PSI - Issue 28

Lucie Malikova et al. / Procedia Structural Integrity 28 (2020) 403–410 Lucie Malikova et al./ Structural Integrity Procedia 00 (2019) 000–000

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Fig. 1. Schema of the semi-circular disc with an angled crack loaded in three-point bending.

3.1. Material properties Before the numerical analysis could be performed, experimental measurements on basic fracture mechanical properties had been carried out. The material was manufactured by mixing the ground granulated blast furnace slag from Czech production (Kotouč Štramberk, spol. s.r.o) with Blaine fineness of 400 m 2 /kg and Standard sand with a maximum grain size of 2 mm. The ratios between aggregate and slag was ( a / s ) was 3:1, between water and slag ( w / s ) was 0.45. The of sodium hydroxide activator was 6% of Na 2 O. To maintain the appropriate workability of mortar, the lignosulfonate-based plasticiser was dosed in the amount of 1% by mass of slag. 3.2. Specimen geometry Specimen geometry can be seen in Fig. 1 and the dimensions investigated within the numerical parametric study 3.3. Experimental set-up During the experimental campaign, 6 various geometrical configurations of the SCB specimen were tested. All of them had got the thickness of 20 mm. Particularly, specimens with an inclined crack with  = 30, 40 and 50° and a = 10 and 25 mm were investigated. Note, that 3 specimens of each configuration were tested. The SCB specimens were cast in special silicone moulds with a wooden frame and then stored in the moulds covered with a PE foil for 24 hours. After demoulding, they were stored in the closed chamber with RH > 95% until fracture tests were performed, i.e. until the age of 161 days. Meanwhile, the initial notches were cut by a water jet. Throughout the 3PB test, the specimens were subjected to quasi-static loading with a governed increment of displacement, which was 0.02 mm/min during the whole testing. The dependence between the loading force and the crack mouth opening displacement was recorded with a frequency of 5 Hz. 3.4. Numerical modelling A numerical model in a commercial finite-element software ANSYS was created based on the real specimen geometry and material properties. The model was simplified and a two-dimensional mesh of the cracked specimen was created considering plane stress conditions in order to investigate the crack behavior on the surface of the specimen (for better comparison to experimental data obtained optically from the specimen surface). The supports were modelled via zero displacements in the corresponding directions and the compressive loading force ( P = 1 kN) are as follows:  R = 50 mm  S = 40 mm … … … … specimen radius, half-span between the supports, angle of the inclined crack,   = 10, 20, 30, 40 and 50°  a = 10, 15, 20, 25, 30 and 35 mm crack length.