Effects of Recycled Asphalt Material and Natural Pozzolan as Additives of Hot-Mix Asphalt: A Field Study

Using existing resources more efficiently and effectively becomes important currently. The question of how to make the best use of resources arises in the choice between constructing new roads and improving deteriorated existing roads. It is also important to reduce the amount of consumption and cost of materials. This has emerged the need to use waste materials by recycling and reusing. In this study, a new hot-mix asphalt (HMA) mixture was developed using recycled asphalt pavement (RAP), which was obtained by excavating the surface of a road at the end of its service life, together with a waste material namely natural pozzolan (NP). The final obtained mixture was used as a wear layer on an active highway. Core specimens were extracted from the paved layer for one year and subjected to dynamic and mechanical laboratory tests. Adding NP improved the resistance of the HMA mixture under heavy seasonal effects and traffic loads. In addition, NP increased the tensile strength, making the HMA mixture more resistant to deformation than control and RAP HMA mixtures. Dynamic creep test results showed that the control asphalt mixture had the most deformation and that the RAP mixture with NP had the least. According to the laboratory results, NP addition increased the stability value of the control mixture by 40%. Especially in cold seasons, the role of NP was more evident. In the performance tests that were applied on core samples taken from the field, ITS values for September increased by 98%, and the deformation values obtained as a result of the dynamic creep test decreased by 12%. In summary, adding NP to RAP HMA improves the performance of the pavement and the cost-effectiveness of the environmentally friendly use of RAP in HMA.