PSI - Issue 5

A.A. Abd-Elhady et al. / Procedia Structural Integrity 5 (2017) 19–26 Mubaraki et al./ Structural Integrity Procedia 00 (2017) 000 – 000

25 7

To check the reliability of the present results, d max has been normalized by the maximum aggregate size (MAZ), i.e d max /MAZ. The values of d max /MAZ are calculated and presented in Fig. 7. Although all values of d max /MAZ are greater than unity, the values of SCB-1 are closest to it and these values range between unity and 2. The values of other geometries are greater than 4 times the MAZ and that is unacceptable; hence, SCB-2 and SCB-3 specimens are unreliable to predict the fracture toughness of concrete pavement containing RAP.

16

SCB-1 SCB-2

(b) W/C Ratio = 0.43

(a) RAP% = 0

SCB-3-1 SCB-3-2

12

8

4 d max /MAZ

0

0.43

0.48

0.53

0

20

40

W/C Ratio

RAP%

Fig. 7. The calculated d max /MAZ from mode I fracture toughness predicted from different geometries of SCB specimen.

The correlation between K IC in the present research predicted from SCB-1 specimen and f fl measured experimentally by Hossiney et al. (2010) of concrete pavement containing RAP with different values of W/C ratio has been made and is presented in Fig. 8. As is already known, the values of f fl and K IC are positive and the extrapolation of the relation between them must go through the origin. In the case of linear relation, correlation coefficient R 2 = 0.885, while, R 2 = 0.994 for a 2 nd order polynomial. The inflection point of a 2 nd order polynomial will occur out of the range of the logical relation, i.e., it will have a negative value. Therefore, it can be concluded that the relationship between the present numerical values of mode I fracture toughness predicted from SCB-1 specimen and the flexural strength measured experimentally by Hossiney et al. (2010) is strongly correlated.

3

y = 0.393x R² = 0.885

0 Mode I Fracture Toughness, MPa  m 1 2

Y = 0.105x 2 + 0.157x R 2 = 0.994

0

2

4

6

8

Flexural Strength (MPa)

Fig, 8. The relation between K IC predicted from SCB-1 specimen and flexural strength of concrete pavement.