Marshall and Balanced mix design in determining the asphalt content for hot mix asphalt mixture: A comparative study

In recent years, the disadvantages of Marshall mix design (MMD) approach have mostly been addressed by Balanced Mix Design (BMD) approach. This study aimed to evaluate the two methods in determining the asphalt content (AC) of hot mix asphalt (HMA) mixtures. For this purpose, the six asphalt contents of 3.5 %, 4.0 %, 4.5 %, 5.0 %, 5.5 %, and 6.0 % by mass of the whole HMA mixture are selected to determine the asphalt content (AC) based on the MMD approach. Also, these asphalt contents are used to determine the AC based on BMD approach. The rut depth (RD) and cracking tolerance index (CT index ) are applied as the evaluation indexes in BMD. According to laboratory testing, by applying the BMD approach, the HMA mixture's AC value is 5.3 %, whereas the MMD approach yields 4.7 %. Furthermore, the IDT and CT index values when utilizing the MMD approach were found to be 28 % and 33.4 %, respectively, higher than those of the MMD method. It was concluded that the MMD might not be an appropriate method for designing the HMA mixtures for long-term pavement cracking performance, and these HMA mixtures need to be designed using the BMD method.