C³ - Carbon Concrete Composite
Structures made of carbon concrete are optimally designed and constructed when the carbon reinforcement is prestressed. The success story of the prestressed concrete began with the advent of high-tensile prestressing steel, which made it possible to introduce permanently high prestressing forces into the concrete. The transition from the prestressing steel to the even firmer, lighter and corrosion-resistant carbon is an almost natural development of this powerful construction material. By prestressing Carbon reinforcement slimmer cross-sections that are durable and robust can be achieved. Prestressed carbon concrete is to be researched in two subprojects (Part A: Bridge Systems for road traffic, Part B: Shell Structures).
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- Dr.-Ing. Alex Hückler
- Dipl.-Ing. Andreas Apitz
- Dipl.-Ing. Juan Pablo Osman Letelier
- Sherif Mohareb, M.Sc.
The development of a bridge system with spans of 35 to 45 m without a center support made of prestressed carbon concrete without joints and bearings - is the goal of the subproject A. It includes the design of prefabricated construction elements, the use of high-strength concrete as well as tendons and reinforcement made of carbon. The bridge system should be used for overpasses over up to three-lane motorways. Since the end of the nineties there has been a progressive shift in this market segment away from the prestressed concrete and towards the composite prefabricated construction method. Through the efficient use of carbon, prestressed concrete can catch up again here. In the project, a high-quality design is developed and critical points such as the bending behaviour (ductility), the introduction of the clamping force as well as the carbon tendon are investigated experimentally. At the end of the project, a ready-to-use precast girder with real dimensions will be produced as a demonstrator, where manufacturability is evaluated and long-term measurements are carried out. The subproject provides the basics for the implementation of a pilot project. In addition to the development of the bridge system, the project also focuses on the further development of prestressing technology in carbon concrete. Compact, reusable anchoring systems will be developed. Due to the compactness of the anchoring elements, the application field of prestressed carbon concrete can be extended to the classical building construction area, thereby revealing the potential and the versatility of the new construction material.
The development of shell structures of prestressed carbon concrete is the main object of subproject B. The shell structures can be planar and uniaxial or biaxial curved. The shell thickness of reinforced concrete structures is decisively determined by the corrosion protection, which is not needed in the case of the use of carbon reinforcement. Due to the additional prestressing of the flat net reinforcement made of carbon, very lightweight structures with high stiffness are possible. Such shell constructions are particularly material-efficient (more economical use of reinforcement, less concrete) and can be used, among others, in container constructions for aggressive media due to their tightness and corrosion resistance. Economical manufacturing processes are made possible by adaptive and segmented formwork constructions. The potential of the prestressing of carbon net reinforcement for thin shell elements is evaluated exemplary on folded structures and curved concrete shells. For this purpose, the basic elements rod (1D), plate (2D) and curved shell (3D) are experimentally investigated and tested. In a next step, demonstrators of commercially usable products in building and industrial construction (PI plates and trapezoidal folded plates) will be developed. The project ends with a demonstrator for a shell container, where the long-term behaviour is investigated.
- Apitz, A.: Suitability of CFRPs for Prestressing of Concrete Bridges. In IABSE - Young Engineers Colloquium 2017, 20–21.