Mechanical properties of warm-mix asphalt concrete containing different additives and recycled asphalt as constituents applied in real production conditions

This paper compares several warm-mix asphalt (WMA) blends and hot mix asphalt (HMA) in terms of their resistance to permanent deformation (wheel-tracking tests), fatigue performance and stiffness modulus (four-point bending tests), and water sensitivity (indirect tensile strength ratio). The first stage of the study included the production of Marshall specimens in laboratory to evaluate stability and flow of the blends' specimens as well as their volumetric properties, aiming to select the most promising to apply in the field. WMA technologies involved the addition of four different products: a chemical surfactant, an organic wax, a chemical surfactant combined with cellulosic fibres and organic wax embedded in cellulosic fibres. One WMA blend incorporated 35% of reclaimed asphalt pavement (RAP). The second stage of the project involved the construction of trial sections in the field with plant-produced mixtures, laid and compacted with conventional equipment. Laboratory performance testing was carried out on specimens collected from the trial sections. The results showed that the level of mechanical performance of WMA was, globally, satisfactory and similar to the obtained for the HMA used as reference. Nevertheless, the warm-mix with surfactant additive revealed high sensitivity to temperature. The blend with RAP suffered some influence from the variation of binder quantity added by the RAP. The construction process in real production conditions proved to be feasible.