Analysis of creep properties of bituminous mixture with constant rate of load increment method

Creep properties of bituminous mixture (i.e. creep compliance) is very important to predict rut depth in flexible pavement structures due to traffic loading. Standard creep test is the application of constant stress (or load) to bituminous mixture specimens, and record deformation as a function of time the load applied. There is an alternative to analyse creep based on constant rate of load increment method. There is one additional benefit of this method compared to the standard testing procedure, i.e. creep compliance due to different rate of load increment can be obtained. This rate of load increment can be correlated to the speed of traffic. The experiment is applied to three different bitumen contents (for the same aggregate gradation), i.e. 6.3, 6.8, and 7.3%, three different rate of load increment, i.e. 50, 100, and 150 kg/min, and three different testing temperatures, i.e. 30, 45, and 60 degrees C. The results are enable to see the effect of asphalt content, rate of load increment and temperature to the creep compliance. The results show that gradient of creep compliance to time of loading increases linearly as either bitumen content, and or temperature increases, while it decreases linearly as rate of load increment increases. The higher gradient of creep compliance to time of loading means the mixture is more sensitive to permanent deformation (which causes rut depth).