چكيده به لاتين
Considering the increasing cost of asphalt mixtures and efforts to improve the mechanical performance of road pavement during the service life, extensive research has been conducted on the use of recycled and waste materials. Crumb rubber is one of the commonly used recycled materials in studies related to modifying the performance of bitumen and asphalt mixtures. Adding this material can change the viscosity and hardness of bitumen, as well as promote settlement and phase separation of rubber from bitumen. Therefore, the aim of this research is to improve the performance of hot mixture asphalt containing crumb rubber, reduce settlement and phase separation of rubberized bitumens, and investigate the interaction between crumb rubber, bio-oil, and waste oils in bitumen and their impact on the mechanical properties of hot mix asphalt, including rutting, moisture susceptibility, and fatigue. The pre-swelling method of crumb rubber with bio-based oils and waste oils is employed to address the challenges of settlement and phase separation of rubberized bitumens. Cigar tube test and Fourier transform infrared spectroscopy are conducted to evaluate the issues related to rubberized bitumen and the interaction between oil and rubber powder. Additionally, a balanced mix design approach is employed to determine the optimal percentage of different oils by conducting dynamic creep tests, Illinois flexibility index, and indirect tensile strength ratio tests. For the preparation of samples, PG64-22 bitumen, limestone aggregate with gradation No. 4 according to publication 234, 40 mesh crumb rubber with the abbreviation CR, one type of bio-based oil, and two other types of oil based on paraffinic oils from the C, H, and M groups are used. The asphalt mixtures are prepared with a constant 15% CR content and varying percentages of oils (5%, 10%, and 15%), denoted by numbers 1, 2, and 3 alongside the corresponding abbreviations. In general, 11 scenarios of asphalt mixtures (hot mix sample, rubberized asphalt sample, and samples prepared with pre-swelled CR with different percentages of oils) are constructed to evaluate the mechanical performance of the asphalt mixtures and subjected to various tests. The results of the indirect tensile strength tests show that CR increases moisture susceptibility, and the combination of oils C and H in a ratio of 1:1 can enhance the indirect tensile strength ratio of the samples. The results of the Illinois flexibility index test indicate that adding CR and oils in low percentages can increase the resistance to cracking at intermediate temperatures. The results of the dynamic creep test demonstrate that the resistance to rutting decreases with increasing oil percentage in the samples, and sample M1 exhibits the highest resistance to rutting among the tested samples. Furthermore, the results of the balanced mix design show that samples M1, H2, C2, and CR cover the acceptable ranges for all three mechanical performance parameters (rutting, moisture susceptibility, and fatigue) among the tested samples.
