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Amnon Katz - One of the best experts on this subject based on the ideXlab platform.
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steel concrete interface influence on chloride threshold for corrosion empirical reinforcement to theory
Construction and Building Materials, 2020Co-Authors: Amit Kenny, Amnon KatzAbstract:Abstract Reinforcement corrosion is a common cause for reinforced concrete structure deterioration. One of the main causes for reinforcement corrosion is chloride ingress to the concrete. Published work hint at a relationship between susceptibility to chloride induced corrosion and the interface between the concrete and the Rebar, known as the steel–concrete interface (SCI). This paper presents an investigation of the relationship between the chloride threshold for chloride-induced corrosion and the properties of the SCI around Embedded Rebar. The relationship was investigated using 16 different concrete mixes. SCI properties were extracted using automated image analysis. The chloride threshold was found to decrease with the distance between the Rebar surface and the concrete solids. In the case of horizontal Rebar, the chloride threshold decreased with SCI thickness as well. These results agree with the theory of concentration polarization in localized corrosion and may explain the variety of chloride threshold values reported in the literature.
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statistical relationship between mix properties and the interfacial transition zone around Embedded Rebar
Cement & Concrete Composites, 2015Co-Authors: Amit Kenny, Amnon KatzAbstract:Abstract The relationship between concrete mix properties and the properties of the interfacial transition zone (ITZ) formed around Embedded Rebar was investigated. Multiple samples of various mix compositions and bar orientations were prepared so as to represent common concrete technology. Water-to-cement ratios varied from 0.40 to 0.65 and powder (cement + limestone filler) contents ranged from 362 kg/m 3 to 564 kg/m 3 . Over 1300 BSE images of the steel–concrete interface were taken and analyzed automatically. Statistical methods were used to identify correlations between ITZ properties and mix composition or fresh mix properties. A single large void was identified beneath all horizontal bars regardless of concrete composition. The ITZ around vertical bars was more uniform and extended around the entire Rebar. No clear relationship was found between ITZ thickness and mix composition or fresh mix properties for either vertical or horizontal bar orientations. The degree of ITZ variability beneath horizontal bars clearly depends, however, on the bleeding properties of the mix. The distance from steel surface to the closest concrete solid, which influences the chemistry over the surface of the steel, is affected by precipitation of hydration products in horizontal bars, but not by mix composition.
Amit Kenny - One of the best experts on this subject based on the ideXlab platform.
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steel concrete interface influence on chloride threshold for corrosion empirical reinforcement to theory
Construction and Building Materials, 2020Co-Authors: Amit Kenny, Amnon KatzAbstract:Abstract Reinforcement corrosion is a common cause for reinforced concrete structure deterioration. One of the main causes for reinforcement corrosion is chloride ingress to the concrete. Published work hint at a relationship between susceptibility to chloride induced corrosion and the interface between the concrete and the Rebar, known as the steel–concrete interface (SCI). This paper presents an investigation of the relationship between the chloride threshold for chloride-induced corrosion and the properties of the SCI around Embedded Rebar. The relationship was investigated using 16 different concrete mixes. SCI properties were extracted using automated image analysis. The chloride threshold was found to decrease with the distance between the Rebar surface and the concrete solids. In the case of horizontal Rebar, the chloride threshold decreased with SCI thickness as well. These results agree with the theory of concentration polarization in localized corrosion and may explain the variety of chloride threshold values reported in the literature.
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statistical relationship between mix properties and the interfacial transition zone around Embedded Rebar
Cement & Concrete Composites, 2015Co-Authors: Amit Kenny, Amnon KatzAbstract:Abstract The relationship between concrete mix properties and the properties of the interfacial transition zone (ITZ) formed around Embedded Rebar was investigated. Multiple samples of various mix compositions and bar orientations were prepared so as to represent common concrete technology. Water-to-cement ratios varied from 0.40 to 0.65 and powder (cement + limestone filler) contents ranged from 362 kg/m 3 to 564 kg/m 3 . Over 1300 BSE images of the steel–concrete interface were taken and analyzed automatically. Statistical methods were used to identify correlations between ITZ properties and mix composition or fresh mix properties. A single large void was identified beneath all horizontal bars regardless of concrete composition. The ITZ around vertical bars was more uniform and extended around the entire Rebar. No clear relationship was found between ITZ thickness and mix composition or fresh mix properties for either vertical or horizontal bar orientations. The degree of ITZ variability beneath horizontal bars clearly depends, however, on the bleeding properties of the mix. The distance from steel surface to the closest concrete solid, which influences the chemistry over the surface of the steel, is affected by precipitation of hydration products in horizontal bars, but not by mix composition.
Jay Sanjayan - One of the best experts on this subject based on the ideXlab platform.
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chloride ingress and steel corrosion in geopolymer concrete based on long term tests
Materials & Design, 2017Co-Authors: Chandani Tennakoon, Ahmad Shayan, Jay SanjayanAbstract:Abstract Alkali activated binders (geopolymer) is an emerging technology to produce concrete without the use of any Ordinary Portland Cement (OPC) by alkali activation of alumino-silicate source materials such as fly ash and/or slag. Limited knowledge on durability issues like corrosion behaviour of reinforced geopolymer concrete impedes the usage of this technology in structural applications. This study explored the chloride permeability and initiation of chloride induced corrosion of geopolymer concrete in accelerated chloride environment using longer test period. Corrosion initiation was also monitored in Embedded Rebar in 2% chloride contaminated concrete. Corrosion state of the Rebar was monitored using non-destructive test method using Cu/CuSO4 reference electrode. The results showed that the apparent chloride diffusion coefficient of blended fly ash and slag geopolymer concrete is lower than that of OPC concrete. The diffusion coefficient also decreased with the increase of slag content in the binder. Blended fly ash and slag geopolymer concrete also exhibited higher aging factor than OPC concrete indicating improved resistance to chloride ingress with time. The study also showed that the Embedded Rebar in fly ash and slag based geopolymer concrete has higher protection against corrosion than a Rebar in OPC concrete even when the concrete is contaminated with significant levels of chloride.
Gurminder Minhas - One of the best experts on this subject based on the ideXlab platform.
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moisture transport and steel Rebar corrosion in repair composites incorporating nano fibrillated cellulose nfc
Construction and Building Materials, 2021Co-Authors: Obinna Onuaguluchi, Nemkumar Banthia, Keith Gourlay, Gurminder MinhasAbstract:Abstract Repair of deteriorating concrete infrastructure remains a major challenge. The concern is that current repair materials are not able to prevent premature failure after a repair has been performed. Thus, an engineered repair mortar that can enhance the durability of repaired composites by mitigating moisture transport and its debilitating influence on deterioration mechanisms such as steel Rebar corrosion would be highly coveted. In this study, the influence of reinforcing a repair mortar with 0.1% by volume of Nano-Fibrillated Cellulose (NFC) on the capillary water transport in monolithic and composite specimens was investigated. Micro Computed Tomography (CT) imaging was also utilized in evaluating the microstructure of sorptivity test specimens. Thereafter, the influence of repair mortars on the corrosion behavior of deformed steel Rebar was investigated via natural and accelerated tests. In these tests, concrete substrates had an Embedded Rebar in it, and repair mortars were applied on the top creating a composite specimen with a repair interface. Some of the parameters measured were surface resistivity, half-cell potential, overlay delamination time, residual Rebar pullout load and Rebar corrosion degree. Sorptivity tests indicated that the NFC is indeed capable of refining the pore structure through internal curing and thus reducing the capillary uptake of water. Moreover, the tendency of the NFC to entrap micro voids, especially near the repair interface, thereby indirectly reducing moisture transport and saturation of composite specimens was confirmed by CT imaging. Natural and accelerated corrosion test results demonstrated that NFC addition inhibited Rebar corrosion as indicated by reduced Rebar corrosion degree and delayed delamination of the repair overlay. The NFC also provided superior surface resistivity and a higher Rebar pullout load capacity after corrosion.
Claudia P Ostertag - One of the best experts on this subject based on the ideXlab platform.
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acidification at Rebar concrete interface induced by accelerated corrosion test in aggressive chloride environment
Cement & Concrete Composites, 2020Co-Authors: Claudia P OstertagAbstract:Abstract The Rebar-concrete interface plays a critical role in initiating corrosion of steel reinforcing bars Embedded in concrete. The intimate physical contact between a steel Rebar and the Ca(OH)2-rich interfacial transition zone of concrete provides physical protection and buffering action against corrosion. However, the mechanism of the buffering action is not well understood and a systematic study has not yet been conducted. This paper investigates acidification at the Rebar-concrete interface, buffering capabilities of concrete made with 100% Portland cement and with 50% fly ash or ground-granulated slag as cement replacement, and corrosion behavior of the Embedded Rebar. It was found that a simple technique with filter paper wrapped around the steel Rebar under a high impressed anodic current and a severe chloride environment allowed for interface solution to be accumulated, squeezed out, and collected for analysis. The solutions had pH values less than 2, thus proving acidification at the interface during the accelerated corrosion test. With a high content of Ca(OH)2 in the matrix, the concrete with 100% cement as binder was shown to have a higher buffering capacity as compared to the matrix with 50% fly ash or slag as cement replacement. This acidification phenomenon promoted steel dissolution and subsequent corrosion activity, although the presence of cracks in the concrete cover could also play a dominant role in controlling the subsequent corrosion rates. Acidification was also shown to occur under natural corrosion of lower corrosion activity.