Modelling of Asphalt Mastic in Terms of Filler-Bitumen Interaction

Abstract

ABSTRACT Many studies have focused on modelling the stiffening effect of mineral filler on asphalt binder. However, the interaction between both constituents was always a challenge to address. Current European as well as North American specifications includes limits on stiffening effects of fillers that are mostly empirically driven and hard to include in a mixture design process. This study offers a model that allows estimation of stiffening effects based on primary binder and filler properties. This study builds on a conceptual model provided in an earlier publication for understanding the mechanism by which the filler stiffens the asphalt mastic. The model hypothesizes that change of mastic complex modulus with filler content follows two phases; a diluted phase and a concentrated phase. In the diluted phase, the stiffening effect of the filler on the binder follows a linear filling trend where interaction between filler and binder is minimal. On the other hand the effect of the filler departs from the linear trend once its concentration enters the concentrated phase. The deviation from the linear trend indicates the start of the significant interaction between the filler particles and the asphalt binder. In this study a model is proposed for the effect of mineral filler on asphalt binder complex modulus at given temperature and frequency. The model is defined using three main parameters, (a) Initial Stiffening Rate, (b) Terminal stiffening rate, and (c) Critical filler concentration. The results presented in this study provide measurable filler and binder properties that can be used to estimate these three parameters, which are indicators of the mineral filler interaction with asphalt binder. The model provides an effective tool to determine the role of basic filler and binder physical and chemical properties on the overall complex modulus of the mastic.