PSI - Issue 42

Stanislav Seitl et al. / Procedia Structural Integrity 42 (2022) 1512–1519 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1515

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3. Experimental procedures The experiments were done in a laboratory with controlled temperature and humidity. The temperature was set to 23 ± 2 °C and the absolute humidity was kept at 10 g/m 3 (the corresponding relative humidity is 50 ± 2 %). 3.1. Fracture mechanical tests Cubes with the edge of 100 mm were used for compressive strengths tests at the age of 28 days. Prisms 80×80×480 mm were made for the testing of fracture properties. A notch deep ca 27 mm (1/3 of the specimen height) was cut into the beams, 220 mm from the one end of the beam at the age of 28 days. Fracture tests in accordance with Effective crack model (Karihaloo and Nallathambi (1989)) were performed on the notched beam (span 400 mm). The fracture toughness K IC is the main result of these tests. Toughness G c was also computed. Fracture work W F was computed from the load-deflection curve in accordance with RILEM recommendation (Elices at al. (1997), RILEM (1985)). The modulus of elasticity in three points bending on notched beam, E , is the partial result of these tests. After the fracture test, a part of the broken beam, whose length is approximately 260 mm, was used to test the flexural strength f b (span 220 mm).

Table 2. Fracture mechanical properties of concretes with various water to cement ratio in different age.

Volume density

Compressive strength

Bending strength

Modulus of elasticity

Fracture toughness

Fracture work

Mixture

Age

w / c

VD

D max

f c

f b

E

K IC

W F

[days]

[mm]

[kgm -3 ]

[MPa]

[MPa]

[GPa]

[MPam -1/2 ]

[Jm -2 ]

1

0.50 0.40 0.30 0.30 0.50 0.40 0.30 0.30 0.50 0.40 0.30 0.30 0.50 0.40 0.30 0.30

8 8 8 8 8 8 8 8 8 8 8 8

2199 ± 10 2339 ± 11 2347 ± 9 2397 ± 10 2200 ± 6 2332 ± 11 2340 ± 12 2395 ± 10 2191 ± 7 2325 ± 17 2342 ± 12 2389 ± 4 2180 ± 18 2310 ± 19 2347 ± 4 2380 ± 4

8.6 ± 0.3 24.5 ± 0.1 24.1 ± 0.1 25.0 ± 0,4 45.0 ± 0.4 69.9 ± 1.0 78.6 ± 0.7 79.2 ± 0.6 51.0 ± 1.5 77.8 ± 0.5 83.2 ± 3.6 85.3 ± 1.5 49.8 ± 2.7 81.7 ± 1.5 95.3 ± 3.2 91.8 ± 2,7

- - - -

- - - -

- - - -

- - - -

16

28

6.5 ± 0.5 8.0 ± 1.0 10.1 ± 0.4 8.6 ± 0.5 6.8 ± 0.4 8.0 ± 0.4 9.1 ± 0.1 7.9 ± 1.0 7.9 ± 0.5 12.1 ± 0.7 9.6 ± 0.3 -

32.3 ± 2.3 38.3 ± 1.8 39.9 ± 1.4 37.1 ± 3.6 32.0 ± 1.1 38.2 ± 2.6 39.3 ± 2.9 29.7 ± 2.9 39.4 ± 1.1 44.6 ± 2.0 42.1 ± 2.2 -

1.05 ± 0.09 1.29 ± 0.11 1.48 ± 0.09 1.55 ± 0.23 1.19 ± 0.14 1.49 ± 0.08 1.44 ± 0.13 1.10 ± 0.19 1.42 ± 0.18 1.60 ± 0.06 1.78 ± 0.06 -

108 ± 18 153 ± 15 138 ± 5 176 ± 21 116 ± 13 136 ± 5 151 ± 15

16

91

16

-

365

133 ± 13 141 ± 18

16

3.2. Fatigue test Fatigue tests were performed by using three-point bending load on concrete beams (80 × 40 × 240 mm) with a notch of the length a ( a / W = 0.1). Stress ratio R = 0.1 and 10 Hz frequency were applied along the tests, see Zhang et