The crumb rubber modified bitumen (CRMB) has been utilized in pavement industries to mainly reduce the environmental impacts of the wasted tires by turning unwanted scrap tires into new bituminous materials. However, the relatively high viscosity compared to the conventional asphalt is the major drawback of the CRMB. The higher mixing and working temperatures are thus required in order to achieve the desired workability of the CRMB. This results in more asphalt fume emission, higher energy consumption, and more harmful working environments for workers. Warm mix asphalt (WMA) technologies have been intentionally developed to lower the manufacturing and working temperatures of the asphalt by reducing the viscosity of the asphalt binder. Many studies suggested that coupling CRMB with WMA additives can promote better working conditions and minimize environmental issues of the CRMB.
In this study, experimental works were carried out to evaluate rheological and performance-based properties of the CRMB containing WMA additives in order to investigate the effect of the crumb rubber modifier (CRM) content and WMA additives (wax-based and chemical-base WMA additives) by using only one dynamic shear rheometer (DSR). The performance of the studied binder at high, intermediate, and low road service temperatures were investigated by performing Multiple Stress Creep and Recovery test, Linear Amplitude Sweep test, and 4-mm Dynamic shear rheometer test, respectively. Moreover, the Fourier Transform-Infrared Spectroscopy and the storage stability test were also performed to investigate the effects of the CRM dosage and the WMA additives on the aging susceptibility and the high-temperature storage stability of the binders. The results show that the incorporation of crumb rubber modifier can clearly improve the overall performance (rutting, fatigue damage, low-temperature thermal cracking resistances), and aging resistance of the asphalt binder in a bitumen-level. The high-temperature storage stability of the CRMB became more stable at the higher dosage of the CRM. Moreover, it was found that the wax-based WMA additive can only enhance the high-temperature rutting resistance but negatively impacted the fatigue and low-temperature damage resistances of both neat and CRM binders. The effect of the chemical-based additive on the neat and CRM binders are different as it improved the performance over the whole service temperature of the neat but lowered the damage resistances of CRMBs. Additionally, the addition of both WMA additives decreased the high-temperature storage stability of the CRMB. ... Read more

The increasing traffic load has led to the use of polymer modifiers in bituminous mixes in order to improve the performance and the durability of the pavement structures. Epoxy is a thermoset material which ensures enhanced fatigue performance and improved mechanical characteristics when used to modify bituminous materials. However, unlike conventional modification techniques, a series of experimental methods have to be conducted to evaluate the chemical- related phenomena occurring during the binder production and their effects on the performance of the epoxy modified bitumen. For this reason in this thesis, the utilization of epoxy modifiers was investigated at binder level.
Initially, the chemical hardening (curing) process of epoxy modified bitumens (EMBs) was investigated by means of Fourier Transform Infrared (FT-IR) spectrometer and Dynamic Shear Rheometer (DSR). Different combinations of hardening conditions for three epoxy modification levels were studied. Properties, such as modulus and viscosity, were utilized to determine the workability of EMB. At the same time, by using the FT-IR spectrometer, the functional groups of EMBs during the chemical reactions were identified for the understanding of polymerization in the epoxy components.
Additionally, the DSR device was utilized to determine the fatigue and tensile strength of EMBs. It was found that, with increasing the content of epoxy modifier, the fatigue life and tensile strength were increased significantly compared to an unmodified binder.
Finally, the age hardening (aging) of EMBs was evaluated at different time intervals. For the simulation of short-term aging on EMBs, a short-term oven aging method (STOA) was used. For long-term aging, simulations were performed in a pressure aging vessel (PAV) under constant pressure and temperature. The results of chemical characterization and rheological properties of the aged EMBs were obtained by using DSR and FT-IR and were compared to the unmodified bitumen.
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