# Physical and Mechanical Properties of Reclaimed Asphalt
## 5 Conclusions and Future Recommendations  
This study focused on investigating the performance of RAP for use in unbound pavement layers. To this end, an experimental procedure was used to determine the physical and mechanical properties of blends of RAP and virgin aggregates (VA). Laboratory tests included grain size analysis, a modified Proctor compaction test, a CBR test and triaxial repeated load tests to determine M\({}_{\text{R}}\) and deformation properties. This procedure was applied to five different blends: A (pure VA), B (10-90% RAP-VA), C (20-80% RAP-VA), D (30-70% RAP-VA) and E (40-60%). Finally, the following conclusions are drawn:  
Compared to pure VA, the addition of RAP to VA results in a somewhat finer blend, while the gradation and compaction properties of RAP-VA blends are acceptable and within the specified limits;  
The addition of RAP to the blend lowers the CBR value and this reduction reaches up to 50% when 40% RAP is added to VA;  
The value of M\({}_{\text{R}}\) is higher than that of pure VA in all the RAP-VA blends studied;  
All the blends with RAP develop lower permanent deformations than the blend with 100% VA for the same loading history of 1500 cycles. In particular, blend E with the higher percentage of RAP has the lowest deformation value among all the blends;  
Based on the current experimental findings, it seems that selecting RAP proportions up to 40% is a rational approach to develop RAP-VA mixes that are to be incorporated into unbound pavement layers, since the physical and especially mechanical properties of RAP-VA blends are similar or better than natural aggregates.  
Considering all the controversies in the existing literature on the performance of RAP-VA blends, the results of the present study provide guidance on practical issues in the use of RAP materials for pavement construction. However, they are only recommendatory in nature, which means that testing is required each time to define the capabilities of RAP, taking into account local effects and material conditions. This, in turn, could lead to the desired environmental outcomes: reduced energy consumption and GHG emissions, reduced need for RAP stockpiling and reduced construction and rehabilitation costs.  
In practice, the equivalent load cycles over the life of a pavement are much higher, so further investigation is needed to determine the development of permanent deformationsof RAP-VA blends in terms of pavement sustainability. The development of predictive models that take into account various inherent properties of materials, the content of RAP and various simulations of environmental and traffic conditions in the field is another area for future research following other similar studies. It may also be useful to conduct several cycles of a full experimental program for RAP-VA blends with different proportions of RAP to provide a statistical perspective on the behavior of RAP in unbound layers. In addition, further laboratory testing of RAP-VA blends with RAP proportions of 50% or more should be conducted, focusing on a more comprehensive understanding of bearing capacity as expressed by CBR and \(\mathrm{M_{R}}\) tests (taking into account additional aspects such as the effect of RAP particle fragmentation, stress conditions, etc.) and deformation characteristics. This could lead to a more comprehensive and systematic use of RAP in road construction. Finally, it is equally important that future research focus on life-cycle cost analysis to demonstrate the cost effectiveness of these alternative materials, namely RAP, compared to conventional materials.  
Conceptualization, C.P.; methodology, C.P.; testing and analysis, M.T. and C.P.; writing--original draft preparation, M.T. and K.G.; writing--review and editing, C.P., K.G. and M.T. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.