PSI - Issue 73

Kateřina Matýsková et al. / Procedia Structural Integrity 73 (2025) 100 – 105 Kateřina Matýsková, Marie Horňáková / Structural Integrity Procedia 00 (2025) 000 – 000

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strength were tested and evaluated according to (EN 196-1, 2016). The static modulus of elasticity was determined according to the procedures given in (ISO 1920-10, 2010, pp. 1920 – 10) and the dynamic modulus of elasticity was determined by the ultrasonic pulse velocity method according to the standard procedures given in . The fracture tests were carried out based on procedures according (Karihaloo and Nallathambi, 1990) model of effective crack. Based on the testing performed, the fracture energy, fracture toughness, effective crack length and crack driving force were determined. 3. Experimental results 3.1. Mechanical characteristics The average value of volume density tested on 5 samples was determined as 2400 ± 5 kg/m 3 for CET0 and 2260 ± 15 kg/m 3 for CET100. The average bending strength was determined on 5 specimens as 13.5 ± 1.4 MPa for CET0 and 9.3 ± 0.6 MPa. After breaking the samples during the bending strength test, a total of 10 cubic specimens were produced for compressive strength testing with the result of the average cubic compressive strength as 138.0 ± 6.7 MPa for CET0 and 105.3 ± 3.1 MPa for CET100. The dynamic and static modulus of elasticity was determined by testin g on 3 samples as 54.2 ± 0.9 GPa for dynamic modulus and 48.5 ± 1.2 for static modulus in the case of CET0 and 45.0 ± 1.1 GPa for dynamic modulus 35.7 ± 0.3 GPa for static modulus in the case of CET100. The test results are already mentioned and discussed in detail in the previous article (Matýsková et al., “in a review process”) . 3.2. Fracture tests Fracture tests were carried out on 4 samples, the load-displacement diagrams can be seen in the next section (Fig. 3, Fig. 4). In Fig. 3, where the results of the reference concrete (CET0) are depicted, the curve marked by dotted line was excluded from future calculations due to a possible error during the measurement process. Based on the experiment, the fracture energy, fracture toughness, effective crack length and crack driving force was determined (see Table 1). Based on the results, it can be seen that the effective crack lengths are the same for both concretes, but fracture energy is 10.6% higher for the CET100 concrete, which reflects that the CETRIS particles change the fracture process zone and crack-bridging capacity, so propagation requires more energy compared to natural aggregate. In the CETRIS-based concrete this can be explained by additional energy dissipation mechanisms (such as microcracking and crack deflection around wood – cement particles), which increase the overall fracture resistance.

Table 1. Fracture tests results.

Fracture toughness [Mpam -1/2 ] 1.26 ± 0.10 1.06 ± 0.08

Crack driving force [Jm -2 ] 37.43 ± 8.58 32.87 ± 6.24

Effective crack length [m]

Fracture energy [N/m]

CET0

101.19 ± 9.77 111.92 ± 2.01

0.027 ± 0.001 0.027 ± 0.002

CET100

4. Numerical modelling of the three-point bending test A numerical model of a three-point notched beam bending test was created in ATENA software to determine the fracture parameters (modulus of elasticity, tensile strength and fracture energy) in combination with SARA stochastic software. A 2D model of the experiment was first created, see Fig. 2 (left), which was simply supported and loaded with strain increments at 50 computational steps. Two monitors were placed in the model, one monitor tracks the value of the load applied to the model, and the other monitor tracks the value of the displacement in the middle of the model. The mesh of the test body was set as a quadrilateral with a size of 5 mm, while for the steel plates the mesh was set to a size of 10 mm (Fig. 2, right). To avoid stress concentration at the grid points at the support or loading locations, the model was supported and loaded using steel rigid plates (solid elastic material, E = 200 GPa, μ = 0.3). The material model used for the test specimen was 3DNonlinear Cementitious2 , whose input parameters determined based on the experiments are given in Table 2 and Table 3, the other input parameters have been kept in default setting.