PSI - Issue 73

Robert Jurczak et al. / Procedia Structural Integrity 73 (2025) 45–50 Author name / Structural Integrity Procedia 00 (2025) 000–000

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Based on the presented test results, it can be concluded that the average flexural strength at -2 o C and -10 o C of the reference monolithic mastic asphalt beams is approximately twice as high as that of the beams formed by joining two halves produced at different times. This reduction in strength can be attributed to the rapid cooling of the freshly placed mastic asphalt layer in the contact zone with the previously laid, cold layer (Stefańczyk et al., 2008). According to the author, the strength of such joints can potentially be improved by using infrared heaters. These devices allow the cold edge of the mineral-asphalt mixture layer to be reheated over a width of 100-150 mm, raising the temperature to 80-100°C within a few minutes to a depth of up to 40 mm. Additionally, the joint between the layers can be sealed with a bituminous sealing compound to enhance tightness. Moreover, regardless of the method used to join the old and new mastic asphalt layers (with or without self adhesive tape), both average flexural strength values were at a comparable level, amounting to 4.6 MPa and 4.4 MPa, respectively, at a test temperature of -2°C. Similar trends were observed at the lower test temperature of - 10°C. This result was somewhat unexpected for the author, as significantly higher bond strength was anticipated for joints made using self-adhesive tape. A view of the fractured beams is shown in Figure 3. a b c

Fig. 3. View of fractured beams (a) reference monolithic; (b) without the tape; (c) with tape.

The higher flexural strength observed in the monolithic beams also results from the inherent strength of the aggregate used in the mastic asphalt. This is confirmed by the presence of fractured individual aggregate particles visible in the cross-section of the broken beams. It was observed that, in the case of joints between old and new mastic asphalt using self-adhesive bitumen tape, failure consistently occurred at the interface between the old asphalt surface and the tape. This type of failure is classified as adhesive failure, indicating poor adhesion of the tape to the rough lateral surface of the existing asphalt layer. This finding raises questions about the effectiveness of using self-adhesive bitumen tapes in joint construction. Despite the relatively high initial temperature of the newly applied mastic asphalt, the tape does not sufficiently melt to form an effective bond with the old asphalt layer. 4. Conclusions Analysis of the test results enabled formulation of the following conclusions:  The average flexural strength of the monolithic beams at -2 o C and -10°C was approximately twice as high as the average strength of the beams formed by joining two halves, regardless of whether a self-adhesive bitumen tape was used.  The use of self-adhesive tape does not improve the bond strength between old and new mastic asphalt, which is confirmed by the comparable flexural strength values obtained for the specimens without tape.