JEC COMPOSITES MAGAZINE - Issue #44 - October 2008 - Special Asia - 34

FEATURE “Reinforcement” fibre reinforcement materials are predominantly used for nonstructural applications, while carbon fibre materials are the preferred option for reinforcement of primary structures. g…/… Textile-reinforced concrete with high-performance carbon fibre grids strengthening layer. TRC strengthening is then accomplished by applying alternate layers of fine-grained concrete and textile reinforcement to existing RC members. Application to lightweight concrete structures Reinforcement with carbon fibre textile products has been used in hundreds of projects worldwide over the past few years. Some of them would certainly not have been possible without textile reinforcement. The typical dimensions of textile reinforcement and resulting TRCs are one order of magnitude smaller than that of RC, providing totally new opportunities for the construction industry. Suitable production methods include laminating, casting, spraying, spinning and injection moulding, while possible applications may be used in a host of structures from facade panels to lost formwork and pedestrian bridges. To demonstrate the stage of development of TRC applications, a small footbridge for pedestrians and cyclists was constructed for a local horticultural show in Oschatz, Germany. The Döllnitz Creek Bridge is a single-span girder using a segmental construction method with internal unbonded pre-stressing. The span of the superstructure is approximately 8.60 m and the width between handrails is 2.50 m. The pre-cast members were assembled in a concrete plant. By optimizing the arrangement of the textile reinforcement to the flow of forces and using highstrength textile reinforcement, the amount of reinforcement can be considerably reduced and cost-effective structures are possible. The Döllnitz Creek Bridge weighs only a quarter of what a traditional RC bridge would have weighed. New construction elements can be easily produced. TRC façade elements are already in service and standing the test of time, while a second bridge with a span of more than 16 m has been coping well with the daily flow of traffic in Kempten, Germany, since the summer of 2007. Due to the open grid structure, the textile reinforcement grid has a mechanical interlock in the concrete matrix. This results in excellent anchorage behaviour. The carbon fibre itself does not require substantial concrete cover due to its resistance to corrosion and alkalis, acids or chemicals in general. The surface design of the strengthening layer can vary within a wide range. A wide range of design options are available today for plasters that can also be utilized in TRC-applications, provided that suitable mixtures for matrices are used and the final layer is appropriately treated. These opportunities extend textilereinforced concrete applications into completely new fields. Besides slender new concrete elements, strengthening of existing concrete structures by thin textile-reinforced concrete layers is already possible. In the near future, it is very plausible that we will find TRCs in concrete applications like roofs and balconies, noise barriers, precast elements and lost formwork for slabs, beams and columns, sandwich elements, tanks and lines. Glass SGL carbon grid SGL Group has developed a textile reinforcing grid for TRC using the SIGRAFIL® C PAN-based 50k carbon fibre (Figures 4 & 5). Used as continuous tow, SIGRAFIL® C is ideal for weaving, prepregging, filament winding, carbon fibre-reinforced plastic (CFRP) components, advanced composites, multi-axial production, unidirectional tapes, extrusion, pultrusion and other conversion processes. Fig. 4: SIGRAFIL® C 50k carbon fibre. Fig. 5: Carbon grid embedded in concrete for testing. For applications in textile-reinforced concrete, heavy tow carbon fibre improves cost efficiency in several ways. SIGRAFIL® C offers an excellent price-to-performance ratio by using a less expensive carbon fibre with high tensile strength and high JEC Composites Magazine / No44 October 2008

JEC COMPOSITES MAGAZINE - Issue #44 - October 2008 - Special Asia

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