Strength size effect in asphalt binders and mixtures at low temperature

Abstract

Low temperature cracking is the prevailing failure mode in asphalt pavements built in cold regions. This phenomenon manifests as a set of surface-initiated transverse cracks which can lead to further damage due to water penetration. Good strength properties of asphalt binders and asphalt mixtures are, therefore, critical for building durable pavements. The current testing methods used to characterize asphalt binder and mixture strength require the use of very expensive and sensitive testing devices and present limitations in the extrapolation of results from laboratory specimens to larger structures such as full scale pavements. In this thesis the strength size effect of asphalt materials is investigated with the aim of addressing the possibility of using a simple laboratory device, called Bending Beam Rheometer (BBR), for performing strength tests on small beam specimens of asphalt binders and asphalt mixtures. Using three-point bending experimental data and size effect theory for quasibrittle materials, the failure distribution of the Representative Volume Element (RVE) of asphalt binders and asphalt mixtures is evaluated, and a RVE substructure model for asphalt mixture is proposed to analyze the strength measurements obtained on small BBR beams. Forward and back calculation procedures are implemented to directly link the statistic parameters of failure distribution of one RVE to the mean size effect curve of structural strength and vice versa. The effect on strength of different cooling media used in BBR is also evaluated.