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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the most optimal method for joint construction. A properly executed joint ensures a durable and monolithic structure. In contrast, if the bonding between the joined materials is inadequate, the integrity of the entire layer is compromised, leading to significantly accelerated deterioration. The aim of the study was therefore to assess the strength of the bond between previously laid mastic asphalt and newly applied asphalt, both with and without the use

of self-adhesive joint tape. 2. Materials and methods 2.1. Mastic asphalt mixture

The starting point for evaluating joint quality in the laboratory was mastic asphalt sampled during the construction of a protective layer on the ES-119 viaduct, as part of the Koszalin and Sianów bypass project, between km 6+400 and km 14+300. The coarse aggregate used in the asphalt mix was sourced from the melaphyre quarry in Grzędy, while the fine aggregate consisted of a blend of crushed sand from the same quarry and natural sand produced by the "Zagórki" plant. The filler material was supplied by Lafarge. The binder used was a polymer modified bitumen 25/55-60 manufactured by Lotos Asfalt. The bitumen content in the mastic asphalt, determined by extraction, was found to be 7.2% (European Committee for Standardization, 2020). Additionally, the permanent deformation resistance of the mastic asphalt was assessed using the static indentation test. This test was conducted in accordance with standard (European Committee for Standardization, 2020), using cubic specimens with 70.7 mm edges. During the test, the specimen remained submerged in water at 40 o C. The average static indentation was 1.4 mm, and the average increase in static indentation after additional 30 minutes of constant load was 0.2 mm. Based on the obtained results, it was concluded that the tested mastic asphalt meets all technical specifications outlined in the relevant requirements (Generalna Dyrekcja Dróg Krajowych i Autostrad, 2014) and is suitable for use in protective pavement layers on engineering objects. 2.2. Methods The bond strength between previously laid mastic asphalt and newly applied asphalt was evaluated through flexural tests on small-scale specimens at temperatures of -2°C and -10°C. Prior to testing, the samples were thermostated for 12 hours at a temperature 1°C lower than the target test temperature. Flexural strength was determined in accordance with the procedure described in standard (European Committee for Standardization, 2016). The tests were conducted using a universal testing machine Walter+bai equipped with a head suitable for three-point bending. The machine was integrated with a computer running the ProteusMT application for test control. Testing conditions were adopted to match those used in the evaluation of cement mortars. The loading rate was set to 50 N/s, and the span between the supports was 100 mm. The specimen preparation process consisted of two stages. In the first stage, twelve halves of prismatic beams with dimensions of 40 mm × 40 mm × 160 mm were cast using mastic asphalt. In the second stage, a self-adhesive tape was applied to the cross-sectional face of six beam halves. These were then placed into steel molds and completed with fresh mastic asphalt. The remaining six beam halves were joined with new mastic asphalt without the use of tape. In practice, according to the requirements (Generalna Dyrekcja Dróg Krajowych i Autostrad, 2014), bituminous tapes with a thickness of 10 mm should be used. However, in the tests, due to the small dimensions of the specimens, a self-adhesive bituminous tape with a thickness of 5 mm was used. The height of the tape was 40 mm. As a result, two sets of full-sized prismatic beams 40 mm × 40 mm × 160 mm were produced: one set of six beams with the self-adhesive bitumen tape at the joint and another set of six beams without tape. To simulate real world conditions associated with the "hot to cold" jointing method, the steel molds and beam halves were not preheated. This led to difficulties in forming a proper mastic asphalt structure, due to accelerated cooling in areas in contact with the steel mold walls. This phenomenon is visibly apparent on the side surfaces of the specimens, although it is confined to the outer layer. Additionally, reference beams were prepared as monolithic specimens, cast entirely in a single operation using mastic asphalt.