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 – 0 0

24 6

6

6

(b) Effect of W/C on K IIc

(a) Effect of W/C on K Ic

1 Mode II Fracture Toughness, MPa  m 2 3 4 5

1 Mode I Fracture Toughness, MPa  m 2 3 4 5

SCB-1 SCB-2

SCB-1

SCB-2

SCB-3-1 SCB-3-2

SCB-3-2

0

0

0.43

0.48

0.53

0.43

0.48

0.53

W/C Ratio

W/C Ratio

Fig. 5. The effect of W/C ratio on the fracture toughness of concrete pavement without RAP: (a) Mode I and (b) Mode II.

Figure 6 shows the effect of RAP content on the fracture toughness of concrete pavement with W/C ratio = 0.43 predicted from several types of SCB specimen geometries. This figure reveals several points of interest; the values of fracture toughness decrease by increasing the RAP content. Mode I and mode II fracture toughness are dependent on the type of SCB specimen geometry. The same trend was also observed in this figure, i.e., all values predicted from SCB-1 specimen are much lower than those predicted from the other specimen geometries.

6

6

(b) Effect of RAP% on K IIc

(a) Effect of RAP% on K Ic

1 Mode I Fracture Toughness, MPa  m 2 3 4 5

1 Mode II Fracture Toughness, MPa  m 2 3 4 5

SCB-1 SCB-2

SCB-1 SCB-2 SCB-3-2

SCB-3-1 SCB-3-2

0

0

0

20

40

0

20

40

RAP%

RAP%

Fig. 6. The effect of RAP content on the fracture toughness of concrete pavement: (a) Mode I (b) Mode II.

3.4 The reliability of the different geometries of SCB specimen for predicting K IC

The objective of this section is to examine the values of K IC of concrete pavement containing RAP predicted from different geometries of SCB specimen. Sallam and co-workers Al Hazmi et al. (2012), Sallam et al. (2014) and Abou El-Mal et al. (2015) incorporated the materials' properties, i.e., flexural strength ( f fl ) or shear strength, instead of the critical applied stress,  cr , along with the fracture toughness, i.e. K IC or K IIC respectively, of the material to predict the so-called "maximum undamaged defect size ( d max )", instead of the crack length, as follows:

(1)

IC K

Y

a Y f

d



  



cr

fl

max

then

(2)

2

   

   

K

1

fl IC

d



Y f



max

where Y is the geometry correction factor.