Evaluating the Effect of Modified-Bitumens Mixing Temperature and Their Surface Free Energy Variations on Moisture Resistance Performance of Bitumen-Aggregates System

The type of asphalt pavement performance depends on its material properties, manufacturing process and implementation. Surface free energy is an important feature of aggregates and bitumen in predicting the performance of asphalt mixture. Surface free energy indicates the amount of bitumen and aggregate adhesion and the energy parameters related to the moisture resistance performance of bitumen and aggregate. In addition, the mixing temperature of modified bitumen, as part of the modified bitumen preparation method, may have an effective role in the final performance of the bitumen and its composition with aggregates. In this article, the effect of modified bitumens with epoxy resin and their preparation temperature on bitumen surface free energy and moisture resistance of asphalt mixtures is investigated. For this purpose, the modified bitumens containing epoxy resin additive were prepared at 2, 4, 6 and 8 percent (w/w) of bitumen at two temperatures of 90 and 130 °C and surface free energy parameters related to moisture sensitivity were calculated. Results showed different performance between various compositions of bitumen and aggregates for different percentages of additive and bitumen preparation temperatures. In bitumen and silica aggregates, modified bitumen with 6% epoxy resin at 90 °C mixing temperature, and in bitumen and limestone aggregates, modified bitumen with 4% epoxy resin, with 130 °C mixing temperature, showed optimum performance in terms of moisture resistance.