چكيده به لاتين
Due to economic and environmental benefits and lack of energy resources, the use of recycled asphalt materials is increasing. In order to achieve the highest economic efficiency, the use of large amounts of these materials in asphalt mixtures has been considered by researchers. There are many concerns related to the durability and long-term resistance to cracking of hot mix asphalt containing these materials. Freezing and thawing cycles are one of these cases that accelerate the growth rate of cracks and damage to the asphalt layer. Fracture mechanics-based research used in this thesis has been widely used to determine the cracking potential of asphalt mixtures under thermal and traffic loads. In order to evaluate the effect of freeze-thaw cycles on asphalt mixtures performance containing recycled materials, laboratory mixtures are prepared incorporating about 30, 50, and 70% of reclaimed asphalt material, raw limestone materials and soft bitumen. The cracking resistance analysis of the samples at low temperature was done by means of stress intensity factor parameter in the pure and mixed modes I/II, and at the intermediate temperature the fracture energy parameter was used in the tensile mode. The performance of the mixtures has also been investigated through resilient modulus and indirect tensile tests witch are common to evaluate the damages caused by moisture. In the present study, the decreased performance ratio of fracture energy, indirect tensile strength, and resilient modulus parameters of mixtures containing 70% RAP after three freeze-thaw cycles, to a mixture with 30% RAP was 0.8, 1.76, and 0.35, respectively. Which can indicate the proper performance of mixtures with high amounts of RAP material in this study.
