Improved Tensile and Bond Properties through Novel Rod Constructions Based on the Braiding Technique for Non-Metallic Concrete Reinforcements

Abstract

Textile reinforcements have established themselves as a convincing alternative to conventional steel reinforcements in the building industry. In contrast to ribbed steel bars that ensure a stable mechanical interlock with concrete (form fit), the bonding force of smooth carbon rovings has so far been transmitted primarily by an adhesive bonding with the concrete matrix (material fit). However, this material fit does not enable the efficient use of the mechanical load capacity of the textile reinforcement. Solutions involving surface-profiled rods promise significant improvements in the bonding behavior by creating an additional mechanical interlock with the concrete matrix. An initial analysis was carried out to determine the effect of a braided rod geometry on the bonding behavior. For this purpose, novel braided rods with defined surface profiling consisting of several carbon filament yarns were developed and characterized in their tensile and bond properties. Further fundamental examinations to determine the influence of the impregnation as well as the application of a pre-tension during its consolidation in order to minimize the rod elongation under load were carried out. The investigations showed a high potential of the impregnated surface-profiled braided rods for a highly efficient application in concrete reinforcements. Hereby, a complete impregnation of the rod with a stiff polymer improved the tensile and bonding properties significantly. Compared to unprofiled reinforcement structures, the specific bonding stress could be increased up to 500% due to the strong form-fit effect of the braided rods while maintaining the high tensile properties.

Development of a highly various warp yarn manipulation system for the fabrication of 2D net-shape non-crimp-fabrics for highly material efficient concrete reinforcements

“…In order to meet the demand for the building industry highly productive manufacturing methods on basis of the multiaxial warp knitting technology are needed. Therefor past research activities focused on the development of additional, modular systems to enhance the multiaxial warp knitting technology such as additional yarn feeding systems, 19 impregnation and consolidation systems, 20 profiling systems, 9,10,21 shaping systems 22,23 and yarn manipulation systems. 24 In order to produce net-shape NCF for concrete reinforcements focus of this study will be on yarn manipulation systems with an outlook on shaping systems.…”

“…For concrete reinforcement, grid-like structures are used due to a better concrete penetration. Hereby recent developments have improved the anchorage and bond behavior of the textile reinforcement structure in the surrounding concrete matrix through profiled 9,10 or loop-shaped 11 structures. Consequently, the bond behavior between the reinforcement structure and concrete could be improved significantly, resulting in a high material efficiency of the textile reinforcement.…”

Current and Future Trends in Textiles for Concrete Construction Applications

“…The novel profiled rovings are able to transmit significantly higher bond forces in concrete, with up to 500% higher bond strength compared with unprofiled rovings (100 N/mm compared with 20 N/mm). Yet they maintain high tensile properties and minimal structural elongation [38][39][40]. The significant improvement of the mechanical properties is realized through a dominant form-fitting effect between the reinforcement roving and the surrounding concrete matrix, on the basis of a stiff and symmetrical roving surface profile in order to enable a constant and high bond force transmission.…”

Experimental Investigation of Beams Reinforced with Carbon 2D-Netzgitterträger Reinforcement

“…In carbon textile reinforcement, carbon fibers are initially produced in the form of filaments. These filaments are then grouped to form yarns or rovings and finally, rovings are then grouped in a specific pattern to form strands [9,10]. The carbon strands are arranged in a mat-like structure to provide specific mechanical properties.…”