Research On The Performances Of Thermal Resistance Asphalt Mixture Containing Calcined Bauxite

In order to reduce the temperature of asphalt pavement, reduce pavement rutting disease, and reduce the city "heat island effect", Calcined Bauxite with the properties of low absorption rate and low coefficient of thermal resistance was mixed into the SBS modified asphalt mixture as coarse aggregate. Through the mixture design, pavement performance test, thermal resistance performance test and multi-level entropy-TOPSIS evaluation model, the research got the following conclusions:(1) Calcined Bauxite with the content of 0%,20%,40%,60%,80%,100% was taken as coarse aggregate volume instead of ordinary coarse aggregate in modified asphalt mixture, mixture ratio design of Calcined Bauxite modified asphalt mixture was carried out. The asphalt mixture design showed that the mixture optimum asphalt aggregate ratio increased with the Calcined Bauxite dosage increased, and the dosage of Calcined Bauxite have certain effect on mixture density, volume index, Marshall stability and flow value.(2) Pavement performance test showed that with the increase of Calcined Bauxite dosage, the asphalt mixture of high temperature stability, low temperature crack resistance both showed a trend of unimodal changes which increased firstly then decreased, and the peak value show up where Calcined Bauxite content is c=80% and c=60%; but the water stability is reduced with the increase of Calcined Bauxite dosage.(3) The thermal resistance test showed that with the increase of Calcined Bauxite dosage, the mixture of thermal resistance and thermal diffusivity both reduce, the content is 20%,40%, 60%,80%,100% of the Calcined Bauxite modified asphalt mixture, which the thermal resistance is ordinary mixture thermal resistance of 71.03%,’60.49%,52.70%,39.05%, 36.57%. Insulation test showed that, compared to ordinary mixture, as an increase of 20% per Calcined Bauxite, the temperature of the top surface pieces are respectively decreased 3.62%, 6.11%,7.92%,9.28%,10.41%, while the temperature of the undersurface drops respectively 6.84%,11.97%,15.04%,17.44%,19.32%. The reducing of the top surface temperature show that Calcined Bauxite weakened the asphalt concrete surface in thermal radiation absorption ability and showed the characteristic just like the shading pavement; The reducing of the undersurface temperature showed that Calcined Bauxite decreases the temperature transfer in pavement structures, has excelent ability of heat resistance. It can reduce the temperature of pavement effectively, and the more the Calcined Bauxite dosage, the cooling effect is better.(4) Entropy-TOPSIS evaluation model is established, including pavement performance and thermal resistance performance for the first-level indicators, which can select reasonable calcined bauxite dosage. Model calculation results show that the comprehensive properties of modified asphalt mixture with the dosage of 80% calcined bauxite are best.