Multiple cracking of carbon-reinforced concrete
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Project data
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Short description
Joints are integral components in planar structural elements made of concrete, e.g., industrial surfaces, parking and traffic areas, retaining walls, etc., in order to avoid unwanted forced cracking. Thermal and hygric-induced inherent deformations are concentrated in movement and dummy joints, into which liquid media including contained pollutants (chlorides, sulfates, alkalis, hydrocarbons, etc.) can penetrate. This impairs the durability of the components and possibly leads to contamination of the underlying soil layers or even washout. To prevent the above-mentioned damage, joint sealants are used that have a durability limited to a few years.
The collaborative project of Ruhr-University Bochum and TU Dresden deals with an alternative solution concept for joint covering. With the aid of thin, textile-reinforced concrete layers, joints in unreinforced or only weakly reinforced concrete components are covered. Carbon-fiber reinforcement, which is characterized by high corrosion resistance and comparatively high tensile strength, is preferred as reinforcement. Due to the large singular joint movements in the base member, a wide single crack would occur in conventional concrete cover layers. The aim is for the fine, high-strength carbon reinforcement to distribute the singular crack pattern to plural, much smaller cracks.
The joint covering made of carbon-reinforced concrete is subject to special stresses in the above-mentioned applications of two-dimensional components. These include tensile stresses that build up in the concrete surface layer during cold seasons as the joints open. Conversely, compressive stresses occur in warm seasons when the joints close. In large concrete surfaces, these stress states occur at joint intersections in two directions. In Dresden, the load-bearing and deformation behavior under uniaxial and biaxial tensile loading is being investigated. Different material combinations are tested. Crack development under tension and transverse tension, the bond behavior of carbon mesh and concrete, and the influence of transverse tension on the course of the bond stress-slip relationship are being investigated. Based on this, we want to develop a model to describe the bond between carbon mesh and concrete under biaxial loading. The collected findings are incorporated into practical regulations so that joint covering can be widely applied in this construction method.