Enrico Lorenz

Application of stitch-bonded multi‐plies made by using the extended warp knitting process: reinforcements with symmetrical layer arrangement for concrete

With the development of the extended stitch‐bonding process, an important modification of the production process for stitch‐bonded fabrics was realized. Through the introduction of a lateral shift of the needle bar, the stitch‐bonding process is essentially being changed compared with the working method used before. This has made possible the manufacturing of optimally adjusted textile semi‐finished products for numerous applications in the field of composite material. One such application – the usage of stitch‐bonded fabrics as a textile reinforcement for concrete – is analyzed in this article. It was observed that promising possibilities for the use of the extended stitch‐bonding process result from overcoming the known restrictions during the production with conventional stitch‐bonding machines. A markedly improved quality of textile reinforcement is achieved through the new binding patterns and the free arrangement of the layers. The reinforcement shows a verifiable better bonding behavior than the conventional method. Therefore, it is guaranteed that there is no spalling on the concrete surface at service load, which is an important prerequisite for the practical use of textile‐reinforced concrete.

Strengthening of a Barrel-Shaped Roof using Textile Reinforced Concrete

When reconstructing the Zwickau School of Engineering for use as an IRS Office it became necessary to strengthen a reinforced concrete roof structure more than 100-years of age with textile reinforced concrete (TRC). Compared to other strengthening options, only TRC was able to meet the varied demands of monument and fire protection, the architect, as well as the construction company/contractor, while simultaneously meeting all static standards. The thin TRC layer, made of fine-grained concrete with embedded textile reinforcement, was applied to the roof structure in a total thickness of only 10 to 15 mm.

Efficiency Increase of TRC by Using Textile Reinforcements from the Extended Warp Knitting Process

In practice, there are different possibilities to strengthen load bearing structures by sensible combinations of different materials. The composite material, textile reinforced concrete (TRC) is an effective and very innovative strengthening method. Due to the increased lateral tensile loading, there exists the danger of an early failure by delamination in end anchorages and overlaps, where loads are transferred to the textile reinforcement. This leads to a reduction in the tensile load bearing capacity of the textile in the entire structural member. The crack formation effects, which depend on loading, are substantially influenced by existing bond between fiber and matrix and by the size of the process-related fiber undulations. An improved textile manufacturing method was developed by the Institute of Textile Machinery and High Performance Material Technology in Dresden, Germany, to increase the efficiency of the textile reinforcement. The so-called needle shift technology in the extended warp knitting process considerably reduces the thread waviness (undulations) compared to the standard textile manufacturing method. The article in hand describes comparative tests of the bond and strength properties using textiles manufactured with the standard and the extended warp knitting process. The new developed textile fabrics did not only increase the tensile strength of the TRC specimens but also significantly reduced cracking. The results show that, with the developments in needle shift, a substantial improvement in TRC is possible.