Continuous Fiber Reinforcement for Extrusion-Based 3D Concrete Printing

Fibre-reinforced concrete is a better option for reinforcement than conventional steel-reinforced concrete in many areas, such as tunnel construction, flooring, or bridge building in earthquake zones. This preference is due to the fact that steel, typically used in bars or mats, is associated with large crack widths and is vulnerable to corrosion. Therefore, this research focuses on the use of fibers made from corrosion-resistant materials like carbon. We present a continuous carbon fiber reinforcement, the individual filaments of which are bound together by a cement-based, mineral impregnation. This heat-resistant, high-performance impregnation remains flexible in its freshly impregnated state and offers a strong bond with concrete when hardened. This flexibility makes mineral-impregnated carbon fibers (MCF) particularly suitable for continuous reinforcement in concrete extrusion processes, especially in the context of 3D concrete printing (3DCP). MCF can be integrated into large concrete cross-sections deposited with a portal printer, as well as into finer concrete filaments deposited with an industrial robot arm, or in a stationary extruder where concrete is continuously molded horizontally into elements. The type and method of integration vary significantly depending on the respective extrusion process. This paper presents an overview of these methods, along with their respective advantages and disadvantages. Subsequently, the effects of the individual manufacturing processes on the mechanical performance of the composite and the crack development under tensile load are discussed. In combination with mineral-impregnated carbon fibers, these new manufacturing techniques offer enormous potential for specialised, individual elements.