Statistical relationship between mix properties and the interfacial transition zone around embedded rebar |
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| Affiliation: | 1. Technische Universität Braunschweig, Institute of Applied Mechanics, Pockelsstraße 3, 38106, Braunschweig, Germany;2. National Institute of Standards and Technology, Engineering Laboratory, Materials and Structural Systems Division, Stop 8615, 100 Bureau Drive, Gaithersburg, MD, 20899-8615, USA;3. Technische Universität Braunschweig, Institute of Building Materials, Concrete Construction and Fire Safety, Department of Building Materials, Beethovenstr. 52, 38106, Braunschweig, Germany;1. Federal Institute of Education, Science and Technology of Paraíba, R. Dep. Balduíno M. de Carvalho, 155/1104, 58.036-860 João Pessoa, Brazil;2. Civil and Environmental Engineering Postgraduate Programme, Federal University of Paraíba, 58051-900 João Pessoa, Brazil;3. Research Centre in Safety and Durability of Structures and Materials (CISDEM, UPM–CSIC), Madrid, Spain;4. Federal University of Campina Grande, Campina Grande, Brazil |
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| 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/m3 to 564 kg/m3. 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. |
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| Keywords: | Image analysis ITZ Steel Reinforcement Concrete composition Statistical method |
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