Two sampling methods (bulk sampling method and stack sampling method) were selected to obtain the RAP samples. The Marshall method was used to design the mix proportion of regenerated asphalt mixture with different contents of RAPs. The performance and its variability of different regenerated asphalt mixtures were analyzed by the rutting test, low-temperature tensile test, immersion Marshall test and the freeze-thaw splitting test. Results show that the RAP obtained from the stack sampling method exhibits an improved effect on the low-temperature crack resistance and water stability of regenerated asphalt mixture in comparison with the RAP obtained from the bulk sampling method. The stack sampling method can reduce the performance variation of the regenerated asphalt mixture than the bulk sampling method.
Five different RAPs were selected to perform gyratory compaction test at different testing temperatures (60 ℃ and 110 ℃) and compaction speeds (0.5 mm/s, 1.5 mm/s, 2.5 mm/s and 3.5 mm/s). The mechanical parameters (stress and strain) were recorded through AFG2 PINEPAVETM which was incorporated into the gyratory compactor. Results show that the stress and strain increase gradually with the compaction of RAPs. Different RAPs exhibit diverse stress and strain values under different temperatures and speeds of gyratory compaction. However, the changing rate of strain is almost the same with regard to different RAPs. The properties of RAP can be indirectly reflected based on these mechanical parameters, which is helpful for the evaluation of RAP performance and design of regenerated asphalt mixture.
The conductive road materials are of great help for the development of intelligent road system. The graphite with different volume contents (0%, 15%, 25%, 35%, 45%) was used to prepare conductive asphalt mixture. In order to enhance the electrical conductivity of graphite modified asphalt mixture, the metal electrode was imbedded into the graphite modified asphalt mixture. The influence of graphite content and electrode on electrical conductivity of graphite modified asphalt mixture was evaluated through electrical resistance sensor (Keithley 6510 data acquisition system). Results show that the electrical conductivity of the graphite modified asphalt mixture increases when the content of graphite rises. The addition of electrodes can effectively increase the electrical conductivity of graphite modified asphalt mixtures within proper content of graphite.
Intelligent compaction technology is a new pavement compaction control technology. In order to research the reliability of intelligent compaction technology for compaction degree evaluation of asphalt pavement, the intelligent compaction technology was used to compact the asphalt mixtures of Ji-shuang highway project (SMA-13 for upper layer of the pavement and AC-20 for middle layer of the pavement). The vibrating compaction value (VCV) was detected by the intelligent compaction system continuously during the rolling process. Then the compaction degree of the two pavement layers after the last vibration rolling was measured by the non-nuclear density gauge. Finally, the relationship between VCV value and compaction degree of the two pavement layers was fitted by the least square method. Results show that the compaction uniformity of asphalt pavement is good through intelligent compaction. The VCV obtained from the intelligent compaction has a good correlation with the compaction degree.
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