Application of nanoindentation in asphalt material aging and characterization of actual pavement aging

The aging of asphalt pavements has a serious impact on their road performance and service life., Therefore, it is necessary to characterise the aging behaviour of the actual pavement in service. The aging behaviour of asphalt pavements is difficult to characterise accurately due to the macroscopic nature of the aging indicators obtained by conventional testing methods. Nanoindentation (NI), as an emerging microscopic tool, has been increasingly used in the field of asphalt materials. It is necessary to verify the accuracy of nanoindentation in characterising the aging behaviour of asphalt materials. In this paper, a total of ten samples were selected for testing, corresponding to five states of aging for styrene-butadiene-styrene (SBS) modified and matrix asphalt respectively. The effects of aging on the micro-modulus and viscoelastic properties of the asphalt mastic samples were mainly characterised by means of nanoindentation. This is combined with Dynamic Shear Rheometer(DSR) frequency sweep tests and an attempt to establish a relationship between DSR and NI. Macroscopic characterisation of the aging behaviour of asphalt mastic is achieved. On this basis, the aging behaviour of the actual pavement was characterised using nanoindentation. The results show that the creep compliance of the asphalt mastic back-calculated by the DSR complex shear modulus is in good agreement with the nanoindentation creep compliance results. The accuracy of the nanoindentation characterisation of the aging performance is thus verified. The closer the aging of the actual pavement to the road surface the more pronounced the aging becomes.