PSI - Issue 17

Piotr Smarzewski / Procedia Structural Integrity 17 (2019) 5–12 Piotr Smarzewski / Structural Integrity Procedia 00 (2019) 000 – 000

11 7

E G

l

(mm)

=

c Ic

(5)

ch

2

f

t

where f t is the tensile splitting strength. The mean results of fracture parameters of HPCs calculated on the basis of Eqs. 1-5 are listed in Table 3.

Table 3. Mean values of fracture properties of HPCs. Mixture F p (kN) K Ic (MN/m 1.5 ) G Ic (N/mm) J Ic (N/mm)

CTOD (  m) 20.50 23.13 22.70 21.83 21.25 20.17

l ch (mm)

CSF0 CSF5 CSF10 CSF15 CSF20 CSF25

5.5 6.4 6.4 6.1 5.9 5.4

1.18 1.37 1.37 1.31 1.26 1.16

0.046 0.060 0.059 0.055 0.051 0.045

0.54 0.60 1.22 1.83 0.79 0.43

43.4 42.2 36.5 35.7 37.5 36.8

There seems to be a tendency that the characteristic length decreases with the increasing compressive strength (see Table 3). The effect of SF content on the characteristic length seems to be pronounced. The results indicate that the presence of 15% SF decreases the characteristic length the most. The variation in the fracture energy with SF content is shown in Fig. 5a. The fracture energy increases with growing SF content up to 5%. It is seen that the fracture energy gradually reduces for HPC with SF content above 5%. Fig. 5b depicts the fracture energy versus the compressive strength.

a

b

Fig. 5. (a) Variation of fracture energy with SF content; (b) Fracture energy versus compressive strength at 28 days.

The calculated mean fracture energy increases from 0% to 5% SF content. Between 5% and 10% of SF content, the value of fracture energy remains almost constant. However, above 10% up to 25%, the energy decreases quite significantly despite the slightly increasing compressive strength. 4. Conclusions HPC specimens were examined for compressive strength, static modulus of elasticity, tensile splitting strength, and fracture energy. The characteristic length, which is a reflection of the HPC brittleness, and other fracture parameters of the material were calculated. The six HPC mixtures that were performed had a water/binder ratio of 0.25, and contained 0%, 5%, 10%, 15%, 20% or 25% silica fume. The specimens were cured in containers with water at 20 ºC. Testing was made at 28 days.