Adhesion properties of warm recycled mixtures produced with different WMA additives

Eco-friendly, cost-saving and sustainable pavements have become a priority goal due to increased costs of raw materials and strict environmental regulations. To address these challenges, the use of Reclaimed Asphalt Pavements (RAP) and Warm Mix Asphalt (WMA) technologies is becoming more and more frequent in the asphalt industry. Adhesion properties and water susceptibility are major concerns associated with the use of WMA mixtures due to the reduced production temperatures that alter the interaction at the bi-tumen-aggregate interface. The materials response significantly varies depending on WMA technology as well as mixture type. In this sense, this study focused on the evaluation of both open and dense graded mixtures in-cluding RAP and three different WMA additives (organic wax, chemical additive and zeolite). Hot Mix Asphalt (HMA) mixtures were also prepared for comparison purposes. Since raveling (loss of aggregates from the surface layer) is strongly related to the adhesion properties between binder and aggregates, raveling performance were measured by means of Cantabro tests and correlated to the adhesion properties evaluated through Bond Bitumen Strength (BBS) tests. Tests were performed in dry and wet condition in order to assess the water susceptibility. Results showed that the type of WMA technology may influence mixture performance especial-ly when subjected to water conditioning. However, RAP aggregates within both open and dense graded WMA mixtures significantly limited the negative effects of reduced production tem-peratures in terms of adhesion and water resistance. Only the chemical WMA additive guaran-teed performance comparable to HMA, particularly in terms of water susceptibility.