Research on Fatigue Self-healing of Asphalts Modified by Thermoplastic Polyurethane (TPU) with Different Soft Segments

Abstract

Research on asphalt fatigue and self-healing performance can more accurately model the damage and self-healing evolution principles in practical applications. In order to analyze the rationality of evaluation indexes based on rheology to evaluate the self-healing properties of TPU modified asphalt, a dynamic shear rheometer (DSR) was used in this study to perform time, temperature, and frequency sweep tests of TPU modified asphalt for analyzing the fatigue self-healing properties of TPU modified asphalt over a broader range of temperatures and loading frequencies. This method can improve the accuracy of the fatigue failure determination criteria of TPU modified asphalt and clarify the material performance parameters of TPU asphalt modifiers. The results showed that the increase in hard segment content (Ch) and isocyanate radical index (r) can effectively alleviate the decrease in shear deformation resistance of modified asphalt caused by the increase in N (load repetition). Nf50 (the number of loads when the normalized modulus drops to 0.5) is more suitable to evaluate the fatigue life of TPU modified asphalt compared with Np20 (the number of loads when the DER-N curve is offset by 20% deviation from the linear undamaged line) and N2 (the number of load times corresponding to the intersection point of the tangent line of the DER–N fitted curve and the undamaged line). The degree of self-healing will also increase with the increase in Ch and r. Besides, the higher the healing temperature and the healing time, the longer the fatigue life. The effects of the self-healing evaluation index (HI) on the self-healing index of TPU modified asphalt were as follows: healing temperature > healing time > soft segment >Ch >r > degree of damage > degree of aging > degree of self-healing.