengthening techniques. An analytical model was proposed in order to give design guidelines.

Time to cracking in concrete cover length due to reinforcement corrosion via a simplified fracture mechanics approach

Determination of the concrete cover cracking time is one of the main parameters in estimating service life of concrete structures exposed to chloride-laden and other aggressive environmental conditions. The corrosion of reinforcing steel embedded in concrete occurs as a result of chloride attack or carbonation, and thus the increase in the volume of corroded reinforcing steel cracks the cover. In this paper, a theoretical model is proposed to calculate the cracking initiation and propagation time within the concrete cover. Increase in the volume of corroded reinforcing bar induces an internal pressure on the concrete around the bar, which brings on the cracking initiation and propagation through the cover. The internal pressure caused by corrosion is expressed in terms of steel mass loss, and then Faraday's law is implemented to account for the time in relationships. The time corresponding to creation of the first crack is obtained based on crack opening definition, and the crack propagation is approximated on the basis of fracture mechanics relationships. The merit of using fracture mechanics is that the crack propagation time can be calculated thru any desired length of the cover. In this model, the time required for corrosion products to fill the porous zone between concrete and steel bar, as well as the time needed to fill the void within the crack are also accounted for. Validity of the proposed model is investigated via comparing the results achieved in this model with those of experiments published in the literature.

Relationship between steel mass loss and accelerated corrosion regimes in reinforced concrete columns

Present study aims to observe the consequence of varying the intensity of the accelerating impressed electrical current and situations of wetting-drying as hybrid accelerated corrosion regime on synthetically corroded concrete specimens, especially the loss of steel mass. Small-scaled reinforced concrete columns were fabricated and synthetically corroded by altered accelerating corrosion situations by applying an impressed current with intensity ranging between (50 and 500 μA/cm2). Moreover, the impressed current joined with two dissimilar durations of wetting-drying cycles for assessment. The steel mass losses during and at the end of the accelerated corrosion process were calculated, also, cracking configuration and damage shape were observed for accelerating corrosion. The outcomes designated that the hybrid method (impressed current joined with cycles of saline solution wetting and drying series) can be employed adequately to simulate the regular corrosion process in the reinforced concrete structure. The steel mass loss is mostly influenced by the intensities of the impressed accelerating current, while the crack appearance and the pattern of surface cracks, is influenced by wetting and drying cycles as well as the impressed accelerating current. Yet, increasing the current intensity produce a considerable growth in the cracking owing to the reinforcing steel corrosion in shorter stage.

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.

Determination of impressed current efficiency during accelerated corrosion of reinforcement

Impressed current technique is a widely adopted method for accelerating corrosion of steel reinforcement. The mass loss of steel can be theoretically estimated by Faraday's law with the assumption that all of the impressed current participated in the corrosion reaction. In the present study, accelerated corrosion process of reinforcing steel with impressed current was non-destructively traced by X-ray micro-computed tomography (μCT) with high accuracy. The mass loss of steel at different accelerated corrosion periods was analyzed and the efficiency of impressed current was calculated. It was found that the mass loss of steel did not always follow Faraday's law, and impressed current efficiencies varied with different corrosion periods. In the early corrosion periods, the water electrolysis occurred and lowered the current efficiency due to the high anode potential. While in the late corrosion periods, the natural corrosion caused the current efficiency to exceed 100%.

Development of Nano-SiO2 and Bentonite-Based Mortars for Corrosion Protection of Reinforcing Steel.

In this study, the use of nano-silica (nano-SiO2) and bentonite as mortar additives for combating reinforcement corrosion is reported. More specifically, these materials were used as additives in ordinary Portland cement (OPC)/fly ash blended mortars in different amounts. The effects of nano-silica and bentonite addition on compressive strength of mortars at different ages was tested. Accelerated corrosion testing was used to assess the corrosion resistance of reinforced mortar specimens containing different amounts of nano-silica and bentonite. It was found that the specimens containing nano-SiO2 not only had higher compressive strength, but also showed lower steel mass loss due to corrosion compared to reference specimens. However, this was accompanied by a small reduction in workability (for a constant water to binder ratio). Mortar mixtures with 4% of nano-silica were found to have optimal performance in terms of compressive strength and corrosion resistance. Control specimens (OPC/fly ash mortars without any additives) showed low early age strength and low corrosion resistance compared to specimens containing nano-SiO2 and bentonite. In addition, samples from selected mixtures were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Finally, the influence of Ca/Si ratio of the calcium silicate hydrate (C-S-H) in different specimens on the compressive strength is discussed. In general, the study showed that the addition of nano-silica (and to a lesser extent bentonite) can result in higher strength and corrosion resistance compared to control specimens. Furthermore, the addition of nano-SiO2 can be used to offset the negative effect of fly ash on early age strength development.

Effects of polypyrrole coated rebar on corrosion behavior of tunnel lining with the combination effect of sustained loading and pre-existing cracks when exposed to chlorides

This paper presents an experimental study on the mechanical behavior of a tunnel lining with pre-existing cracks that is subjected to accelerated corrosion. The surface strain, deflection, and load capacity of the concrete liner material were recorded, as well as the degree of rebar corrosion and the crack patterns that developed. The efficacy of the polypyrrole reinforcement coating in minimizing the effects of corrosion and the reinforcement effect on the physical properties of the concrete specimens were examined. The results show that both the pre-existing cracks and sustained loading have noticeable influence on the corrosion behavior of tunnel lining. The specimens with polypyrrole coating exhibited a delayed onset of reinforcement corrosion, less steel mass loss, smaller specimen surface strains and smaller transverse and longitudinal crack width.

Characteristic and Erosion Study of Uncoated Sand Proppant Using Impingement Test

The characterization and properties of sand from beaches in Malaysia that has potential to be used as proppant in hydraulic fracturing was investigated through impingement tests. Eight sand samples were obtained from eight different locations in Malaysia; three samples from West Coastal beaches (Selangor) and five from East Coastal beaches (Kelantan). These impingement tests were conducted by varying several parameters i.e. size ranges of sand, type of targeted metal and distance of nozzle standoff from target. In these tests, air was fed through an acrylic pipe with inner diameter of 8 mm and 4 m length at gas velocity of 100 m/s and flow rate of 200 l/min. 250 g of sand samples were fed in compressed air stream and the samples were projected toward targeted metal i.e. mild steel and aluminium with a 90° of impingement angle. These tests were conducted at different separation distance of 0.5, 2.5 and 5.0 inches of nozzle and target. The results were analysed by measuring the mass loss of the metals after impingement and the images of the impinged metals were captured using camera. The highest metal loss was obtained when the targeted metal was impacted with the largest size range of sand samples. The mass loss of mild steel ranged from 0.03 to 0.16 g and 0.10 to 0.22 g for aluminium, at a variable distance between the nozzle and metal target due to higher hardness of mild steel than aluminium. The mass loss reduced when the distance between nozzle and metal target increased due to energy loss because of the inter particle collision.

Effect of chloride ion on corrosion behavior of low carbon steel in 0.1 M NaHCO3 solution with different dissolved oxygen concentrations

The corrosion behavior of low carbon steel in 0.1 M NaHCO3 + 0.1 M NaCl solution with different dissolved oxygen concentrations was investigated with gravimetric tests and electrochemical measurements. Results show that the corrosion mass loss of steel is remarkably increased with the addition of chloride ion. In the initial stage, the carbon steel tends to active dissolution due to the dissolution effect of chloride ion on the oxide film; as a result, the corrosion potential maintains as low values. With the immersion time going by, the corrosion potential of the steel is promoted as a result of the accumulation of the corrosion products. However, the rust layer is loose and porous due to the deteriorating effect of chloride ion, which decreases the reduction resistance of oxygen. Meanwhile, the porous rust layer could be repaired by the depolarization of oxygen. Under the synergistic effect of chloride ion and oxygen, the corrosion of the steel is accelerated during the repeated process of dissolution and reparation of the oxide film.

Influence of matrix cracking and hybrid fiber reinforcement on the corrosion initiation and propagation behaviors of reinforced concrete

While fiber-reinforced concrete has been proposed for corrosion damage control of reinforced concrete, long-term behavior of these composites remains largely uninvestigated. In this study, reinforced concrete and reinforced hybrid fiber-reinforced concrete (HyFRC) were subjected to a chloride environment for 2.2 years. Samples were mechanically loaded prior to chloride exposure to induce varied matrix cracking characteristics. When precracked, the time to corrosion initiation is correlated to flexural stiffness degradation. After corrosion initiation, fiber reinforcement restricts corrosion-induced cracking, causes more extensive diffusion of corrosion products into the cementitious matrix, and lowers overall mass loss of steel reinforcing bars. The mechanical responses of corroded samples are also reported.

Post-repair flexural performance of corrosion-damaged beams rehabilitated with fabric-reinforced cementitious matrix (FRCM)

This paper presents the results of a research program examining the post-repair flexural response of corrosion-damaged reinforced concrete (RC) beams repaired with different FRCM systems. A total of nine RC beams were tested, including two beams that were neither corroded nor repaired, one beam that was corroded and not repaired, and six corroded-repaired beams that were prepared in two phases. Beams of phase I were subjected to an accelerated corrosion process for 210 days before being repaired whereas beams of phase II were initially subjected to accelerated corrosion for 70 days, then repaired and exposed to further corrosion for 140 days. Flexural test results showed that exposing the FRCM-repaired beams to corrosion after repair resulted in 23% reduction in steel mass loss. The use of U-shaped FRCM layers was more efficient in reducing the corrosion rate and increasing the ultimate strength of the repaired beams than the end-anchored FRCM layers. The PBO FRCM-repaired beams showed lower post-yielding stiffness and more ductility at failure than those of their carbon FRCM-repaired counterparts. Beams that experienced post-repair corrosive environment showed load-carrying capacities that ranged between 14 and 65% above those of the virgin beam. ACI 549.4R-13 provisions conservatively predict the ultimate capacities of the FRCM-repaired beams exposed to post-repair corrosive environment.

Utilization of Electrolytic Manganese Dioxide (E.M.D.) waste in concrete exposed to salt crystallization

In the present study, the physico-mechanical properties and corrosion resistance of reinforced concrete containing Electrolytic Manganese Dioxide (E.M.D.) waste were investigated. Concrete samples prepared in the lab with and without the use of EMD waste were exposed to sulfate and chloride salt solutions. In particular, the test samples were placed in 5% w/w Na2SO4 solution, while chloride penetration resistance was studied in 3.5% w/w NaCl solution. The concrete mixtures were prepared with 0%, 5% and 10% w/w replacement of Ordinary Portland Cement (OPC) with the aforementioned waste additive. For testing, specimens of varying shapes and dimensions were cast; cylindrical reinforced cement mortar specimens were also prepared. Tests for estimating the physico-mechanical properties (compressive strength, modulus of elasticity, porosity and sorptivity), mass loss of steel and thermal response of concrete (DTA/TG) were performed; the carbonation depth of mortars exposed to atmospheric conditions was also estimated. The experimental results generally suggest that the EMD waste additive does not affect negatively the properties of concrete partially immersed in chloride salt solution; in addition, the anticorrosive effect of EMD waste on steel rebars embedded in cement mortars was also observed. On the other hand, the composite concretes immersed in sulfate salt solution exhibited inferior values for all measured properties.

Analytical assessment of the bearing capacity of RC beams with corroded steel bars beyond concrete cover cracking

Abstract Corrosion of steel reinforcement is one of the major causes that limit durability and serviceability performance of reinforced concrete (RC) structures. This paper reviews thoroughly available experiments and analytical approaches in the relevant international literature and introduces a calculation model for assessing steel bar mass loss and contributes to further utilization of common in-situ inspections from a structural point of view. The model is based on the width of longitudinal crack of concrete cover, as a function of cover depth, bar diameter and mechanical properties of concrete. The model includes the well-known relationships for the steel mass loss during the first phase of rust formulation, filling the porous zone as well as during the phase that the radial pressure exceeds the concrete strength and causes cover cracking. The assumption followed herein for the flexibility of cracked concrete allows for the estimation of steel bar corrosion rate even beyond concrete cover cracking, by visual mapping of the width of longitudinal cracks. Then, the corresponding flexural capacity of the beams at yield and at maximum may be assessed. The predictions of the model are validated against 51 non-strengthened corroded beams and 24 strengthened corroded beams with Fiber Reinforced Polymer (FRP) materials published in the international literature.

Corrosion Activity on CFRP-Strengthened RC Piles of High-Pile Wharf in a Simulated Marine Environment

We report test results from an experimental study to investigate the effectiveness of carbon fiber-reinforced polymer (CFRP) against reinforcing steel bar corrosion. Twelve reinforced-concrete pile specimens of 180 mm square by 1,600 mm long were cast. Three pile specimens were corroded to 5% steel mass loss and then strengthened with CFRP sheets; four specimens were strengthened by using CFRP sheets, whereas the remaining five specimens were not strengthened. The specimens were placed in a simulated marine environment, and corrosion was induced by an impressed current technique. At different theoretical corrosion degrees, nondestructive tests were performed to investigate the corrosion activity of the pile specimens, and destructive tests were performed to determine reinforcing steel bar mass loss. Based on the findings, the effectiveness of the CFRP-strengthened RC piles under aggressive marine environmental conditions was established.

Application of acoustic emission monitoring for assessment of bond performance of corroded reinforced concrete beams

This article presents the results of an experimental investigation on the application of acoustic emission monitoring for the evaluation of bond behaviour of deteriorated reinforced concrete beams. Five reinforced concrete beam–anchorage specimens designed to undergo bond failure were exposed to corrosion at one of the anchorage zones by accelerated corrosion. Two additional beams without exposure to corrosion were included as reference specimens. The corroded beams were subjected to four variable periods of corrosion, leading to four levels of steel mass loss (5%, 10%, 20% and 30%). After these corrosion periods, all seven beams were tested to assess their bond performance using a four-point load setup. The beams were continuously monitored by attached acoustic emission sensors throughout the four-point load test until bond failure. The analysis of acquired acoustic emission signals from bond testing was performed to detect early stages of bond damage. Further analysis was executed on signal strength of acoustic emission signals, which used cumulative signal strength, historic index (H(t)) and severity (Sr) to characterize the bond degradation in all beams. This analysis allowed early identification of three stages of damage, namely, first crack, initial slip and anchorage cracking, before their visual observation, irrespective of corrosion level or sensor location. Higher corrosion levels yielded significant reduction in both bond strength and corresponding acoustic emission parameters. The results of acoustic emission parameters (H(t) and Sr) enabled the development of a damage classification chart to identify different stages of bond deterioration.

The Use of Acoustic Emission Intensity Analysis for the Assessment of Cover Crack Growth in Corroded Concrete Structures

In this paper, acoustic emission (AE) intensity analysis was utilized to assess the concrete cover cracking due to steel corrosion in reinforced concrete structures. A total of 30 reinforced concrete prism samples were tested under an accelerated corrosion test coupled with continuous AE monitoring using attached AE sensors. The samples were cast with three concrete cover thicknesses (20, 30 and 40 mm) around steel bars and were exposed to five percentages of steel mass loss: 1, 2, 3, 4, and 5 %. The cover cracking was monitored daily by visual inspection to detect and measure crack widths. Different AE signal parameters were continuously recorded during the tests, including number of hits, signal strength, energy, and amplitude. The acquired AE events were subjected to an intensity analysis of signal strength to estimate historic index (H (t)) and severity (\(S_r)\). In addition, a b value analysis was conducted on all AE data and the results were compared to those obtained from the intensity analysis. The results showed that increasing the cover thickness had no significant impact on AE parameters (number of hits, cumulative signal strength, cumulative energy, amplitude, H (t), and \(S_{r})\) at similar values of crack growth. Nonetheless, varying the cover thickness from 20 to 40 mm resulted in lower crack widths and slightly higher b values at the same levels of steel mass loss. It was also found that both H (t) and \(S_r\) showed a more evident correlation with the values of crack growth than did b values, regardless of cover thickness or percentage of steel mass loss. Finally, an intensity classification chart was developed to quantify the cover crack growth based on the values of H (t) and \(S_{r}\).

Effect of Cr on Characteristic of Rust Layer Formed on Low Alloy Steel in Flow-accelerated Corrosion Environment

The flow-accelerated corrosion experiments were carried out to research the effect of Cr on the rust layers formed on the carbon steel and Cr-containing steel, as well as the structure of rust layer of the two experimental steels. The influence of Cr on the flow-accelerated corrosion resistance and the corrosion morphology of inner rust layer formed on the Cr-containing steel were studied by the methods of polarization curves, scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscope. The distribution of Cr and its form of existence in the inner rust layer were analyzed. The results show that corroded mass loss of Cr-containing steel is lower than that of carbon steel and its inner rust layer is compact. Cr exists in the form of Fe2CrO4 and is enriched in the inner rust layer. This concentration could make the inner rust layer exhibit the tendency of amorphous. This phenomenon is related to fine Fe2CrO4. The inner rust layer becomes more compact because of the formation of fine Fe2CrO4, and the protectiveness of inner rust layer could be improved remarkably.

Tribocorrosion behaviour of type S31254 steel in seawater: Identification of corrosion–wear components and effect of potential

Tribocorrosion is an irreversible transformation of materials and often causes the premature failure of engineering components. In this work, the tribocorrosion behaviour of S31254 steel was investigated on a pin-on-disc tribometer at 50 N, 0.24 m s−1. In seawater, there existed a synergy between corrosion and wear, and this synergy was controlled by potentials through deteriorating the characteristics of the contact surfaces. Especially at +0.3 V, pitting corrosion occurred on metal surface, and the generated pits became the preferred locations of wear and tear, leading to a great synergy and accelerated materials loss rate. Combining X-ray microanalysis with the morphologies of the contact surfaces, the features of abrasive wear, adhesive wear, delamination and plastic deformation were revealed. Quantitative analysis shows that mechanical and corrosion-accelerated wear determined the total mass loss of S31254 steel during tribocorrosion at different potentials.