New thermoplastic carbon fiber reinforced polymer rebars and stirrups

• Published in: Structural concrete : journal of the FIB 2022-04, Vol.23 (2), p.923-938
• Main Authors: Apitz, Andreas, Schmitz, Jonas, Hückler, Alex, Schlaich, Mike
• Format: Article
• Language: English
• Subjects: carbon; Carbon fiber reinforced concretes; Carbon fiber reinforced plastics; carbon fiber reinforced polymer; Carbon fiber reinforcement; CFRP; Engraving; Fiber reinforced polymers; Prestressing; Rebar; rebars; Recyclability; Reinforced cements; reinforcement; Stirrups; Tensile tests; thermoplastic
• ISSN: 1464-4177; 1751-7648
• DOI: 10.1002/suco.202100434

Attributed to its extraordinary strength and durability, the future of reinforcing and prestressing material in reinforced cement concrete (RCC) structures most likely belongs to carbon fiber reinforced polymer (CFRP). However, CFRPs are rarely employed in real structures till now, since the technology to manufacture CFRP rebars and stirrups is still evolving. This is especially applicable for manufacturing of rebars with surface profiles (ribs) and bent sections for stirrups. Unlike thermoset polymers, thermoplastic polymers are highly viscous prior to curing and can be melted and cured again. This creates possibilities for the production technology as well as recyclability. In this paper, new thermoplastic CFRP rebars and stirrups are introduced, which are manufactured in a novel way. The rips are engraved directly after pultrusion and the stirrups are thermoformed out of a straight and already profiled bar. A holistic approach is applied, which enables to evaluate the mechanical overall performance and to compare it with existing products in a reasonable way. This requires the introduction of new parameters, for example the fiber utilization rate. The novel CFRP reinforcement is investigated through tensile tests on bars and stirrups as well as bond tests. The bond performance is quite similar to existing products. Especially while considering how efficient the fibers are utilized in the CFRP bar, the tensile performance and the quality of the stirrups is excellent.