چكيده به لاتين
The rheological properties of bitumen used in asphalt mixtures have a significant effect on the performance of road pavements, which are exposed to rutting, damage caused by humidity, cracks caused by low temperature and fatigue due to traffic and environmental conditions. Also, asphalt is vulnerable to aging due to heat, sunlight, oxygen or a combination of these factors, which leads to the breakdown of asphalt pavement. Therefore, in order to improve the characteristics of asphalt, increase the lifespan of pavements and prevent premature failures by increasing the strength of bitumen and asphalt mixtures, various modification methods such as acid modification, mineral filler modification, polymer modification, etc. is used. In this research, to evaluate the effect of two different types of polymers with different percentages including 5% and 10% thermoplastic polyurethane and 5%, 10% and 15% styrene isoprene styrene in asphalt mixtures that are made using bitumen with a performance grade of PG64-22 and limestone materials are made, it is discussed. For this purpose, various tests such as dynamic creep test at 50°C temperature, Illinois flexibility index test and indirect tensile Cracking Test at 25°C temperature, indirect tensile test in wet and dry conditions, the semicircular bend test has been used at temperatures of 0, -12 and -24 degrees Celsius. The appropriate amounts of using the two mentioned polymers in order to achieve the best performance of the mixtures are obtained by using the simultaneous analysis of the results of performance tests based on balanced mix design approach. The comparison of the mechanical performance of modified asphalt mixtures showed that with the increase in the percentage of polyurethane thermoplastic polymer, the flow number, cracking indices at intermediate temperature and fracture toughness increase and the tensile strength ratio decreases. On the other hand, with the increase in the use of styrene isoprene styrene polymer, the flow number, tensile strength ratio and fracture toughness increase and the cracking indices at medium temperature decrease. Also, the results showed that when two polymers are used together, the flow number and fracture toughness increase and the cracking indices decrease at intermediate temperature compared to the control sample. In relation to moisture-induced damage, in combinations with 5% thermoplastic polyurethane along with 5% styrene isoprene styrene, 10% thermoplastic polyurethane along with 5% styrene isoprene styrene and also 10% thermoplastic polyurethane along with 10% Styrene isoprene styrene, tensile strength ratio has decreased and increased in other compounds. Finally, by using balanced mix design and comparing the performance of the mixtures in the indirect tensile test and the Illinois flexibility index, two compounds T0S5 (0% thermoplastic polyurethane and 5% styrene isoprene styrene) and T5S10 (5% thermoplastic polyurethane and 10% styrene isoprene styrene) were determined as optimal combinations.
