Evaluation of the effect of Evonic on bitumen surface free energy components and stripping performance of hot mix asphalt

Moisture susceptibility is one of the most common pavement failures which cause by loss of bitumen bonding or bitumen-aggregate adhesion due to the moisture penetration. In this study, the effect of adding Evonic in the amount of 0.1, 0.3 and 0.5 percent of the weight of the binder content to PG 60-70 on stripping performance of hot mix asphalt with silica aggregates was investigated. The stripping performance of bitumen and asphalt mixtures was evaluated by measuring the bitumen and aggregate surface free energy components and also by conducting mechanical tests such as modified Lottman test, resilient modulus, fracture energy and boiling water. Moreover, rutting performance of asphalt mixtures was evaluated by dynamic creep test. According to the tests results, mechanical parameters such as indirect tensile strength ratio (TSR), resilient modulus and fracture energy for conditioned and un-conditioned asphalt mixture specimens made by modified bitumen were increased as well as coating of aggregate-bitumen mixture was increased in boiling water test. Furthermore, specimens made by 0.3 and 0.5 percent Evonic meet minimum moisture susceptibility which control the stripping resistance of the mixtures. Also, adding evocic to bitumen increases the total surface free energy of bitumen, non-polar component of bitumen free energy as well as energy of adhesion between the aggregate and bitumen. Dynamic creep test results show that adding Evonic up to 0.3 percent to bitumen does not change the liquid number, but the adding more percentage of Evonic reduces the liquid number which is negligible.Keyword: Hot Mix Asphalt (HMA), Bitumen Surface Free Energy, Indirect Tensile Strength Ratio (TSR), Rutting, Evonic