Research On Influence Of Ni Ti Phase Change Material On Asphalt Mixtures Performances

Asphalt pavement is often affected by high temperature during its service,such as unheaval,rutting,transposition and other diseases.In order to improve the high temperature stability of asphalt pavement,scholars in the road field began to explore the application of Phase change material(PCM)in asphalt pavement.Applying phase change materials with suitable temperature sequence to asphalt pavement can reduce the temperature sensitivity of pavement,alleviate the high temperature disease of asphalt pavement.However,most of the road phase change materials in the current research are organic materials.The organic phase change material has the problems of reducing the mechanical properties of the asphalt mixture,easily volatilizing and leaking,which seriously affect the temperature regulation effect of PCM and the road performance of asphalt mixture.The alloy phase change material has the characteristics of phase change and no volatilization and leakage.It will not cause the mechanical properties of the mixture to be reduced and the environment will not be polluted by mixing it into the asphalt mixture.Therefore,the alloy phase change material is added into the asphalt mixture to study its mechanism of the temperature modulation and the effect on the performance of the asphalt mixture.It lays the foundation for the application of metal phase change materials in asphalt pavement.The NiTi alloy phase change material(NiTi-APCM)suitable for the stability of the pavement was selected as the research object.This paper studied the thermal properties,mechanical properties and adhesion of the basic properties of NiTi-APCM,optimize the processing technology of NiTi-APCM,It was determined that the NiTi-APCM kept at a temperature of 600°C for 15 minutes has the largest enthalpy and the temperature sequence is suitable.The optimized NiTi-APCM was mixed into asphalt mixture to prepare NiTi-APCMasphalt mixture.The NiTi-APCM-asphalt mixture was tested by rutting test,bending test at low temperature and freeze thaw split test.The results show that NiTi-APCM has a higher hardness,and the adhesion rate is 77.82%.NiTi-APCM improves the high temperature performance of asphalt mixture,lowers the low temperature performance,and has little effect on the water stability.When the replacement rate is no more than 6%,it can meet the standard requirements.The temperature regulating effect of NiTi-APCM on asphalt mixture was studied through indoor temperature adjustment test,outdoor temperature adjustment test and infrared thermal imaging test.The temperature regulating effect of NiTi-APCM was evaluated by calculating the temperature adjustment index.The thermophysical parameters of NiTi-APCM-asphalt mixture were measured,and the specific capacity-temperature curve was fitted piecewise.By means of Wilcoxon signed rank test,it is verified that the measured temperature of NiTi-APCM is not significantly different from the theoretical control temperature.The results show that NiTi-APCM can be used as a pavement phase change material into asphalt mixture to reduce the highest temperature of the pavement.The greater the incorporation of NiTi-APCM is,the better the effect of temperature adjustment,the more temperature accumulates in a certain time domain.Considering the pavement performance,temperature regulation performance and economy,the best replacement rate of NiTi-APCM is 6%.The specific capacity-temperature curve of NiTi-APCM-asphalt mixture increases first and then decreases rapidly in the NiTiAPCM phase transition temperature range.The greater the replacement rate of NiTi-APCM is,the greater the peak value of the specific capacity is,the greater the thermal conductivity of the mixture is.The temperature regulating mechanism of NiTi-APCM was revealed on the basis of the thermophysical parameters and the temperature adjustment test.