Low Temperature Testing of Ontario Hot Mix Asphalt and Rheological Testing of Recovered Binder

Abstract

This thesis discusses and documents findings from an investigation of low temperature testing of asphalt mixes and rheological testing of binders. A number of asphalt mixes from the different Ontario Ministry of Transportation (MTO) and the City of Kingston construction contracts were investigated for their compliance with conventional Superpave® test methods such as indirect tensile test (IDT), dynamic shear rheometer (DSR) and bending beam rheometer (BBR) as well as additional specification tests such as extended BBR and double-edge-notched tension (DENT) test. To investigate the presence of polymer additives and waste engine oil in the binder X-ray fluorescence (XRF) and infrared spectroscopy (IR) tests were conducted. The American Association of State Highway and Transportation Official’s Mechanistic-Empirical Pavement Design Guide (AASHTO MEPDG) software was used to predict long term low temperature performance of the mixtures in various regions of Ontario. The quality and durability of the binders recovered from some mixes were determined. Quality means the capacity of asphalt binder to reach a set of specific properties whereas durability is the measure of how well the asphalt resists change from its original characteristics when exposed to normal weathering and aging. Tested contracts from the City of Kingston showed grade excesses when stored isothermally for three days at low temperatures according to Ontario’s extended bending beam rheometer (BBR) protocol (LS-308) whereas most of the MTO contracts showed grade deficits. Few of the studied recovered asphalt samples showed deficient strain tolerance as measured in Ontario’s double-edge-notched tension (DENT) test (LS-299). The City of Kingston samples showed predicted times to failure from 9 to 15 years or greater whereas most MTO samples resulted in predicted times to failure of 1 to 5 years. X-ray fluorescence and Fourier transform infrared spectroscopy (FTIR) indicated that most of the samples designed according to MTO specifications included waste engine oil and/or oxidized residues, both shown to reduce the performance of asphalt.