# Physical and Mechanical Properties of Reclaimed Asphalt
## 4 Results and Discussion
### CBR Results  
According to EN 13286-47 [48], a correction to the force-penetration curve may be required before calculating the CBR value for each blend. If the initial portion of the curve is concave upward, which may be due to an irregular surface, a correction is made by drawing a tangent to the curve at the point of greatest slope. In this way, the measurement  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Coefficients** & **Blend A** & **Blend B** & **Blend C** & **Blend D** & **Blend E** \\ \hline
**C\({}_{\text{U}}\)*** & 29 & 40 & 30 & 23 & 23 \\ \hline
**C\({}_{\text{C}}\)*** & 1.24 & 1.225 & 1.87 & 1.64 & 2.07 \\ \hline \end{tabular}  
*C\({}_{\text{U}}\): Coefficient of uniformity, *** C\({}_{\text{C}}\): Coefficient of curvature.  
\end{table}
Table 2: Coefficients C\({}_{\text{U}}\) and C\({}_{\text{C}}\).  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Blend A** & **Blend B** & **Blend C** & **Blend D** & **Blend E** \\ \hline
**OMC** & 6.9\% & 6.2\% & 6.0\% & 6.5\% & 5.9\% \\ \hline
**MDD** **(kg/m\({}^{3}\))** & 2196 & 2130 & 2083 & 2065 & 2041 \\ \hline \end{tabular}  
*OMC: Optimum Moisture Content, ** MDD: Maximum Dry Density.  
\end{table}
Table 3: Results from the modified Proctor test for all blends.  
of penetration begins at the intersection of this tangent with the penetration axis. Finally, the CBR value for a penetration depth of 2.5 mm and 5 mm is calculated using Equation (3), and the final value is the highest of these values. The final CBR values (average values) for each mixture are shown in Figure 5.  
As can be seen in Figure 5, the CBR value of blend A (VA) is 120%, which seems irrational because it is above the upper limit of 100%. However, if the material tested is crushed limestone that is well compacted, CBR values above 100% are not uncommon [51]. Such a material is blend A. In addition, this value may result from the presence of coarser particles under the penetration piston during the test. Furthermore, the addition of 10% RAP to VA leads to a reduction in the CBR value by up to 35%, starting from a CBR value of 120% in the case of pure VA (blend A). This reduction reaches up to 50% when 20% RAP is added to VA (blend B). Beyond that, the addition of RAP does not lead to further reductions, since the CBR values of blends C, D and E are almost the same, ranging from 57 to 65%. The slight differences between blends C, D and E could be explained by the better interlocking of the particles of blend D and/or the coarser material that was under the penetration piston during the CBR test, which depends on the sample preparation. In addition, the decrease in the CBR value due to the addition of RAP to VA can be explained by the nature of the CBR test. It is based on a penetration procedure in a limited area as large as the contact area between the piston and the sample. Therefore, a finer material such as blend B, and especially blend D and E, is not able to resist penetration due to the limited interlocking of the individual particles. In this context, Figure 5 shows that the CBR value generally decreases with the increasing content of RAP.  
Finally, it is worth mentioning that the observed reduction in the CBR value by adding RAP to VA confirms the scientific findings in the international literature related to the presence of RAP in unbound pavement layers [16; 23; 35].