Experimental study of recycled asphalt concrete modified by high-modulus agent

Property characterization of high modulus recycled asphalt concretes modified by high modulus agents based on experimental evaluation and comparison with normal recycled asphalt concretes was performed in this paper. Both normal recycled asphalt concretes and high modulus recycled asphalt concretes with percentages of reclaimed asphalt pavement (RAP) varying from 20% to 60% were prepared for property evaluation including dynamic modulus by simple performance tester (SPT), rutting stability by wheel loading test, moisture susceptibility by Marshall test and indirect tensile test, thermal cracking resistance by three-point beam bending test, and fatigue cracking resistance by four-point beam bending test. It is found that, both RAP and high modulus agents can improve the dynamic modulus and rutting stability of asphalt concrete but jeopardize the thermal cracking resistance and fatigue cracking resistance of recycled asphalt concrete. However, the high modulus agents can enhance the moisture susceptibility of recycled asphalt concrete while the RAP could harm the moisture susceptibility of recycled asphalt concrete. It is also noticed that the high modulus agents can reduce the harmful effects by RAP on the properties of recycled asphalt concrete. Meanwhile, increasing the asphalt content of high modulus recycled asphalt concrete can further improve its moisture susceptibility, thermal cracking resistance and fatigue cracking resistance while keep its dynamic modulus and rutting stability still much better than the normal recycled asphalt concrete. The evaluation results show that the high modulus asphalt concrete have more tolerance than the normal asphalt concrete for negative effects of RAP on the engineering properties. It is more promising to use large percentage of RAP in the high modulus recycled asphalt concrete than in the normal recycled asphalt concrete.