PSI - Issue 17

Michal Vyhlídal et al. / Procedia Structural Integrity 17 (2019) 690–697 Vyhlídal et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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• Ratio = 0 / should be in the range of 0.2 – 0.6.

Fig. 1. Specimen geometry and three-point bending (3PB) fracture test configuration.

3.1. Materials and specimens

Due to the dimensions of the test specimens and the need for their compaction, the concrete was prepared from a fine-grained cement-based composite mixture consisting of Portland cement CEM I 42.5 R from the Mokrá cement plant, standard quartz sand with a maximum grain size of 2 mm and water. The ratio was 3:1:0.35. To increase the processability of the fresh mixture, the superplasticizer SIKA SVC 4035 was used at an amount of 1 % by cement mass. The individual components were mixed under laboratory conditions at the Institute of Chemistry (CHE), Faculty of Civil Engineering, Brno University of Technology (FCE BUT) under the supervision of Associate Professor Pavel Rovnaník using an automatic laboratory mixer. The moulds with compacted fresh mixture were sealed with thin PE foil and stored under stabilized laboratory conditions for 3 days. After this period, the specimens were stored in a water bath for until testing. After 28 days, the specimens were removed from the water bath, provided with an initial central edge notch with the depth a 0 = 12 mm by diamond blade saw and subjected to fracture testing in three point bending at the AdMaS research centre operated by FCE BUT under supervision of Dr. Barbara Kucharczyková and Ing. Iva Rozsypalová. See Vyhlídal et al. (2019) for more details.

3.2. Fracture tests

The fracture tests were carried out on a LabTest 6-1000.1.10 multi-purpose mechanical testing machine. The incremental displacement loading of the specimen was performed and F – CMOD (force vs. crack mouth opening displacement) diagrams were recorded.

4. Numerical model

A simplified 2D model was created in Ansys software. Plane strain condition were adopted. The geometry corresponds to the real specimen’s dimensions and boundary conditions, see Fig. 2. Materials were modelled as linear, elastic and isotropic, which are represented by their elastic constants, i.e. Poisson’s ratio ν and Young ’s modulus E (Table 1). In order to determine critical value of tangential stress ̅ θθ,c one more material parameter – fracture toughness K I,c – is required (Table 1). See Vyhlídal et al. (2019) for more details.

Fig. 2. Simplified 2D model of the cracked specimen created in software ANSYS.