Schutz und Instandsetzung von Betonbauteilen mit genormten Produkten nach EN 1504

Repair and protection of concrete structures using products according to the standard EN 1504 The European series of standards EN 1504 for protection and repair of concrete structures is actually more or less finished. It consists of 10 main standards and 62 European test standards. The main standards EN 1504‐2 to 7 refer to the product classes surface protection systems, mortars, adhesives for strengthening, materials for filling of cracks and voids, anchoring products as well as protection materials for the steel surface. The principles for the use of the products and systems as well as the application of the products on site including quality assurance are regulated in parts 9 and 10. Furthermore the quality assurance for the products is described in part 8. In this way within the next months an extensive set of standards for protection and repair of concrete structures is available. Actually it is discussed, how this set of standards will be introduced in Germany. Due to different reasons it has been decided, that the parts for design and application will not be introduced in Germany, because the existing standards of the DAfStb “Protection and repair of concrete structures” as well as the ZTV‐ING have been used successfully for several years. To be able to use the European CE‐marked products for protection and repair of concrete structures in future in Germany, for surface protection, mortars, materials for filling of cracks and voids as well as steel coatings in the meantime additional standards (DIN V 18026 to 18028) have been worked out, while the adhesives and anchoring products will be handled via approvals as before. This paper describes, how protection and repair of concrete structures will be carried out in Germany with CE‐marked products according to EN 1504.     

Technische Textilien zur Bewehrung von Betonbauteilen

Textile Reinforcement for Concrete For the best transmission of tensile and bending forces in the composite material, the textile reinforcement material has to be inserted as long fibres laid in straight orientation and depending on the load. Through the development of textile manufacturing technologies filament yarns can be manufactured into open grid structures which increase the potential of alternative reinforcements. It is currently possible to manufacture load‐adapted textile structures. It is essential that the high‐performance mechanical properties of the alkali‐resistant glass fibres or carbon fibres used are maintained throughout the manufacturing process until the finished component is complete. Therefore the quality of the yarn orientation and the yarn distribution has to be obtained secured throughout the manufacturing process until the finished textile fabric is complete.     

Verformungsvorhersage von vorgespannten und nicht vorgespannten Betonbauteilen

Deformation Forecast of Prestressed and Non‐Prestressed Concrete Members Comparative investigations have shown that the limitation of deformation, based on a permitted slenderness ratio as possible according to DIN 1045‐1 for reinforced concrete elements, do not always achieve the desired success. An exact calculation of the structure deformation is absolutely necessary for prestressed components and in the case of a non‐accomplished slenderness proof for reinforced concrete members. In this paper significant material influences of the deformation forecast will be discussed, proceeding from universal views of the component deformation proof. It will be clear, that an exact deformation calculation is only restricted possible. An approximation procedure for practical use to the forecast of deformations of reinforced and prestressed concrete structures will be formulated, afterwards. The accuracy of this developed approximation procedure will be estimated with the aid of comparative studies. At this, the results of the simplified formulation correlate well with the values of complex, numeric investigations in a range of practical use.     

Transport von drückendem Wasser in Betonbauteilen

Effect of Water Pressure on Moisture Transport in Concrete Structural Components The effect of water pressure on moisture transport in concrete has been investigated. The uptake of water under pressure at an end surface of concrete cylinders and the release of moisture at the opposite dry surface were measured over a period of 500 days. In addition, ¹H NMR was used to observe directly the penetration of water into mortar prisms. The results show that penetration depth and amount of absorbed water are both limited by the self‐sealing effect in concrete. It is concluded that moisture transport through water‐tight concrete thicker than 200 mm is negligible for water pressures up to 5 bar. Self‐sealing also reduces liquid penetration when concrete is exposed to NaCl solutions under pressure. The penetration of salt solutions is slower than water, less liquid being taken up.     

Effizienzsteigerung von Textilbeton durch Einsatz textiler Bewehrungen nach dem erweiterten Nähwirkverfahren

Textilbeton ist ein neuer, effektiver und sehr innovativer Baustoff zur Verstärkung von Tragwerken. Im Rahmen der laufenden Forschung stehen die weitere Verbesserung des Verstärkungsverfahrens und die stetige Weiterentwicklung der Faser‐Matrix Kombination im Mittelpunkt der Untersuchungen. Aufgrund der hohen Garnzugfestigkeiten sind bei Verwendung textiler Bewehrungen aus Carbon sehr effektive Verstärkungen herstellbar. Bei ungünstiger Konfiguration der textilen Bewehrungen können jedoch verbund‐ und festigkeitsschädigende Rissbildungen innerhalb zugbeanspruchter Textilbetonbauteile auftreten. Diese Rissbildungseffekte werden in Abhängigkeit von der Belastung maßgeblich durch die wirkenden Verbundkräfte und die verarbeitungsbedingte Garnwelligkeit beeinflusst. Dabei ist die Gefahr eines Verbundversagens durch Delamination besonders in den Bereichen der Lasteinleitung in die textile Bewehrung, wie z. B. Endverankerungen und Übergreifungsstößen, kritisch. Dies führt zu einer Reduzierung der nutzbaren Zugtragfähigkeit der textilen Bewehrung im Gesamtbauteil. Um die Effizienz der textilen Bewehrung zu erhöhen, wurde daher ein verbessertes Textilherstellungsverfahren auf Basis der Nähwirktechnik entwickelt. Dadurch wird die ungünstig wirkende Garnwelligkeit deutlich reduziert. Der vorliegende Aufsatz beschreibt vergleichende Untersuchungen der Verbund‐ und Festigkeitseigenschaften zugbeanspruchter Textilbetonbauteile. Die Ergebnisse zeigen, dass mit der Entwicklung des erweiterten Nähwirkprozesses ein maßgeblicher Schritt im Hinblick auf eine weitere Verbesserung der Eigenschaften des Textilbetons erreicht werden konnte. Efficiency Increase of Textile Reinforced Concrete by Use of Textile Reinforcements from the Extended Warp Knitting Process The composite material textile reinforced concrete (TRC) is a new, effective and very innovative method for the strengthening of load bearing structures. Apart from further improvements to the strengthening methods, a continual further development of the fibre‐matrix combination is at the centre of ongoing research. Due to the high tensile strengths of textile reinforcements made of carbon, it enables very effective strengthening of concrete constructions. However, if the textile fabrics are unfavourably configured, bond and strength damaging crack formations within TRC members can occur. Depending on the load, these crack formation effects are substantially influenced by the bond and the size of yarn undulation, which depends on the processing of the fabric. The danger of bond failure by delamination, which particularly occurs in areas of concentrated load introduction into the textile reinforcement, such as final anchorages and overlaps, is especially critical. It results in a reduction of the usable tensile load bearing capacity in the entire member. For this reason, an improved textile manufacturing method based on warp knitting technology was developed. By means of this method, yarn undulation can be reduced considerably. The article on hand describes comparative examinations of the bond and strength properties of tensile loaded TRC elements. The results show that the development of the extended warp knitting process was a substantial step toward a further improvement of the properties of TRC.