## 2 Cracking Characteristics of CRCPs in Belgium  
Characterization of CRCP's long-term performance is largely determined by the early-age cracks, hence crack induction and patterns are of interest for most highway departments [12]. The elimination of randomness in an early-age crack pattern of CRCP has been a point of research interest among the researchers for a long time. Different crack induction methodologies such as metallic tape insertion and transverse saw-cutting have been tried to induce uniform crack pattern over the designated locations in CRCP. In Belgium, the transverse partial surface saw-cuts at one of the outer edges of the pavement concrete slab within 24 h after concrete pouring is used as the most effective crack induction method for the crack induction in CRCPs. This crack induction method was first introduced during the construction of CRCP sections in the reconstruction project of the Motorway E313 in Belgium. The transverse saw-cuts were made on the outer lane of the pavement within 24 h after the concrete placement. Two saw-cut depths of 60 mm and 30 mm were selected for crack development on CRCP test sections. Crack spacing surveys were conducted on the test sections just after the concrete placement without considering the effect of traffic loading on crack development. To evaluate the effectiveness of this crack induction method to induce the cracks from the desired locations of the concrete slab, the observed crack patterns of these test sections were compared with those of recently constructed CRCP sections without partial surface saw-cuts on the Motorway E17 in Belgium. The composition and properties of the concrete used in the CRCP section along with the instrumentation used are reported in the experimental study [12]. The survey results of the crack developments on the E313 sections with different saw-cut depths are illustrated in Table 2. For the CRCP section with a deeper saw-cut depth (60 mm), all the observed cracks were initiated from saw-cuts during first four days as shown in Figure 1[22]. After a period of about two months, the deeper saw-cut section exhibited 78.6% of cracks over the saw-cuts. While in case of the section with 30 mm saw-cut depth, this valued reduced to 56.5%. It shows that the deeper saw-cut is more effective than the shallower saw-cut in inducing the cracks over the designated locations (tips of saw-cuts) in CRCP [22]. These field observations indicate that the partial surface saw-cuts can effectively induce the cracks within the first two months after the concrete placement. Even in the later age of CRCP, this crack induction method still played an effective role in inducing new cracks as demonstrated in Table 2. The test section with deeper saw-cuts exhibited the higher percentage of crack initiation at the notches in comparison to the test section with shallower saw-cuts, as depicted in Table 2.  
Figure 2 demonstrates the cumulative crack spacing distribution of the crack pattern on the CRCP sections of the Motorway E313 and E17. It can clearly be observed that the section with 60 mm depth saw-cut illustrated a favorable crack spacing distribution than the section with 30 mm depth saw-cut and the section on the E17 [12; 13; 22]. The section with 60 mm depth saw-cut exhibited only 13.3% of total crack spaced less than 0.6 m (closely spaced cracks) and more than 74.3% of cracks within the desirable crack spacing range of 0.6 m to 2.4 m in Belgium. For the section on the E17, about 50% of cracks were spaced less than 0.6 m, and only 27.6% of total cracks within desirable range (0.6 m-2.4 m) were observed. This finding indicates that the 60 mm saw-cut section has a better crack pattern than the 30 mm saw-cut section and the section without saw-cuts on E17. Based on these field observations, it may be concluded that the crack induction in CRCP is quite susceptible to the saw-cut depth. Therefore, the present study aims to evaluate the susceptibility of crack induction in CRCP to different saw-cut depths and saw-cut lengths.