Modeling the Primary and Secondary Regions of Creep Curves for SBS-Modified Asphalt Mixtures under Dry and Wet Conditions

This study was conducted to model the primary and the secondary regions of creep curves, derived from dynamic creep tests, for dense graded polymer modified asphalt mixtures under different moisture conditions. For this purpose, 96 Marshall specimens containing siliceous crushed stone aggregate with 85/100 penetration bitumen, modified with 4.5% of styrene-butadiene-styrene (SBS) polymer modifier, were fabricated and tested at four different loading frequencies, four different temperatures, and two moisture conditions, dry and wet, with three replicate specimens for each experimental combination. Statistical analyses were carried out on the test results and two approaches were proposed to model the creep curves. In addition, a stepwise method was proposed by which it is possible to estimate the location of the boundary point connecting the primary to the secondary regions of the creep curves. The proposed models were compared to the previous ones, and demonstrated to be more accurate.