3D printing as an automated manufacturing method for a carbon fiber-reinforced cementitious composite with outstanding flexural strength (105 N/mm2)

Abstract

As research interest in the additive manufacturing of cementitious materials for structural uses has been continuously increasing, the question of how to incorporate tensile reinforcement in an automated process has gained further importance. Our research describes a carbon fiber-reinforced cementitious composite produced by common extrusion techniques applied in 3D printing as a means to effectively control fiber alignment. Optimization of the mixture design and consistency allows for admixing up to 3 vol.-% chopped carbon fibers, leading to specimens that can reach a flexural strength exceeding 100 N/mm2 without the addition of further continuous reinforcement. Fiber integrity during the process was checked using optical microscopy. Analysis of the microstructure shows that approximately 70% of the fibers are aligned within ± 5° of a preferential direction. Micromechanical single-fiber push-out tests confirm an interfacial fracture toughness typical for strain-hardening systems. The first insights into a ‘lost formwork’ approach commonly employed in 3D printing show that the reinforcement remains effective even when combined with nonreinforced mortar.

Influence of Concrete Shrinkage on the Behavior of Carbon Short-Fiber-Reinforced Concrete (CSFRC) under Tension

“…Thus, for 1 vol% of carbon fibers in the cement paste aligned in the stress direction, there is a 5.6-foldincrease in the strength of flexural cement paste compared with plain cement paste, while for 3 vol% of carbon fibers aligned in the stress direction, the increase in flexural cement paste strength is around 14.40-fold. In contrast to the flexural strength, the compressive strength decreases around 1.17 times for 1 vol% of carbon fibers and 1.22 times for 3 vol% of carbon fibers [11,14]. For 1 vol% of randomly dispersed carbon fibers, there is around a 2.45-fold increase in strength for the flexural cement paste compared with the plain cement paste [11].…”

Sewing Concrete Device—Combining In-Line Rheology Control and Reinforcement System for 3D Concrete Printing

“…Different materials can be used to reinforce concrete, such as steel [ 23 ], polymers [ 32 ], basalt [ 33 , 34 ], glass [ 35 , 36 ], carbon [ 37 ], or even natural fibers [ 38 ], and they have already been tested, often with the same observation that they increase the strength and ductility of concrete structures. It is also well known that the bond strength between concrete and fibers is a key parameter in the reinforcement efficiency.…”