Abstract:

In low-temperature environments， asphalt concrete pavement is prone to low-temperature cracks， which affect the performance and driving safety of the pavement. To improve the low-temperature crack resistance of asphalt concrete， different dosages of rubber powder are used to modify asphalt concrete. Select relevant raw materials such as asphalt， rubber powder， and mineral powder， and add 5 kg/m³ rubber powder， 15 kg/m³ rubber powder， and 25 kg/m³ rubber powder to asphalt respectively to prepare three different specimens A-1， A-2， and A-3. Adopting AC-13 grading， the mass ratio of asphalt to aggregate is fixed at 7.0%.Conduct a three-point bending test at -30 ℃ to determine the flexural tensile strength， maximum flexural strain， and flexural modulus of the specimen； Calculate the brittleness index based on the load displacement curve within the temperature range of -50 ℃ to -5 ℃ to comprehensively evaluate the brittleness characteristics of materials at different low temperatures； And use scanning electron microscopy to observe the cross-sectional morphology of the specimen at a scale of 10 μm， and analyze its internal pore structure and interface bonding state. The results showed that specimen A-2 with a rubber powder content of 15 kg/m3 had the best comprehensive performance， with a flexural strength of 10.35 MPa， a maximum flexural strain of 4456 μ?， a flexural modulus of 2323 MPa， and a brittleness index below 0.6. The microstructure showed uniform pore distribution， good bonding between rubber powder and matrix interface， and effectively enhanced stress dispersion and deformation coordination ability. This study determined the optimal rubber powder dosage of 15 kg/m3 to improve the low-temperature crack resistance of asphalt concrete through a combination of macro and micro experimental methods. It provides direct and reliable data support and theoretical basis for the design and application of pavement engineering materials in cold regions， and has practical significance for promoting the efficient utilization of waste tire rubber resources in road construction.

Key words: Rubber powder composite modified asphalt, Three point bending test, Brittleness index, Flexural modulus