To study and evaluate the adhesion between recycled concrete aggregate and asphalt, the contact angles (CAs) between droplet (water and ethanol) and recycled concrete aggregate (RCA), natural aggregates, and solid bitumen (matrix asphalt, SBS modified asphalt) were tested via the sessile drop method with an optical microscope. The surface free energy was then calculated. The CAs between hot asphalt and RCA and natural aggregates were tested via the hanging slice method. The adhesive energy between asphalt and RCA and natural aggregates were calculated based on the test results of the surface free energy and CAs. Then, the influence of RCA on the water stability and fatigue performance of the asphalt mixture was analyzed by testing the water stability and fatigue properties of hot mix asphalts containing RCA (HMA-RCA) with different aggregates and RCA dosages. The surface energy of the various aggregates and the CAs between aggregates and asphalts were sorted as follows: Granite > RCA > serpentinite > limestone. The surface energy and CA of RCA were very close to that of serpentinite. The adhesive energy between various aggregates and asphalt were sorted as follows: Limestone > serpentinite > RCA > granite. The adhesive energy between RCA and asphalt was also very close to that of serpentinite. The residual Marshall stability, tensile strength ratio, and fatigue performance of the HMA-RCAs were gradually reduced along with the increasing RCA dosage. This effect may be attributed to the fact that the adhesive energy between the RCA and the asphalt was less than that of water and that the asphalt was easily stripped from the RCA surface. Excessive RCA content in the aggregate can lead to excessive porosity of the HMA-RCA. The CAs and adhesive energy between RCA and asphalt showed significant effects on the water stability and fatigue performance of HMA-RCA.

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The objective of this study is to investigate the mechanical behavior and shrinkage resistance of cement-stabilized crushed pebble (CSCP) produced via vibration compaction method (VCM). Ten kinds of CSCPs with two different gradations and five cement contents were produced via VCM. The mechanical properties of the CSCPs, including unconfined compressive strength (UCS), splitting strength (SPS), and resilient modulus (RM), were evaluated. Subsequently, the effects of cement contents, curing time, gradation types, and degrees of compaction on the mechanical behavior were investigated. The dry shrinkage and temperature shrinkage and their influencing factors were also studied. Furthermore, the mechanical properties of CSCPs were compared with those of cement-stabilized limestone and granite. The results show that the mechanical properties of the CSCPs increased linearly with the increase in cement contents and nonlinearly with the increase in the curing period and could be improved by using skeleton-dense gradation and increasing the degree of compaction. A good linear relationship was observed between the UCS and SPS and between the UCS and RM. The dry shrinkage and temperature shrinkage resistance of CSCPs could also be improved by using skeleton-dense gradation. The mechanical properties of the CSCPs were lower than those of cement-stabilized limestone, but slightly higher than those of cement-stabilized granite.

To reduce the temperature of asphalt pavements in summer and improve their high-temperature stability, tourmaline anion powder (TAP) was used as a modifier to prepare modified asphalt, which actively cools the pavement. The effects of different TAP contents on the high- and low-temperature performance of modified asphalt and its pavement cooling performance were studied based on the dynamic shear rheometer, low-temperature bending beam rheometer, and indoor rutting plate temperature difference tests; subsequently, the optimum TAP content was determined. Modified asphalt was used to prepare an active cooling antirutting asphalt mixture, and its pavement cooling performance was verified via outdoor lighting tests. High- and low-temperature dynamic modulus and low-temperature semicircular splitting tests were used to evaluate the high- and low-temperature performance; further, freeze-thaw splitting and immersion Marshall tests were performed to evaluate the water stability of the active cooling antirutting asphalt mixture. The results denote that TAP is useful for improving the rutting factor of asphalt. When the TAP content is 16% of the asphalt material, the maximum cooling value of the surface in laboratory tests becomes 5.9°C. When compared with an ordinary asphalt mixture, the dynamic stability of the active cooling antirutting asphalt mixture at medium and high temperatures increased by 18%–22%. The fracture energy can be increased by 12% at low temperatures. The maximum cooling value of the surfaces in outdoor tests is 7.2°C, and the water stability slightly decreases; however, it still satisfies the specification requirements.