Creep Stiffness Master Curve of Recycled Asphalt Pavement (RAP) Modified Asphalt Binders Based on Binder Beam Rheometer (BBR) Test Data

摘要

Recycled Asphalt Pavement (RAP) was introduced to the transportation industry to build economical and sustainable pavements. However, thermal cracking at low temperature can increase with the use of RAP in the hot mix asphalt (HMA). Therefore, it is necessary to study the change in creep stiffness (S), which is a measure of the thermal stresses due to the thermal contraction. Higher creep stiffness value indicates higher thermal stresses resulting in higher susceptibility to cracking. Conventional Superpave low-temperature criteria for binder requires only one creep stiffness value from Bending Beam Rheometer (BBR) at 60 sec. The objective of this study is to construct creep stiffness master curve using BBR test data and characterize the low-temperature behavior of the binder due to the addition of RAP. A Superpave PG 58-22 binder was used as the control binder and four RAP percentages in the HMA (15%, 25%, 35% and 40%) were studied at different temperatures and two aging condition were evaluated. Creep stiffness master curves were developed at -12 °C. Results show that increasing RAP percentages and further aging conditions contribute to the increased stiffness of RAP binder blends at low-temperature. Furthermore, the rate of stiffness increase due to aging decreases with the addition of higher RAP in binder. Therefore, aging has less effect on binder with higher percentage of RAP than binder with no RAP.