PSI - Issue 28

Zuzana Marcalikova et al. / Procedia Structural Integrity 28 (2020) 950–956 Author name / Structural Integrity Procedia 00 (2019) 000–000

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to offer other fiber materials of many various shapes over time (Bekaert, 2020, BASF, 2020), (Koniki and Ravi, 2018, Holschemacher et el., 2010) and the recipe was optimized (Kohoutkova and Broukalova, 2013). Scattered concrete reinforcement in the form of fibers can be divided according to material, surface treatment, fiber shape and shape of the fiber ends. The function of scattered reinforcement is to capture local tensile effects, which are caused by spatial stress in the areas between the aggregate grains. The main reason for the use of dispersed reinforcement is primarily to increase the tensile strength of concrete. Research in the field of testing and description of tensile softening, resp. ductility is described e.g. in the papers (Abrishambafm et al., 2015a, Karihaloo and Wang, 2000, Kurihara et al., 2000) or (Kohoutkova and Broukalova, 2013). Inverse analysis is often used to identify suitable mechanical parameters of fiber reinforced concrete (Sucharda et al., 2018, Sucharda et al., 2015) or special remodeling of experiments (Brozovsky et al, 2009, Sucharda et al 2014). Typical uses of fibers include concrete slabs interacting with the subsoil (Cajka et al., 2020, Kozielova et al., 2020, Pazdera et al., 2019), where the fibers contribute to increased shear resistance. Shear failure in concrete is a very complex problem in concrete (Sucharda, 2020). The shear resistance is primarily affected by tensile strength and fracture mechanical parameters (Marcalikova et al., 2020). In some cases, the dispersed reinforcement is also used to reduce the occurrence of shrinkage cracks, which are caused by volume changes during the maturation of the concrete. This type of reinforcement is most often used in the case of high-strength concrete, which is susceptible to these volume changes. The resulting composite also has other advantageous properties, such as high resistance to the development of micro cracks, high impact strength and resistance to sudden temperature changes. Another advantageous feature is the possibility of manufacturing building elements in various shapes, such as thin walled elements, which could not be made of reinforced concrete, and thus reduce the weight of the structure. Fiber reinforced concrete also has a high durability and still retains part of its strength after exceeding the maximum stresses. All these properties are influenced by the composition of the concrete mixture, the material of the fibers used, their shape, processing fiber reinforced concrete and the amount of fibers used. Load displacement diagram of fiber reinforced concrete with different types of fibers and different dosage compared with load displacement diagram of plain concrete is in the Fig. 1.

Fig. 1. Load displacement diagram of fiber reinforced concrete with fibers with hooked ends and straight fibers according to Marcalikova et al., 2020.

Currently, we can find use of concrete with dispersed reinforcement especially in the construction of industrial floors, foundation slabs (Cajka et el., 2020), or RC beam (Zhao et al., 2018, Giaccio et al., 2008). A design, use and testing of fiber reinforced concrete follows recommendation (DAfStb guidelines, 2011, RILEM guidelines, 2011, di Prisco et al., 2013).