Quantification of bituminous mortar ageing and its application in ravelling evaluation of porous asphalt wearing courses

Abstract

Bituminous mortar, consisting of bitumen, filler and fine aggregates (< 0.5 mm), plays a dominating role on the viscoelastic properties of Porous Asphalt (PA), and its ageing is one of the key factors causing the ravelling of PA wearing courses. This research is to quantify the ageing effect on the rheological characteristics of bituminous mortars and apply it in evaluation of the ravelling resistance of PA wearing courses. Bituminous mortars for two types of PA (one with base bitumen and the other with Styrene-Butadiene-Styrene (SBS) modified bitumen) were artificially aged in the laboratory. Cylindrical specimens were then prepared with the aged mortars and their complex shear modulus and shear fatigue life were characterized through the Dynamic Shear Rheometer (DSR) tests. Finite element models containing the structural geometries and material responses of the two PA wearing courses were created. Their stresses and strains under traffic loads were simulated and analysed. The experimental results showed that ageing had more influence on the complex shear modulus of the base mortar compared to the SBS mortar. However, its effects on fatigue resistance are opposite. The numerical modelling results indicated that after ageing, the ravelling resistance of the PA wearing course with base mortar decreased more.