Materials

Research

17 pages, 5531 KiB

Open AccessArticle

Effect of Imidazoline Inhibitor on the Rehabilitation of Reinforced Concrete with Electromigration Method

by Chonggen Pan, Jianghong Mao and Weiliang Jin

Materials 2020, 13(2), 398; https://doi.org/10.3390/ma13020398 - 15 Jan 2020

Cited by 7 | Viewed by 2130

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of [...] Read more.

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of the steel bar under the action of an electric field. During the migration process, a higher ionization capacity of the inhibitor with a symmetrical molecular structure was introduced. A new imidazoline inhibitor was, therefore, employed in this study due to its great ionization capacity. The effect of imidazoline and triethylenetetramine inhibitor on chloride migration, corrosion potential, and strength of concrete were explored. The research results showed that the effect of chloride extraction and electrochemical chloride extraction made no significant difference on the surface of the concrete, where chloride extraction efficiency was more than 70%, and the chloride extraction efficiency was more than 90% around the location of the steel. while a dry-wet cycle test, the potential of concrete increased by about 200 mV by mixing imidazoline inhibitor. The imidazoline inhibitor was found to be effective at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete’s strength. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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19 pages, 4038 KiB

Open AccessArticle

An Investigation on the Usability of Acceleration Test by Impressed Anodic Current for Evaluating Corrosion Behavior of Hot-Dip Galvanized Rebar in Concrete

by Hong-bok Choe, Yuhei Nishio and Manabu Kanematsu

Materials 2019, 12(21), 3566; https://doi.org/10.3390/ma12213566 - 30 Oct 2019

Cited by 2 | Viewed by 2011

Abstract

Hot-dip Galvanized rebar (hereafter, HDG rebar) has an anti-corrosion effect due to the sacrificial anodic reaction of zinc. Additionally, the zinc coating itself provides barrier protection for the steel substrate. Meanwhile, from one of the investigations on the field performance of HDG rebar [...] Read more.

Hot-dip Galvanized rebar (hereafter, HDG rebar) has an anti-corrosion effect due to the sacrificial anodic reaction of zinc. Additionally, the zinc coating itself provides barrier protection for the steel substrate. Meanwhile, from one of the investigations on the field performance of HDG rebar in concrete, HDG rebar did not protect the substrate when the remaining zinc was under 50 µm. For the evaluation of this property over a short period of time, an acceleration test using impressed anodic current (hereafter, acceleration test) may be useful. This test impresses constant direct current into the rebar and can result in the intended quantitative extent of the anodic reaction. However, in using this test on HDG rebar, it was found that the high rate of applied current density could cause an unintended early end of the anti-corrosion effect of zinc, despite there being more than 50 µm of remaining zinc thickness. In this study, the usability of the acceleration test was investigated to determine if it is a suitable method for evaluating the anti-corrosion behavior of HDG rebar in concrete. As a test variable, a comparatively low rate of applied current density was used in the experiments. As a result, it was clarified that an effective corrosion protection of the substrate was made with an increase of the zinc corrosion amount. This anti-corrosion effect was similar to that known to exist in actual corrosion environments. This behavior was terminated when the concrete cracked, and the substrate became corroded. While the test condition in this study resulted in an early end of the anti-corrosion effect of zinc, a linear correlation was achieved between the applied current density and the remaining zinc thickness at the time that the anti-corrosion effect was terminated. It was found that lowering the applied current density resulted in a more suitable test condition. In conclusion, the acceleration test was found to be useful, although further experimental validation is necessary to confirm this finding. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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18 pages, 3927 KiB

Open AccessArticle

Experimental Study on Bond-Slip Behavior between Corroded I-Shaped Steel and Concrete in Subsea Tunnel

by Mingnian Wang, Yiteng Zhang, Li Yu, Yucang Dong, Yuan Tian and Guojun Zhou

Materials 2019, 12(18), 2863; https://doi.org/10.3390/ma12182863 - 05 Sep 2019

Cited by 9 | Viewed by 2277

Abstract

Degradation of the bond between I-shaped steel and concrete due to the corrosion of I-shaped steel significantly affects the durability of steel reinforced concrete (SRC) structures. This study carried out the accelerated corrosion test and push-out test to study the bond-slip behavior and [...] Read more.

Degradation of the bond between I-shaped steel and concrete due to the corrosion of I-shaped steel significantly affects the durability of steel reinforced concrete (SRC) structures. This study carried out the accelerated corrosion test and push-out test to study the bond-slip behavior and characteristics considering the corrosion of I-shaped steel, and test results indicated that: (1) The performance degradation of the bond-slip accelerated when the corrosion ratio reached 12%. (2) The corrosion failure pattern of SRC experienced slip phase and destruction phase in the rising stage. (3) Based on the principle of minimum potential energy, the bond stress was obtained only with the load and the displacement in the free end and the loading end. (4) Meanwhile, a new bond-slip degradation model was developed using the interface damage theory. Finally, the proposed model agreed with the experimental results. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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20 pages, 8180 KiB

Open AccessArticle

Influence of Pore Networking and Electric Current Density on the Crack Pattern in Reinforced Concrete Test Due to Pressure Rust Layer at Early Ages of an Accelerated Corrosion Test

by Ángela M. Bazán, Encarnación Reyes and Jaime C. Gálvez

Materials 2019, 12(15), 2477; https://doi.org/10.3390/ma12152477 - 04 Aug 2019

Cited by 4 | Viewed by 3930

Abstract

Research on early stages of corrosion of steel bars caused by chloride penetration is relevant in improving the durability of reinforced concrete structures. Similarly, the formation and development of cracks induced in the surrounding concrete is also of great importance. This paper uses [...] Read more.

Research on early stages of corrosion of steel bars caused by chloride penetration is relevant in improving the durability of reinforced concrete structures. Similarly, the formation and development of cracks induced in the surrounding concrete is also of great importance. This paper uses integration of the analytical models examined in the published literature, combined with experimental research in corrosion induced at the concrete/steel interface, in estimating the time-to-crack initiation of reinforced concrete subjected to corrosion. This work studies the influence of the porous network and electric current density on the cracking process at early ages. The experimental program was performed by using an accelerated corrosion test. Two types of concrete were performed: A conventional concrete (CC) and a concrete with silica fume (SFC). A current density of 50 μA/cm² and 100 μA/cm² was applied to specimens of both concretes. Examination performed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) provided both qualitative and quantitative information on the penetration of the rust layer in the surrounding concrete porous network. Strain gauges were used to measure corrosion-induced deformations between steel and concrete matrices, as well as the formation of corrosion-induced cracks. A good correlation between the rate of penetration of the rust products in the surrounding pores and the delay of the cracking pressure in concrete was observed from the experimental results. This phenomenon is incorporated into the analytical model by using a reduction factor, which mainly depends on the pore size of the concrete. The crack width obtained exhibited a significant dependency on electric current density at the beginning of the test, depending mainly on the pore size of the concrete later. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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17 pages, 9600 KiB

Open AccessArticle

Effect of the Electric Field on the Distribution Law of Chloride Ions and Microstructure in Concrete with the Addition of Mineral Admixtures

by Xiaoli Xie, Qingge Feng, Zheng Chen and Wei Lu

Materials 2019, 12(9), 1380; https://doi.org/10.3390/ma12091380 - 28 Apr 2019

Cited by 4 | Viewed by 2520

Abstract

Migration testing of chloride under an electric field is a fast and effective method to determine the corrosion resistance of reinforced concrete against chloride. In this study, a series of admixture-involved (fly ash and slag) concrete specimens were produced for an accelerating chloride [...] Read more.

Migration testing of chloride under an electric field is a fast and effective method to determine the corrosion resistance of reinforced concrete against chloride. In this study, a series of admixture-involved (fly ash and slag) concrete specimens were produced for an accelerating chloride diffusion test in 3% NaCl solution under an electric field and natural chloride diffusion in 165 g/L NaCl solution under immersion conditions. Then, the chloride profile and pore structure of concretes aged 56 and 91 days were compared to investigate the effect of the electric field on chloride diffusion as well as the microstructure of the concrete. The results showed that, under accelerating electric field conditions, the degree to which chloride refined the internal pore structure of the concrete was weaker than that under natural immersion conditions. The applied electric field changed the pore structure inside the concrete, but it had little effect on the distribution of total, free, and bound chlorides and their mutual relationship. In addition, it is necessary to consider that the electric field effect on chloride migration varies with the concrete mix proportions. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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14 pages, 6396 KiB

Open AccessArticle

Rebar Corrosion Investigation in Rubber Aggregate Concrete via the Chloride Electro-Accelerated Test

by Jian Liang, Han Zhu, Lei Chen, Xiaobin Han, Qinglin Guo, Ying Gao and Chunsheng Liu

Materials 2019, 12(6), 862; https://doi.org/10.3390/ma12060862 - 14 Mar 2019

Cited by 28 | Viewed by 3368

Abstract

Erosion effect of chloride ions from the marine, deicing salt, saline-alkali land and some industrial environments will cause the corrosion of rebar in concrete, which is one of the most harmful factors affecting the durability of concrete structure. It had been proved that [...] Read more.

Erosion effect of chloride ions from the marine, deicing salt, saline-alkali land and some industrial environments will cause the corrosion of rebar in concrete, which is one of the most harmful factors affecting the durability of concrete structure. It had been proved that the incorporation of rubber aggregates increase the capillary saturation of cement concrete and reduce the corrosion degree of rebar. This paper investigated the rebar corrosion behavior in rubber aggregate concrete under the chloride electro-accelerated corrosion condition and such an investigation has not been seen in any public literature. Two water-cement ratios (0.45 and 0.55) and four rubber contents (0, 50, 100, and 150 kg/m³) were selected for experiment. Four-point bending tests of concrete beam were conducted before and after chloride ion erosion in order to determine effect of rubber aggregate on the durability of rebar. Results showed that rebar corrosion degree decreased with the increase of rubber aggregate in concrete. Besides, the more the dosage of rubber is, the better the anti-crack performance of cement concrete. This will postpone the crack development and reduce the peak of rebar corrosion. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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19 pages, 6246 KiB

Open AccessArticle

Experimental Study on Shear Capacity of Reinforced Concrete Beams with Corroded Longitudinal Reinforcement

by Sun-Jin Han, Hyo-Eun Joo, Seung-Ho Choi, Inwook Heo, Kang Su Kim and Soo-Yeon Seo

Materials 2019, 12(5), 837; https://doi.org/10.3390/ma12050837 - 12 Mar 2019

Cited by 9 | Viewed by 3028

Abstract

In this study, shear tests were conducted to investigate the effects of longitudinal reinforcement corrosion on the shear capacity of reinforced concrete (RC) members with transverse reinforcement. To this end, a total of eight test specimens were fabricated, and the corrosion rates and [...] Read more.

In this study, shear tests were conducted to investigate the effects of longitudinal reinforcement corrosion on the shear capacity of reinforced concrete (RC) members with transverse reinforcement. To this end, a total of eight test specimens were fabricated, and the corrosion rates and anchorage details of rebars were set as test variables. In addition, an accelerated corrosion technique was used to introduce corrosion into the longitudinal reinforcement without corroding shear reinforcement. The test results indicated that the capacities of the specimens in which tension reinforcement was not properly anchored at the ends of the members decreased rapidly at high corrosion rates, whereas the capacities of the specimens in which tension reinforcement was properly anchored by hooks were similar to or higher than those of the non-corroded specimens, despite bond loss caused by corrosion. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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12 pages, 11481 KiB

Open AccessArticle

Use of Non-Linear Ultrasonic Techniques to Detect Cracks Due to Steel Corrosion in Reinforced Concrete Structures

by Miguel Ángel Climent, Marina Miró, Jesús Carbajo, Pedro Poveda, Guillem de Vera and Jaime Ramis

Materials 2019, 12(5), 813; https://doi.org/10.3390/ma12050813 - 09 Mar 2019

Cited by 30 | Viewed by 4003

Abstract

In this work, non-linear ultrasonic wave techniques have been used to detect the onset of micro-cracking due to steel corrosion in model reinforced concrete elements. The specimens were of prismatic shape with a single steel rebar. The corrosion was forced by admixing an [...] Read more.

In this work, non-linear ultrasonic wave techniques have been used to detect the onset of micro-cracking due to steel corrosion in model reinforced concrete elements. The specimens were of prismatic shape with a single steel rebar. The corrosion was forced by admixing an appropriate amount of sodium chloride at the moment of preparing the concrete mix, and by the application of an electric field, using a constant current density power source, and making the steel rebar work as the anode, and an external counter-electrode as the cathode. The preliminary results indicate that the onset of cracking seems to be accompanied by the appearance of higher-harmonic generation at the output signal (harmonic distortion), when the system is excited by the means of an ultrasound wave with a burst central frequency. Other phenomena related to the micro-cracks induced by corrosion, such is the parametric generation with respect to the fundamental amplitude, have not been observed until now. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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13 pages, 7337 KiB

Open AccessFeature PaperArticle

Effect of Vietnamese Fly Ash on Selected Physical Properties, Durability and Probability of Corrosion of Steel in Concrete

by Chinh Van Nguyen, Paul Lambert and Quang Hung Tran

Materials 2019, 12(4), 593; https://doi.org/10.3390/ma12040593 - 16 Feb 2019

Cited by 17 | Viewed by 4771

Abstract

Vietnamese fly ash was used as a partial replacement for ordinary Portland cement in the proportions of 10%, 20% and 40%, while the water to cementitious ratios were kept constant at 0.42, 0.5 and 0.55, respectively, for three groups. The compressive strengths of [...] Read more.

Vietnamese fly ash was used as a partial replacement for ordinary Portland cement in the proportions of 10%, 20% and 40%, while the water to cementitious ratios were kept constant at 0.42, 0.5 and 0.55, respectively, for three groups. The compressive strengths of all mixes were determined up to 90 days. The acid resistance of fly ash concrete was examined by the mass loss and compressive strength loss of 100 × 100 × 100 mm³ cubes immersed in a 10% H₂SO₄ solution. The probability of steel corrosion in the fly ash concrete was assessed by measuring the half-cell potentials of steel bars within beams dimensions of 100 × 100 × 500 mm³, and the flexural strengths of these beams after 300 days of immersion in a 5% NaCl solution were determined. The results demonstrate that the compressive strength of fly ash concrete is reduced at an early age but increases as the concrete continues to hydrate. The fly ash increases the sulfuric acid resistance of concrete. Fly ash additions have only a limited effect on reducing the risk of probability of corrosion of steel in the concrete. The load capacities of 10% and 20% fly ash reinforced concrete beams are higher than that of the control beams after 300 days immersed in a 5% NaCl solution. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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10 pages, 4548 KiB

Open AccessArticle

Corrosion Investigation of Reinforced Concrete Based on Piezoelectric Smart Materials

by Weihua Shi, Ying Chen, Peng Liu and Dongyu Xu

Materials 2019, 12(3), 519; https://doi.org/10.3390/ma12030519 - 09 Feb 2019

Cited by 7 | Viewed by 3084

Abstract

An embedded piezoelectric transducer was developed for monitoring the corrosion process of reinforcement bars in concrete based on the piezoelectric impedance technique. The electrochemical method was employed to accelerate the corrosion process of the reinforcement bar with relative mass loss of 0.5–10%, and [...] Read more.

An embedded piezoelectric transducer was developed for monitoring the corrosion process of reinforcement bars in concrete based on the piezoelectric impedance technique. The electrochemical method was employed to accelerate the corrosion process of the reinforcement bar with relative mass loss of 0.5–10%, and the resistance spectra of the piezoelectric transducers were investigated to assess the corrosion process. The results show that the corrosion process of the reinforcement bar has significant influence on the resistance spectra of the piezoelectric transducers. Statistical parameters were used to intuitively evaluate the corrosion evolution based on variations of the resistance spectra. The corrosion process of reinforcement bar in concrete can be classified into three periods; that is, the initial period when the relative mass loss is less than 2%, the developing period at a relative mass loss of 2–4%, and the rapid corrosion period when the relative mass loss is higher than 4%. Full article

(This article belongs to the Special Issue Corrosion of Reinforcing Steel in Reinforced Concrete)

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