This special issue demonstrates the breadth and intensity of ongoing advances in the field of textile reinforced cement composites and the importance of several future research directions. Verification of the structural performance of textile-reinforced reactive powder concrete sandwich facade elements.Appl.
Reinforcing Efficiency of Micro and Macro Continuous Polypropylene Fibers in
Cementitious Composites
Introduction
Effectiveness of the fiber-matrix bond interface in load transfer and propagated cracking in mechanical performance is addressed. Anchorage and bonding are also enhanced by geometric modifications of the surface texture of the fiber [14].
Experimental Program
In both of these cases, the effectiveness of the fiber performance is measured in the context of the fibers bridging the cracks in the cementitious matrix, which subsequently bond and pull out, thus hindering the extension of cracks [15]. The stress transmission through the bridging fibers is an important source of hardening and allows the initiation of new cracks, improving the energy dissipation capacity of the composite material [17].
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- Testing Program 1. Tensile Response of Fibers
- Conclusions
Above point D, the specimen significantly lost its load-bearing capacity and eventually experienced complete failure. Experiments addressed the composite performance of laminates using correlations between fiber-matrix bond, multiple cracks, crack propagation, and crack saturation density. a) Tensile test results and characteristic response regions shown on a typical stress–strain response, (b) four stages of linear elasticity, cracking, multiple cracking, localization and pullout, and (c) interface debonding and pullout contributing to crack propagation. Conflict of interest: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analysis or interpretation of data; in writing the manuscript and in deciding to publish the results.
Mechanical Behaviour of TRC Composites
Mechanical Characterisation and Selection of Base Materials
For each direction of the reinforcement, five uniaxial tensile tests were performed according to the stripping method [20] of Figure 2, obtaining the average peak loads Pmax,avg from Table 5. Referring to the standard deviations (std%) of Table 5, smaller pick distances (fabrics F6 and F7) were generally associated with smaller dispersion of the mechanical results, particularly in the direction of the warp.
Mechanical Characterisation of TRC Composites
In fact, the length of the load application zones in Figure 2, although in the range of the minimum values prescribed by the Italian guidelines [14], is about half of that suggested by recent recommendations for TRC tensile tests [23]. Fabric slippage was most likely to occur in the M2-based composites, as the higher porosity (observed by visual inspection) of the thixotropic mortar penalized the bond between the roving and the cement phase.
Discussion of the Results 1. Effect of Fabric Coating
To better emphasize the effect of the nature of the coating, composites based on M1 alternately reinforced with fabrics F2 and F3 as well as F4 and F5 were considered. In the case of low to medium gram fabrics (F1 and F2), a general increase in the average stress σI-II was observed.
Analytical Modelling
Depending on the value of stress σ applied to the composite, x can be less than, equal to, or greater than 2δ0. Note that each curve in the figures is broken at the loss of the first converter.
Conclusions and Future Developments
Textile reinforced concrete—State-of-the-art report by RILEM TC 201-TRC; RILEM Publications SARL: Bagneux, France, 2006. In Proceedings of the 12th Fib International PhD Symposium in Civil Engineering, Prague, Czech Republic, 29-31. August 2018; pp.
The Impact-Tensile Behavior of Cementitious
Composites Reinforced with Carbon Textile and Short Polymer Fibers
- Materials under Investigation 1. Cementitious Matrix
- Experimental Program 1. Specimens
- Results and Discussion 1. Results of Quasi-Static Tests
- Conclusions
Both the first crack stress and the tensile strength of the composites increase significantly compared to the corresponding values measured in the quasi-static regime. This plateau can be attributed to the pull-out behavior of the textile yarns, as shown in the next section.
Long-Term Durability of Carbon-Reinforced Concrete
An Overview and Experimental Investigations
- Long-Term Durability of Non-Metallic Reinforcement
- Failure Mechanisms of Non-Metallic Reinforcement
- Materials and Test Specimens
- Experimental Investigations 1. Introduction
- Results
- Discussion
- Conclusions and Outlook
The first part of the preload tests is carried out on the long-term test equipment (Figure 3a). The reference load is necessary for specifying preload load levels and long-term durability. Table 3 provides a summary of the long-term durability tests (CLTT—Carbon Long-Term Tests) performed.
Fatigue Behaviour of Textile Reinforced Cementitious Composites and Their Application in
Sandwich Elements
Materials and Methods 1. Material Characteristics
For the manufacture of the sandwich beams, expanded polystyrene (EPS) was chosen as a rigid insulating core. The resulting fiber volume fraction of the specimens was equal to in the loading direction). A more comprehensive description of the working principle of DIC can be found in the literature [32].
Results and Discussion 1. Investigations on TRC Coupons
TRC CYCL 1.0 MPa and TRC CYCL 2.0 MPa were loaded closer to this range, which explains the higher probability of cracking. The fatigue behavior of the sandwich beams depended on the behavior of the TRC surfaces. The evolution of the maximum crack width of SW REF and SW CYCL 1.0 MPa was very similar (Figure 19).
Bond Fatigue of TRC with Epoxy Impregnated Carbon Textiles
Materials and Methods 1. Materials
A small gap between the steel plates acts as a predetermined breaking point in the middle of the sample. To define the load levels of the cyclic tests, the reference strength had to be determined first. It was therefore important that the crack in the middle of the sample developed completely.
Results 1. Reference Tests
To investigate the influence of the load level on the deformation of the specimens, the cyclic creep curves of specimens with the same anchorage length are compared in Figure 7. Comparison of the normalized development of the secant modulus depending on the amplitude (here: anchorage length=3a). Furthermore, the average tensile strength and the range of variation and the reference stresses of the different anchorage lengths are shown.
Summary, Conclusions, and Outlook
In figure 16, the dependence of the textile tension on the anchoring length, which is known from section 3.1, is supplemented with the determined residual stresses. Furthermore, since splitting and fracture occur at the same stresses, the fracture mode does not depend on the value of the residual strength. We would also like to thank solidian GmbH for the free delivery of the carbon textile.
The Effect of Elevated Temperatures on the TRM-to-Masonry Bond: Comparison of Normal
Results 1. Heating E ff ect
Visual inspection of samples immediately after the completion of the heating-cooling regime revealed the formation of fine cracks on the top mortar layer of the TRM coatings. Cracks did not appear to propagate through the entire thickness of the TRM overlays (viewed from the side of the TRM strips). Nevertheless, during drying (especially during heating), a greater amount of moisture escapes from the lightweight mortar compared to the normal weight one, which leads to greater deformations of the TRLM strip due to differential shrinkage and in a longer TRLM shrinkage evolution period.
Discussion
For TRLM overlays, the maximum axial textile stress is reduced by 50% and 36% for specimens subjected to 200◦C with one-layer and two-layer overlays, respectively, compared to the maximum axial textile stress of the reference specimens. Reinforcement of masonry structures with textile reinforced mortar (TRM). Construction. Bond analysis between fabric reinforced cement mortar (FRCM) and concrete strengthening systems.Compos.
Thermomechanical Behavior of Textile Reinforced Cementitious Composites Subjected to Fire
Materials and Methods 1. Matrix
The differences between the geometry, reinforcement and duration of the fire test are shown in Figure 2. Effective depth refers to the level of the most stressed fibers (starting from face 1) during the bend test. Temperature was measured using thermocouples placed on the surface, center, and bottom of the samples.
Results and Discussion 1. Fire-Testing Results
Figure 9 gives a comparison between the load-bearing capacity of untreated and fire-tested samples of series E. Thus, the damage and thus part of the deformation was irreversible (the samples remained curved even after cooling). The same result was observed regardless of the fiber material (glass or carbon), the thickness of the concrete cover (8 mm or 12 mm) and the moisture saturation of the samples (0% or 50%).
Verification of the Structural Performance of Textile Reinforced Reactive Powder Concrete Sandwich
Sandwich Façade Element Concept 1. Sandwich Element Details
As highlighted in Figure 2, this paper focuses on presenting the methods and results related to the local failure (anchoring) and wind load experimental tests, together with the verification of the general behavior and the detailed model of the sandwich element. It is assumed that the dead weight of the element is taken as a vertical reaction force (VE) at the bottom anchors and then transferred through the gusset to the supporting structure. The shear load capacity of the anchors is more difficult to determine through calculations and must therefore be verified through testing.
Materials
For the sake of obtaining the design criteria, the shear capacity of the anchors was experimentally measured in this project, as further explained in Section 4.1.1. The first crack then apparently occurred when the concrete's tensile strength (3 MPa) was reached. The composite action between the TRRPC element covers was improved by incorporating GFRP board-like fasteners.
Methods
Both covers contain two carbon textile grid layers, placed symmetrically in the center of the covers. In addition, the numbers presented correspond to the most exposed parts of the building (worst case). Verification to the ULS corresponds to the failure of the elements and relates to human safety.
Experimental Results of Element Tests 1. Anchor Shear Load Capacities
For the element in this study, the more restrictive limit according to [33] corresponds to a maximum deflection of mm. The performance of the member is analyzed according to the resulting mid-span deflection of the member in correlation with the applied wind load on the exterior (ie, facing the interior of the chamber). In Figure 12, the global behavior of the two tested elements, namely single (S) and double (D) connector configurations, is shown as the wind load versus the mid-span deflection (at locations 1-3 in Figure 8).
Numerical Results
For SLS, maximum displacement, umax, internal liners and liner crack indication are given for WSLS. Consequently, the behavior of the element with a connector spacing of 1.0 m is somewhere in between these two options. In Proceedings of the Eleventh Conference on High Performance Concrete (11th HPC) and Second Conference on Innovation in Concrete (2nd CIC), Tromsø, Norway, 6–8 March 2017.
Validation of a Numerical Bending Model for Sandwich Beams with Textile-Reinforced Cement
Materials and Methods 1. Textile-Reinforced Cement
The critical fiber volume fraction must be exceeded in order to produce the strain-strengthening behavior of TRC. The TRC sides of the sandwich beams were tested with a tensile test based on the recommendation of RILEM TC 232-TDT [26]. The load-deformation behavior of the sandwich sections was investigated by means of a four-point bending setup.
Numerical Model Definition 1. Material Definition
Six elements were stacked over the thickness of the faces and twelve over the thickness of the core of the sandwich beam. Multiple elements were needed across the thickness of the faces to estimate the stress/strain distribution over the thickness. To simulate the bending behavior of sandwich beams, two solids and planes of symmetry were used.
Results and Discussion
Both the tensile strain of the tensile surface and the shear strain of the core are shown in Figures 16 and 17. A comparison of the experimental and numerical strains in the tensile surface of the TRC is shown in Figure 18a. The tensile strain of TRC was taken in the lowest layer of the tensile surface v.
Shear Capacity of Textile-Reinforced Concrete Slabs without Shear Reinforcement
Experimental Investigation on Shear Capacity 1. Test Setup and Instrumentation
