Investigation of helix-pultruded CFRP rebar geometry variants for carbon-reinforced concrete structures

Research output: Contribution to journalResearch articleContributedpeer-review


Carbon concrete is a new, promising class of materials in the construction industry. This corrosion-resistant reinforcement material leads to a reduction in the concrete cover required for medial shielding. This enables lean construction and the conservation of concrete and energy-intensive cement manufacturing. Bar-type reinforcement is essential for heavily loaded structures. The newly developed helix pultrusion is the first process capable of producing carbon fiber-reinforced polymer (CFRP) reinforcement bars with a topological surface in a single pultrusion process step, with fiber orientation tailored to the specific loads. The manufacturing feasibility and load-bearing capacity were thoroughly tested and compared with other design and process variants. Approaches to increase stiffness and strength while maintaining good concrete anchorage have been presented and fabricated. Tensile testing of the helical rebar variants with a 7.2 mm lead-bearing cross-section was conducted using adapted wedge grips with a 300 mm restraint length. The new helix geometry variants achieved, on average, 40% higher strengths and almost reached the values of the base material. Concrete pull-out tests were carried out to evaluate the bond properties. The helix contour design caused the bar to twist out of the concrete test specimen. Utilizing the Rilem beam test setup, the helical contour bars could also be tested. Compared with the original helix variant, the pull-out forces could be increased from 8.5 kN to up to 22.4 kN, i.e., by a factor of 2.5. It was thus possible to derive a preferred solution that is optimally suited for use in carbon concrete.


Original languageEnglish
Article number3285
Number of pages19
Issue number15
Publication statusPublished - Aug 2023

External IDs

ORCID /0000-0003-2834-8933/work/142238452
WOS 001045590900001
PubMed 37571179


ASJC Scopus subject areas


  • carbon–concrete composites, helix rebar, pull-out test, pultrusion, tensile test