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

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1. Introduction

The optimal usage of recycled materials in pavements and geotechnical applications is one of the main objectives of many researches. Reclaimed asphalt pavement (RAP) is commonly used for several purposes such as hot-mix asphalt (HMA), Ghabchi et al. (2016), in concrete pavement, Su et al. (2014), and as base, subbase or general fill materials, Cosentino et al. (2003). Hossiney et al. (2010) and Su et al. (2014) studied the effect of RAP% and W/C ratio on the mechanical behavior of concrete pavement slab. Table 1 shows their results.

Table 1. Experimental results of Hossiney et al. (2010) and Su et al. (2014) RAP% W/C Ratio Modulus of Elasticity, E , (GPa) Poisson's Ratio, 

Tensile Strength (MPa)

Compressive Strength (MPa)

Flexural Strength (MPa)

0 0 0

0.43 0.48 0.53 0.43 0.48 0.53 0.43 0.48 0.53

28.61 27.09 23.85 19.3 20.4 19.65 12.2 14.82 12.82

0.23 0.23 0.23 0.24 0.24 0.24 0.25 0.25 0.25

3.6

34.39 37.33 27.67 24.29 25.25 22.16 16.96 18.2 15.04

5.26 4.98 4.65 4.22 4.08 3.97 3.17 3.49 3.21

3.35 2.63 2.27 2.69 2.26 1.78

20 20 20 40 40 40

1.9

1.93

Braham et al. (2010) analyzed fracture properties of three asphaltic concrete mixes in the laboratory by using single edge notch beam test. Ozer et al. (2016) used semi-circular bending (SCB) test geometry to measure the fracture toughness of HMA containing RAP. Their results showed a positive correlation between SCB test results and other independent fatigue tests. Many researchers use SCB specimen to investigate mixed mode I/II crack growth behavior, notably Yousheng et al. (2017), Aliha et al. (2010, 2014), Sallam and Abd-Elhady (2012), Ayatollahi et al. (2006, 2008), and Lim et al. (1993). Sallam and Abd-Elhady (2012) concluded that, the site of crack initiation in SCB-1 specimen (see Fig. 1.a) is found at the point of the highest vertical coordinate on the notch surface for different notch inclination angles. They also found that, the development of crack front shape is little affected by the value of mode of mixity and the shape of crack front is still more or less the thumbnail shape. Ameri et al. (2012) obtained different modes of mixity by changing the position of supports and/or the site of pre crack, SCB-2 and SCB-3, as shown in Fig. 1.b & c. The main objective of the present work is to study the effect of RAP% on the fracture behavior of concrete pavement under pure mode I, pure mode II, and mixed mode using the three different geometries of SCB specimen shown in Fig.1. The comparison between the mode I fracture toughness obtained from the different geometries of SCB specimen has been made based on the maximum undamaged defect size ( d max ) concept suggested by Sallam and co workers, Al Hazmi et al. (2012), Sallam et al. (2014) and Abou El-Mal et al. (2015).

Y

P

P

P

X

Z

R

R

R

L

L

b

a

a

a

R

S2

2S

S1

2S

(a) SCB-1

(b) SCB-2

(c) SCB-3

Fig. 1. Three types of SCB specimen to simulate mixed mode I/II crack growth