Date

2023-1-27

Author

Özçiloğlu, Mehmet

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Crumb rubber (CR) has long been used in pavement production as it enhances the pavement performance and contributes to recycling scrap tires. However, the performance of CR modified asphalt (CRMA) prepared through the wet process is affected by the modification variables, i.e., CR ratio, CR and asphalt properties, mixing parameters (temperature, duration and rate), and mixing procedure. On the other hand, CRMA preparation procedure is still not standardized yet. This experimental study aims to contribute to the literature and standardization process by thoroughly investigating the effect of two CR modification essential variables, mixing duration and mixing rate, on the intermediate and high temperature performance of modified asphalt. Since the effects of the other variables are mainly known, these variables were kept constant with optimum values based on the previous studies. In order to simulate the current industry and research experiences, CRMA samples were prepared by using a broad range of mixing rate and mixing duration levels. Overall, 24 different CRMA samples were prepared in the laboratory environment either using a low shear mixer or high shear mixer. These asphalt samples were analyzed based on the conventional asphalt tests (Brookfield viscosity test, penetration test, softening point test and resilience test) and performance tests (dynamic shear rheometer [DSR] test). In addition to that, the potential of the use of image-based technologies to characterize modified asphalt behavior is analyzed. For that reason, the sample images (unaged and aged) are captured by fluorescence microscopy and analyzed. Accordingly, it is concluded that modifying asphalt with CR improves the intermediate and high temperature performance such as rutting, fatigue-cracking and aging-resistance. In addition, the effect of mixing rate was observed mainly in the high shearing and lower shearing levels and only in the viscosity and high temperature true grade results. Any significant difference was not observed within the low shear mixing levels. Furthermore, 30 minutes of the mixing duration was not sufficient particularly according to resilience test results. For the rest of mixing durations, the effect of mixing duration on the intermediate and high temperature performance of CRMA was very limited. Therefore, it is suggested to utilize lower levels of low shear mixing if high shear mixing is not particularly demanded and not extensive mixing durations for the CRMA preparation process. Consequently, energy consumption during the CRMA production can be reduced.

Subject Keywords

Crumb, Rubber, Asphalt, Modification, Variables, Rheology, DSR, Mixing, Time, Duration, Fluorescence, Microscopy

URI

https://hdl.handle.net/11511/102080

Collections

Graduate School of Natural and Applied Sciences, Thesis