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Boubitsas D.,CBI Swedish Cement and Concrete Research Institute | Boubitsas D.,Lund University | Tang L.,CBI Swedish Cement and Concrete Research Institute | Tang L.,Chalmers University of Technology
Materials and Structures/Materiaux et Constructions | Year: 2015

This paper describes a part of the work in the development of a “standard” test method for determining chloride threshold values required to initiate corrosion on reinforcement in concrete. The prerequisites of the test set-up are that the test conditions should be reasonably comparable to those in service and the test method should be fairly reproducible and as rapid as possible concerning the slow diffusion nature of the investigated phenomenon. This paper presents the results from a study on the influence of steel bar surface condition on chloride induced corrosion. Various electrochemical techniques were employed in the study to monitor the corrosion behaviour of the embedded bars with three different surface conditions. It is shown that the steel surface condition has a strong effect on the corrosion initiation of reinforcement in concrete, and can likely be the most decisive parameter attributing to the variability in the reported chloride threshold values. © 2014, RILEM. Source

Zandi K.,Chalmers University of Technology | Zandi K.,CBI Swedish Cement and Concrete Research Institute
Structure and Infrastructure Engineering | Year: 2015

The aim of this study is to enhance our understanding of anchorage capacity in reinforced concrete structures with corrosion-induced cover spalling. Our objectives were to study the influence of corrosion-induced cover spalling on bond strength, and to validate an existing one-dimensional (1D) analysis for anchorage capacity in such cases. Thus, earlier developed bond and corrosion models suited for detailed three-dimensional (3D) finite element (FE) analysis were first combined with a new computation scheme to simulate corrosion-induced cover spalling. The 1D and 3D FE analyses were validated through two types of experiments, i.e. eccentric pull-out tests and beam tests, as well as a comparison with an existing empirical model. The application of 3D FE analysis showed that the corrosion of stirrups advances the emergence of cracking and spalling, while bond strength is only slightly influenced by the corrosion of stirrups after cover spalling if yielding of stirrups has not taken place. Moreover, it was shown that stresses in the stirrups due to corrosion in adjacent bars rapidly diminished within a short distance from the main bar, and that the corrosion of stirrups influenced the shear capacity more prominently than the induced stresses in stirrups due to the corrosion of main bars. © 2015 Taylor & Francis. Source

Tang L.,Chalmers University of Technology | Tang L.,CBI Swedish Cement and Concrete Research Institute | Lindvall A.,Thomas Concrete Group AB
International Journal of Structural Engineering | Year: 2013

This paper presents the results from validation of models for prediction of chloride ingress in concrete exposed in de-icing salt road environment. Three models including the simple error-function complement (ERFC) model, the DuraCrete model and the ClinConc model, were evaluated using the measurement data collected from both the field exposure site after over ten years exposure and the real road bridges after 25-30 years in service. The sensitivity of input parameters in each model is analysed. The results show that, among different input parameters, the age factor is the most sensitive one. The simple ERFC model significantly overestimates chloride ingress. The DuraCrete model, if the input parameters are properly selected, may give a reasonably good prediction, otherwise often underestimates chloride ingress. The ClinConc model in general gives fairly good predictions for chloride ingress in de-icing salt road environment with heavy traffic at high speed. Copyright © 2013 Inderscience Enterprises Ltd. Source

Lundgren K.,Chalmers University of Technology | Tahershamsi M.,Chalmers University of Technology | Zandi K.,CBI Swedish Cement and Concrete Research Institute | Plos M.,Chalmers University of Technology
Materials and Structures/Materiaux et Constructions | Year: 2015

Many studies on the structural effects of corrosion in reinforcement have been conducted. However, most of them are based on artificially corroded test specimens. Thus, the knowledge available entails one major uncertainty, i.e. whether the results are reliable enough to be used for naturally corroded structures. The purpose of this study was to develop a test method and carry out experiments on naturally corroded specimens taken from an existing structure to investigate the anchorage capacity. Beam specimens were taken from the edge beams of a bridge at repair. The specimens showed corrosion-induced damage to a varying extent from no sign of corrosion to extensive cracking and spalling of the concrete cover. A four-point bending test indirectly supported by suspension hangers was chosen. The beams were strengthened with transverse reinforcement around the suspension hangers to avoid premature failure. Eight successful tests were carried out; in all these tests, diagonal shear cracks preceded a splitting induced pull-out failure; i.e. anchorage failure was achieved as intended. The results showed around 10 % lower capacity for the corroded specimens than for the reference ones. The average bond stress in the anchorage zone was estimated based on the applied load and available anchorage length. The stress was about 16 % lower in the beams with corrosion cracks, and 9 % lower in the beams with cover spalling compared to the reference specimens; there was also a larger variation among the damaged specimens than for the reference specimens. The results extend our knowledge concerning the structural behaviour of corroded reinforced concrete structures during field conditions. © 2014, RILEM. Source

Portal N.W.,Chalmers University of Technology | Lundgren K.,Chalmers University of Technology | Wallbaum H.,Chalmers University of Technology | Malaga K.,CBI Swedish Cement and Concrete Research Institute
Journal of Materials in Civil Engineering | Year: 2015

The building construction industry is in need of sustainable materials and solutions. A novel building material, such as textilereinforced concrete (TRC), could be used to meet this demand. Textile-reinforced concrete is a combination of fine-grained concrete and multiaxial textile fabrics that has been fundamentally researched over the past decade. TRC-based research has explored various facets of this composite material, such as its structural functionality, production, applicability, and design. One key aspect that is still missing, however, is a comprehensive review of the sustainable potential of this material in terms of its input-output and durability that suitably answers to requirement No. 7 of EU's Construction Products Regulation. This article provides qualitative and quantitative evaluation of the sustainable potential and prospective development of TRC particularly reinforced by alkali-resistant (AR) glass, carbon, or basalt fibers. Based on the outcome of this evaluation, carbon textile fibers were observed to hold the optimal potential mechanical behavior; additionally, it was revealed through the conducted life-cycle assessment (LCA) that basalt had the least cumulative energy demand, whereas carbon had the least environmental impact. © 2014 American Society of Civil Engineers. Source

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