# Performance Evaluation of Recycled Asphalt
## 3 Results and Discussions for the RAP Materials
### Strength of RAP Lump  
Figure 7 shows the test results of the strength of the RAP lump with different cement mortar contents, and Figure 8 shows the test results of the strength of the new and old specimens with different cement contents.  
It can be seen from Figure 7 that the regression correlation of the test results is not high, due to the obvious discreteness of the RAP lump. However, it can still be seen that with the increase of the proportion of mortar, the strength of the specimens is obviously improved--that is, the strength of the specimens decreases with the increase of the content of the RAP lump. Extrapolating the regression curve, it can be obtained that when the cement content is zero, the splitting strength of RAP lump is 0.62 MPa. Referring to the current Chinese specification \"Technical Specifi  
Figure 8: Strength of new and old material specimens with different cement content.  
Figure 7: Strength of cement mortar RAP lump.  
Pavement Regeneration 2008\", the specification requires that the splitting strength of emulsified asphalt cold recycled mixture used for the lower layer is 0.5 MPa, so the data we obtained meets and is slightly higher than the specification requirements, to a certain extent, this shows that there is a certain basis for stipulating the cold recycling mixture in the current specification [32]. According to the test results of the specific surface area proportion and strength of the RAP lump in the cold RAP materials, it can be seen that the strength of the cold RAP materials cannot be very high because the strength of the RAP lump in the cold RAP materials is lower and the proportion is high. Therefore, excessive requirements for the strength of cold RAP materials should not be imposed.  
It can be seen from Figure 8 that under the conditions of the same gradation, the same cement, the same amount of cement and the same water-cement ratio, the strength of the specimens prepared with the RAP materials is obviously different from that prepared with the new materials. When the new aggregate is used to prepare the specimens, the strength of the specimens increases linearly with the increase of the cement dose; however, when the old aggregate is used to prepare the specimens, the strength of the specimens shows a significant nonlinearity with the increase of the cement dose, when the cement dosage is less than 2%, the strength of the specimens has a significant increase trend, but when the cement dosage of cement is further increased, the strength of the specimens has an inflection point, which is no longer significantly increased, and the strength of the specimens is stable at about 0.5 MPa. Compared with the 1 MPa of the new aggregate specimens, it is doubled.  
The above test results show that the cold RAP materials are composed of RAP lump, so its strength composition is obviously different from that of hot asphalt mixtures. The inherent Strength of RAP lump limits the strength of the cold RAP materials to a large extent. Therefore, for cold recycling technology, it is not important to put forward too high requirements on its strength, but to obtain excellent comprehensive performance for its strength characteristics, at the same time, carrying out targeted structural design according to its performance characteristics [33].  
Performance and Affecting Factors of Vibratory Compaction Emulsified Asphalt Cold Recycling Mixture