Experimental caracterization and multi-scale modeling of the linear viscoelastic properties of aged asphalt concretes

Abstract

RILEM ageing procedure allowing to simulate in laboratory in short time the ageing that usually occurs between 5 and 10 years in asphalt pavement in-situ is used to prepare aged asphalt concrete (AC) specimens. Four accelerated ageing durations (0, 3, 6 and 9 days) are considered to simulate the long-term ageing (LTA). The bitumens of the aged AC are extracted and then characterized. Their shear modulus |G*| and phase angle φ  are measured from -20°C to 80°C  at different frequencies and calibrated with the well-known 2S2P1D model. The parameters of the latter are used as input data in a multi-scale model. This model relies on three scales: the mastic scale (bitumen + fillers smaller than 63 µm), the mortar scale (mastic + sand smaller than 2 mm) and the AC scale (mortar + coarse aggregates from 2 to 10 mm coated with thin bituminous mastic). Its implementation combines Mori-Tanaka scheme (adapted to a matrix/inclusion medium) at both mastic and mortar scales and a self-consistent scheme (adapted to a disordered medium) at the AC scale with a possible contact between the coarse aggregates necessary to well predict the moduli of AC at high temperature and low frequency. Based on the rheological properties of the bitumen and aggregates and the volume fractions of the constituent materials, the multi-scale model allows to predict the stiffness moduli (|E*|) and the phase angle of the AC at each ageing level. The predictions of the multi-scale model agree with the measurements over a wide range of temperatures and frequencies.