Analytical modelling of visco-elastic behaviour of hot-mix asphalt

Abstract

Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.

As part of the revision of the South African Pavement Design Method (SAPDM), laboratory testing was conducted to obtain the dynamic (Complex) modulus |E*| of hot-mix asphalt (HMA) samples. Dynamic modulus gives an indication of linear visco-elastic (LVE) behaviour of HMA materials at different temperatures and loading frequencies; and is required for computation of stresses, strains and displacements in flexible pavement analysis and design. Laboratory tests to obtain dynamic modulus are normally conducted at limited range of temperatures and loading frequencies. In order to characterize HMA mixes for pavement analysis, sigmoidal function master curves are constructed at different temperatures and loading frequencies using a time-temperature superposition principle. Instead of using the sigmoidal function, this paper presents an alternative approach for characterising the LVE behaviour of HMA materials. This approach is based on the use of three rheological models, namely, Burger’s, Huet-Sayegh and the generalised 2S2P1D. The model parameters for all three rheological models were successfully determined. The master curves were developed for all HMA mixes studied. The Cole-Cole and the Black diagrams were determined. Based on the results presented in this paper, the Huet-Sayegh and the Generalised 2S2P1D models appear to predict the LVE behaviour of HMA mixes more effectively than the Burger’s model.