A Model for Asphalt Concrete Modulus Prediction from Basic Mix Variables in Saudi Arabia

The asphalt concrete, being the upper layer in flexible pavement structures, is the most important layer as it largely controls the performance of flexible pavements. Therefore, characterization of bituminous mixes comprising asphalt concrete layers is essential in predicting pavement behavior under different loading and environment conditions. In this study, data on the basic characteristics of bituminous mixtures from 138 mixes was collected from the Ministry of Communications′ (MOC) projects and research reports. The main objective of collecting this data was to select an appropriate model that can be used to predict the bituminous mix moduli from the basic mix characteristics. First, the data was used to investigate the prediction accuracy of several widely used models in order to select the most appropriate one for the Kingdom’s conditions. The ability of all models to predict the modulus of local materials was found to be limited. Therefore, it was decided to develop a new model that suits the local conditions. Regression analysis, using the stepwise procedure was used to develop a model that showed a relatively high coefficient of determination (R2=0.86). The variables selected by this analysis were: percent air voids, percent asphalt absorbed by weight, asphalt viscosity at 70°F, asphalt concrete temperature, percent asphalt by volume of mix, and percent aggregate passing sieve # 200