Dynamic Properties Of Rubberized Asphalt Concrete Under Impact Loading

As a widely used engineering material, asphalt concrete usually works in a static loading environment, and sometimes it would be attacked under the action of dynamic loading, such as impact loading or explosion. In the road, asphalt concrete material withstand the slowly-changing quasi-static loading, and often also withstand intense the dynamic impact loading under the process of vehicle moving because of the uneven road surface and increase of speed. In addition, in the conditions of natural disasters, accidents, terrorist attacks or war, road may be attacked by the transient loading which is much larger than the considered design loading, such as impact loading or high stress wave effect. When the material is under high strain rate loading, the properties of material would be affected by the stress wave propagation effects and the impact of inertial effects, etc, and there are great differences form the static or quasi-static mechanical parameters.With the deterioration of world environment nowadays, as a new energy-saving material, the research of rubberized asphalt concrete has been given more and more attentions.Rubber modified asphalt is a type of cementing material which is made by processing waste tires into rubber powder original and adding into asphalt in a certain percentage, then in temperatures of above 180°C conditions full mixing. Rubberized asphalt concrete which is made by mixing rubberized asphalt and mineral aggregate is good at high temperature stability, low temperature flexibility, aging resistance, fatigue resistance, resistance to water damage and other performance. At the same time, rubberized asphalt concrete has a good potential capacity to resist to impact loading because of the presence of rubber.By using split Hopkinson pressure bar (Split Hopkinson Pressure Bar, SHPB) technique, the dynamic mechanical properties of two sets of asphalt concrete material under impact loading action would be studied in this paper. There are ordinary Asphalt Concrete AC-13 and Rubberized Asphalt Concrete RAC-13, Stone Mastic Asphalt SMA-13 and Stone Mastic Rubberized Asphalt SMRA-13 produced by the rubberized asphalt .The impact test of two sets of asphalt concrete have been done under three different temperatures (-20°C, 25°C, 60°C) and three different strain rates (25s-1, 60s-1, 110s-1). By analyzing the stress-strain curves and comparing the dynamic strength and impact toughness of two sets of asphalt concrete, it is studied on that the performance of rubberized asphalt concrete material on the resistance to the dynamic impact loading has been improved.Test results and analysis show that: the addition of rubber into asphalt concrete can significantly enhance the plasticity of asphalt concrete when it is under the action of impact loading. The dynamic strength and toughness of asphalt concrete is the function of temperature and strain rate, the strength and toughness of asphalt concrete material at room temperature of 25°C is higher than that at low temperature of -20°C and high temperature of 60°C. The value of strength and toughness will be monotonically leveled up with the increase of strain rate, the addition of rubber can obviously improve the strength and toughness of materials and the maximum range of increase is more than 200% and close to 200%, respectively. The excellent performance of resistance to impact loading of rubberized asphalt concrete is because of high viscosity of rubberized asphalt and rigid and flexibility contact mode of "stone-rubber particles-stone" in the asphalt concrete. And there exists an optimal value for the addition content of rubber to get the best performance of resistance to impact loading, and in this paper, about 20% addition content of rubber to asphalt is the optimal value.