Issue 30

V. Veselý et alii, Frattura ed Integrità Strutturale, 30 (2014) 263-272; DOI: 10.3221/IGF-ESIS.30.33

marked as T31, T39, T86, and T88. The test specimens A, B, and C were provided with notches of relative lengths,  0 , approximately equal to 0.25 1 , 0.33 and 0.50 respectively. The pre-dried surface set was tested at the age of 1 year. The loading span, S , of the three-point bending testing configuration was set to 380 mm. Individual dimensions of the tested specimens, their weight and moisture content are given in Tab. 1.

W [mm]

B [mm]

S [mm]

L [mm]

a 0

M [kg]

#

part

[mm]

 

 [%wt.] 

= a 0

/ W

Pre-dried Surface Specimens

A B C A B C A B C A B C A B C A B C A B C

100.09 100.14 100.21 100.15 100.10 100.04 100.06

26.54 27.77 30.82 24.69 24.62 24.89 26.33 26.44 29.17 29.55 29.81 32.96 99.62 29.77 31.46 25.74 27.90 26.52 29.30 29.02 32.21

380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380 380

400.77 400.67 400.63 400.39 400.46 400.50 400.01 399.93 399.93 400.47 400.31 400.20 400.15 400.10 400.01 399.79 400.03 400.05 400.78 401.44 401.62

9.52

0.095 0.297 0.504 0.098 0.301 0.494 0.084 0.289 0.501 0.256 0.320 0.487 0.255 0.312 0.479 0.248 0.328 0.497 0.244 0.330 0.493

2.756 2.493 2.756 2.268 2.184 2.141 2.332 2.369 2.597 2.987 2.702 2.643 2.807 2.324 2.563 2.384 2.599 2.629 2.967 2.579 2.68

8.16 6.47 5.80 5.80 6.98 7.24 6.70 6.57 5.77 8.95 7.50 7.10 8.73 7.73 7.56

T1

29.70 50.48

9.80

T63

30.12 49.38

8.41

T69

99.89 99.83

28.88 50.00

Wet Surface Specimens

100.09 100.11 100.25

25.62 32.07 48.85 25.44 31.05 47.72 24.86 32.84 49.84 24.44 33.09 49.44

T31

99.62 99.54 99.57

T39

100.14 100.21 100.20 100.22 100.29 100.21

*4.57 *4.06 *4.01

T86

8.26 7.06 6.76

T88

Table 1 : Specimen dimensions, values of relative crack length, mass and moisture.

Fracture testing Specimens were loaded under control of displacement of the upper jaw at the rate of 0.5 mm/min using Heckert FP 10/1 testing machine. The loading force and the doubled mid-span deflection were recorded using the fixture enabling the pure beam deflection reading, see Fig. 1b).

1 It was observed during the fracture testing of the first set that the behaviour of specimens with the shortest notches was accompanied with a part of a fast unstable regime where the structural response was not recorded. These parts of the load–deflection diagrams were then reconstructed/approximated. This observed phenomenon is linked to the insufficiently low stiffness of the used testing device. Therefore, deeper notches (causing lower stiffness of the specimens) were used in the second set.

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