Mechanical Performance Of Warm Mix Asphalt-Treated Bases Incorporating Recycled Asphalt Pavement

Abstract

The depletion of natural resources, the elevated cost related to the construction and the rehabilitation of pavements, the progressive change of the climate, the high heat and harmful gas emission into the atmosphere are the concerns engineers, academics, scientists and politicians have been addressing. They are co-operating toward finding efficient solutions to mitigate these global issues. Thus, the advent of Warm Mix Asphalt (WMA) incorporating Recycled Asphalt Pavement (RAP) as a long-term solution to partially or totally participating in remediating the problem of global warming, climate change and the preservation of environmental resources has gained prominent interest in certain European countries and Asia, North America and most recently in South Africa. This thesis, therefore, aims to investigate the performances of the control Hot Mix Asphalt (HMA) technology and the WMA incorporating RAP at 15% and 30% through laboratory experiment and numerical modelling. Consequently, the laboratory studies that involve the mix designs, the production and the testing of asphalt specimens were achieved following both the South African and the international standards. The RAP used at 15% and 30% in the WMA contains 0.8 % of 50/70 grade bitumen. The virgin aggregate called dolerite and the fillers used in the asphalt mixture were obtained at the Lafarge Olivehill Crushers site in Bloemfontein. The Sasobit, as well as the 50/70 grade bitumen binder, were collected in Sasolburg. The numerical simulation of the WMA – 15%RAP, the WMA – 30%RAP and the control HMA was achieved through the Finite Element Method (FEM) in the Abaqus computer program and the Layered Elastic Analysis (LEA) in mePADS. The Linear Elastic Analysis (LEA) was adopted not only to validate the results found in FEM but most of all, to justify the preference of FEM over the LEA. The numerical simulation WMA – 15%RAP pavement structures, the WMA – 30%RAP pavement structures and the control HMA pavement structures was to analyse their mechanical responses under repeated loading. The results of the laboratory experiment show that: the control HMA exhibits lower rutting performance than the WMA –15%RAP and WMA – 30%RAP; the control HMA exhibits lower fatigue cracking performance than the WMA –15%RAP and WMA – 30%RAP; the control HMA exhibits lower ITS (stiffness) performance when compared tothe WMA – 15%RAP the WMA – 30%RAP; the control HMA exhibits close Marshall Stability and Flow performance tothe WMA – 15%RAP the WMA – 30%RAP. As far as numerical modelling is concerned, the results show that the control HMA pavement structures exhibit lower rutting and fatigue cracking performance when compared to the WMA – 15%RAP pavement structures the WMA – 30%RAP pavement structures. Overall, the WMA can successfully incorporate RAP at up to 30% and can be utilized for the new construction and the rehabilitation of low to medium-traffic volume roads.