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

23 5

-16000 -14000 -12000 -10000

-16000 -14000 -12000 -10000

0 % RAP & W/C = 0.43 & SCB-2

0 % RAP & W/C = 0.43 & SCB-1

Pure Mode I Mixed Mode I/II PureMode II

-8000 -6000 -4000 -2000 0

-8000 -6000 -4000 -2000 0

Load (N)

Load (N)

Pure Mode I Mixed Mode I/II Pure Mode II

0

-0.1

-0.2

-0.3

0

-0.1

-0.2

Displacement (mm)

Displacement (mm)

Fig. 3. The load displacement diagram for different specimens and different mode of mixity (RAP% =0 and W/C = 0.43).

Figure 4 shows the effect of RAP content on the load-displacement diagram for SCB-1 under pure mode I, Fig.4.a, and pure mode II, Fig.4.b. As the RAP content increased both stiffness and ultimate load decreased in the cases of pure mode I and pure mode II. This observation agrees with the experimental results in Hossiney et al. (2010) and Su et al. (2014), in which they found that the compressive, tensile, and flexural strengths of concrete pavement containing RAP decreased by increasing the RAP content (see Table 1). On the other hand, SCB-1 specimen under pure mode II has an ultimate load higher than that under pure mode I, regardless of the type of material, i.e., RAP%.

-7000

-7000

(b) W/C = 0.43 & Pure Mode II

( a) W/C = 0.43 & Pure Mode I

-6000

-6000

-5000

-5000

-4000

-4000

-3000

-3000

0 & SCB-1 20 & SCB-1 40 & SCB-1 RAP %

-2000 Load (N)

-2000 Load (N)

-1000

-1000

0

0

0

-0.1

-0.2

-0.3

0

-0.1

-0.2

-0.3

Displacement (mm)

Displacement (mm)

Fig. 4. The effect of RAP% on load-displacement curve for SCB-1 specimen: (a) Pure mode I and (b) Pure mode II.

3.3 The effect of W/C ratio and RAP% on the fracture behavior of concrete pavement

One of the main objectives of the present work is to study the effects of W/C ratio and RAP content on the fracture behavior of concrete. The values of mode I and mode II fracture toughness ( K IC and K IIC ) of concrete pavement with different W/C ratios and 0% of RAP predicted from different SCB specimen geometries are shown in Fig. 5. As expected both K IC and K IIC decreased by increasing W/C ratio. Hossiney et al. (2010) and Su et al. (2014) showed the negative effect of W/C ratio on the mechanical properties of concrete pavement containing RAP. All values predicted from SCB-1 specimen are much lower than those predicted from the other specimen geometries. It is worth noting that, Mahmoud et al. (2014) stated that SCB-1 specimen has become a popular tool to determine the fracture toughness of HMA, and it is a very promising development. In the next section, the reliability of each type of specimen geometry for predicting K IC has been applied based on the concept of maximum undamaged defect size ( d max ).