Characterisation of warm recycled porous asphalt mixtures prepared with different WMA additives

The use of Reclaimed Asphalt Pavement (RAP) into new asphalt mixtures and the reduction in the production temperatures by means of Warm Mix Asphalt (WMA) additives are two recognised solutions for sustainable pavements. Despite their environmental advantages, the reduced production temperatures of WMA mixtures may lead to rutting and moisture susceptibility issues. Such concerns need to be properly investigated, particularly in case of porous asphalt mixtures (PA) due to their low durability and high water sensitivity. The objective of this study is to evaluate the feasibility to reduce the production temperature of recycled PA including 15% of coarse RAP aggregates; three different WMA additives were selected (organic, chemical additive and zeolite) to produce PA mixtures at 130 degrees C. One HMA mixture was also prepared at 170 degrees C and an additional WMA mixture was prepared at reduced temperature without any WMA additive for comparison purposes. The experimental programme focused on compactability and durability properties of the PA mixtures. Results highlight the issues related to the reduced production temperatures of PA mixtures, particularly in terms of moisture susceptibility. Only the presence of the chemical additive in the mixture ensures adequate water resistance, although it does not guarantee short-term performance comparable to the HMA mixture.