Asphalt Concrete Performance Combining Use of Increased Reclaimed Asphalt Content and Warm Mix Additives

Abstract

In developed countries there is a clear shift from new pavement structures to rehabilitation works which usually use the mill and fill method by replacing some of the asphalt layers. This process on one hand creates material which has to be milled and on the other hand requires new material for producing asphalt mixtures which are used back to the pavement structure. To improve the economic efficiency and reduce environmental impacts reuse or recycling are presently supported in elevated extent. To make the highest possible use of reclaimed asphalt rejuvenation is seen as one of the options. On the other hand excessive heating of reclaimed asphalt should be avoided to not overburn the bitumen or even to avoid additional ageing of already aged material. Combining effects of rejuvenation and warm mix technologies seems as an interesting option. In this respect a trial section was designed including 13 different options of warm mix asphalt with 0–50% reclaimed asphalt. The asphalt mixtures differed in amount of used reclaimed asphalt (RA) 0/11 mm (0%, 30% and 50%), the gradation of used paving grade bitumen (50/70,70/100) and warm mix asphalt additives or used techniques. In asphalt mixtures there were used bituminous binders with selected low temperature additive, which have primarily the function of reducing the production temperature, or the benefit in terms of improving the properties of the asphalt mixture, the adhesion improvement (in some cases) and in at least one of the cases the potential for reducing the characteristic odor of asphalt mixtures. Additives based on organo-silanes and different types of synthetic waxes (FT paraffin, amide wax, PE wax) have been used. Additionally foamed bitumen technology was applied as well. The asphalt mix performance was assessed by term of stiffness, resistance to permanent deformation, water susceptibility and thermal induced as well as fatigue cracking. The key findings will be presented by the paper.