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16 pages, 4101 KiB

Open AccessArticle

Bridging the Gap: Assessing Material Performance of Laboratory Specimens and Concrete Structures

by Juan M. Lozano-Valcarcel, David Ov, Thomas Kränkel, Christoph Gehlen and Rolf Breitenbücher

Materials 2023, 16(12), 4306; https://doi.org/10.3390/ma16124306 - 10 Jun 2023

Viewed by 962

Abstract

Chloride ingress and carbonation pose a significant risk of steel rebar corrosion in concrete structures. Various models exist to simulate the initiation phase of rebar corrosion, addressing both carbonation and chloride ingress mechanisms separately. These models also consider the environmental loads and material [...] Read more.

Chloride ingress and carbonation pose a significant risk of steel rebar corrosion in concrete structures. Various models exist to simulate the initiation phase of rebar corrosion, addressing both carbonation and chloride ingress mechanisms separately. These models also consider the environmental loads and material resistances, typically determined through laboratory testing based on specific standards. However, recent findings show significant differences between material resistances obtained from standardized laboratory specimens and those extracted from real structures, with the latter exhibiting inferior performance on average. To address this issue, a comparative study was conducted between laboratory specimens and on-site test walls or slabs, all cast using the same concrete batch. This study encompassed five construction sites featuring different concrete compositions. While laboratory specimens adhered to European curing standards, the walls were subjected to formwork curing for a predetermined period (typically 7 days) to simulate practical conditions. In some instances, a portion of the test walls/slabs received only one day of surface curing to emulate inadequate curing conditions. Subsequent testing of compressive strength and resistance to chloride ingress revealed that field specimens exhibited lower material resistance compared to their laboratory counterparts. This trend was also observed in the modulus of elasticity and carbonation rate. Notably, shorter curing periods further compromised performance, particularly resistance to chloride ingress and carbonation. These findings highlight the importance of establishing acceptance criteria not only for concrete delivered to construction sites but also for ensuring the quality of the actual structure. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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17 pages, 2879 KiB

Open AccessArticle

On the Chloride Distribution in Concrete and Mortar Samples after an RCM Test

by Hannah Drenkard, Christian Fischer, Veit Sauer and Christoph Gehlen

Materials 2023, 16(8), 2952; https://doi.org/10.3390/ma16082952 - 7 Apr 2023

Cited by 2 | Viewed by 1410

Abstract

It is of essential need to face the challenges of CO₂ reduction in industrial cement and concrete production reliable test methods in order to evaluate the performance of concretes, especially with regard to the service life of our infrastructure. The rapid chloride [...] Read more.

It is of essential need to face the challenges of CO₂ reduction in industrial cement and concrete production reliable test methods in order to evaluate the performance of concretes, especially with regard to the service life of our infrastructure. The rapid chloride migration test (RCM test) is a standard method to assess the resistance against chloride ingress of concrete. However, during our study, certain critical questions arose with regard to the chloride distribution. The sharp chloride ingress front based on the model assumptions contradicted the shallow gradient of the experimental data. For this reason, investigations on chloride distribution in concrete and mortar samples after RCM tests were performed. The focus was on the factors influencing the extraction, e.g., time after RCM test and the location on sample. Furthermore, differences between concrete and mortar samples were investigated. The investigations showed that no sharp gradient on concrete samples was found due to the extremely uneven chloride front. In contrast, the theoretical profile shape was instead demonstrated on mortar specimens. The prerequisite for this result is that the drill powder must be taken directly after the completion of the RCM test from very uniform penetration areas. Thus, the model assumptions on the chloride distribution via the RCM test could be confirmed. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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25 pages, 4446 KiB

Open AccessArticle

Gum Arabic Nanoparticles as Green Corrosion Inhibitor for Reinforced Concrete Exposed to Carbon Dioxide Environment

by Mohammad Ali Asaad, Ghasan Fahim Huseien, Mohammad Hajmohammadian Baghban, Pandian Bothi Raja, Roman Fediuk, Iman Faridmehr and Fahed Alrshoudi

Materials 2021, 14(24), 7867; https://doi.org/10.3390/ma14247867 - 19 Dec 2021

Cited by 16 | Viewed by 3351

Abstract

The inhibiting effect of Gum Arabic-nanoparticles (GA-NPs) to control the corrosion of reinforced concrete that exposed to carbon dioxide environment for 180 days has been investigated. The steel reinforcement of concrete in presence and absence of GA-NPs were examined using various standard techniques. [...] Read more.

The inhibiting effect of Gum Arabic-nanoparticles (GA-NPs) to control the corrosion of reinforced concrete that exposed to carbon dioxide environment for 180 days has been investigated. The steel reinforcement of concrete in presence and absence of GA-NPs were examined using various standard techniques. The physical/surface changes of steel reinforcement was screened using weight loss measurement, electrochemical impedance spectroscopy (EIS), atomic force microscopy and scanning electron microscopy (SEM). In addition, the carbonation resistance of concrete as well screened using visual inspection (carbonation depth), concrete alkalinity (pH), thermogravimetric analysis (TGA), SEM, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The GA-NPs inhibitor size was also confirmed by transmission electron microscopy (TEM). The results obtained revealed that incorporation of 3% GA-NPs inhibitor into concrete inhibited the corrosion process via adsorption of inhibitor molecules over the steel reinforcement surface resulting of a protective layer formation. Thus, the inhibition efficiency was found to increase up-to 94.5% with decreasing corrosion rate up-to 0.57 × 10⁻³ mm/year. Besides, the results also make evident the presence of GA-NPs inhibitor, ascribed to the consumption of calcium hydroxide, and reduced the Ca/Si to 3.72% and 0.69% respectively. Hence, C-S-H gel was developed and pH was increased by 9.27% and 12.5, respectively. It can be concluded that green GA-NPs have significant corrosion inhibition potential and improve the carbonation resistance of the concrete matrix to acquire durable reinforced concrete structures. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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19 pages, 102049 KiB

Open AccessArticle

Analytical and Numerical Investigation of an Electrochemical Chloride Barrier for Reinforced Concrete Structures

by Carla Driessen-Ohlenforst and Michael Raupach

Materials 2021, 14(21), 6728; https://doi.org/10.3390/ma14216728 - 8 Nov 2021

Viewed by 1147

Abstract

During the development of a carbon-reinforced mortar interlayer for bridges, the idea of an electrochemical chloride barrier arose. An electrical field is generated between two carbon meshes, and the negatively charged chloride ions are held on the polarized upper carbon mesh to prevent [...] Read more.

During the development of a carbon-reinforced mortar interlayer for bridges, the idea of an electrochemical chloride barrier arose. An electrical field is generated between two carbon meshes, and the negatively charged chloride ions are held on the polarized upper carbon mesh to prevent chloride-induced corrosion in the reinforcement. Laboratory tests unexpectedly showed that higher voltages lead to an increase in chloride ions for certain depths of the reference probes. This paper discusses the implementation of analytical and numerical models that finally explain the effect only by the acting diffusion and migration with the help of a finite differences model and finite elements simulations. The effect of the local minimum is limited to positions above the depth of the first carbon layer of the test specimens. It is caused by the lines of the electrical field between the first and second carbon layer. According to the experimental and finite elements simulation results, higher voltages lead to lower chloride concentrations for all positions below the first carbon layer only after sufficient time duration. Therefore, the intended effect of an electrochemical chloride barrier can in general only be observed and confirmed after a certain time depending on position, conditions and parameters. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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28 pages, 5410 KiB

Open AccessEditor’s ChoiceArticle

Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures

by Pejman Azarsa, Rishi Gupta, Peiman Azarsa and Alireza Biparva

Materials 2021, 14(21), 6508; https://doi.org/10.3390/ma14216508 - 29 Oct 2021

Cited by 8 | Viewed by 2005

Abstract

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered [...] Read more.

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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18 pages, 6171 KiB

Open AccessArticle

Impact of Induction Furnace Steel Slag as Replacement for Fired Clay Brick Aggregate on Flexural and Durability Performances of RC Beams

by Md Jihad Miah, Md. Kawsar Ali, Ye Li, Adewumi John Babafemi and Suvash Chandra Paul

Materials 2021, 14(21), 6268; https://doi.org/10.3390/ma14216268 - 21 Oct 2021

Cited by 9 | Viewed by 2219

Abstract

This research investigates the flexural and durability performances of reinforced concrete (RC) beams made with induction furnace steel slag aggregate (IFSSA) as a replacement for fired clay brick aggregate (FCBA). To achieve this, 27 RC beams (length: 750 mm, width: 125 mm, height: [...] Read more.

This research investigates the flexural and durability performances of reinforced concrete (RC) beams made with induction furnace steel slag aggregate (IFSSA) as a replacement for fired clay brick aggregate (FCBA). To achieve this, 27 RC beams (length: 750 mm, width: 125 mm, height: 200 mm) were made with FCBA replaced by IFSSA at nine replacement levels of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 80%, and 100% (by volume). Flexural tests of RC beams were conducted by a four-point loading test, where the deflection behavior of the beams was monitored through three linear variable displacement transducers (LVDT). The compressive strength and durability properties (i.e., porosity, resistance to chloride ion penetration, and capillary water absorption) were assessed using the same batch of concrete mix used to cast RC beams. The experimental results have shown that the flexural load of RC beams made with IFSSA was significantly higher than the control beam (100% FCBA). The increment of the flexural load was proportional to the content of IFSSA, with an increase of 27% for the beam made with 80% IFSSA than the control beam. The compressive strength of concrete increased by 56% and 61% for the concrete made with 80% and 100% IFSSA, respectively, than the control concrete, which is in good agreement with the flexural load of RC beams. Furthermore, the porosity, resistance to chloride ion penetration, and capillary water absorption were inversely proportional to the increase in the content of IFSSA. For instance, porosity, chloride penetration, and water absorption decreased by 43%, 54%, and 68%, respectively, when IFSSA entirely replaced FCBA. This decreasing percentage of durability properties is in agreement with the flexural load of RC beams. A good linear relationship of porosity with chloride penetration resistance and capillary water absorption was observed. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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9 pages, 2098 KiB

Open AccessArticle

Evaluation of the Corrosion Behavior of Reinforced Concrete with an Inhibitor by Electrochemical Impedance Spectroscopy

by JangHyun Park and MyeongGyu Jung

Materials 2021, 14(19), 5508; https://doi.org/10.3390/ma14195508 - 23 Sep 2021

Cited by 12 | Viewed by 2310

Abstract

In this study, the effect of NaCl and LiNO₂ content on the deterioration of embedded rebars in concrete due to corrosion was examined by measuring the natural potential and impedance. Wet–dry cycles were performed to accelerate the corrosion of embedded rebars in [...] Read more.

In this study, the effect of NaCl and LiNO₂ content on the deterioration of embedded rebars in concrete due to corrosion was examined by measuring the natural potential and impedance. Wet–dry cycles were performed to accelerate the corrosion of embedded rebars in reinforced concrete, following which the potential and impedance corresponding to the cycles were measured. For the reinforced concrete containing only NaCl, the passive film of the embedded rebar surfaces deteriorated after two weeks of accelerated corrosion, and its polarization resistance decreased. When 0.6 M LiNO₂ per NaCl was added, the reinforced concrete deteriorated at the same rate as the normal embedded rebars, and the polarization resistance was higher than the initial values. When 1.2 M LiNO₂ per NaCl was added, the passive film of the embedded rebars remained intact even after 10 weeks of accelerated corrosion, protecting the rebars from deterioration. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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Review

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32 pages, 3984 KiB

Open AccessReview

A Critical Review of Existing Test-Methods for External Sulfate Attack

by Mike Jabbour, Othman Omikrine Metalssi, Marc Quiertant and Véronique Baroghel-Bouny

Materials 2022, 15(21), 7554; https://doi.org/10.3390/ma15217554 - 27 Oct 2022

Cited by 9 | Viewed by 1954

Abstract

External sulfate attack (ESA) of cementitious materials has been studied worldwide for a very long time. This physical/chemical interaction between sulfate ions and the cement hardened elements affects the long-term durability of concrete structures: cracking, spalling or strength loss of concrete structures. To [...] Read more.

External sulfate attack (ESA) of cementitious materials has been studied worldwide for a very long time. This physical/chemical interaction between sulfate ions and the cement hardened elements affects the long-term durability of concrete structures: cracking, spalling or strength loss of concrete structures. To study these damaging phenomena, some standardized and non-standardized accelerated aging tests are used to evaluate the performance of cements in sulfate-rich environments. However, these existing methods do not adequately predict field performance and some shortcomings or deficiencies still exist: change of degradation mechanisms when using high concentrations of sulfate, variable boundary conditions and small specimens compared to the real concrete structures. In this work, a critical review of some existing test methods and foreign national standard methods for ESA are presented, analyzed, and discussed. This results in some proposed recommendations for improving these methods to meet the needs of structure managers. Full article

(This article belongs to the Special Issue Reinforced Concrete Structures for Durability and Corrosion Resistance)

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