Study On The Performance Of Modified Open Graded Friction Course Ofcomposite Phase Change Materials In Seasonal Climate Areas

The extreme temperature changes,large temperature difference between day and night,and many freeze-thaw cycles in seasonal climate areas make traditional asphalt pavement face the problem of road performance attenuation.Asphalt pavement mainly faces the effects of hot and high temperatures in summer,freezing in low temperatures in winter,and freeze-thaw damage and reduced durability caused by alternating between the two.Phase change materials have a special latent heat function of phase change,and their application can effectively alleviate the temperature change of asphalt pavement,but most studies only stay in a single interval of high or low temperature to regulate the temperature of asphalt pavement.In view of the above problems,this paper proposes to use two phase change materials with different phase change temperature ranges,which are applied to the adjustment of high temperature range and low temperature range to control the extreme temperature changes inside the open graded friction course(OGFC).So as to reduce the freeze-thaw damage inside the OGFC,it has certain reference value and application prospects for the extension of the service life of the OGFC in seasonal freeze-thaw areas.Combined with the National Natural Science Foundation of China project "Research on the mechanism of porous asphalt pavement improving the thermal stability of highway embankment on the Qinghai-Tibet Plateau",the heating test,cooling test and freeze-thaw cycle test of various types of composite phase change materials modified OGFC were carried out.The n-tetradecane and paraffin phase change materials were selected and coated with Portland cement slurry to prepare composite phase change materials(CPCM).The temperature control performance of the OGFC and wear layer with CPCM was tested under different environments,and the photothermal effect and heat balance equation of asphalt pavement were used to analyze and study to provide a theoretical basis for the effectiveness of environmental improvement of the OGFC and wear layer under different climatic conditions.Based on the damage mechanics theory and uniaxial compression test,the degree of freeze-thaw damage of CPCM-OGFC was comprehensively evaluated according to the mechanical and physical properties of the modified anti-slip and wear layer(CPCM-OGFC)of composite phase change materials before and after freeze-thaw.The results show that the prepared composite phase change materials(CP46 and CP5)have stable properties,improved thermal stability and water stability,and the performance and volume parameters of the modified OGFC of the composite phase change material are stable.The addition of CP46 in the heating test lowered the maximum temperature in OGFC,and the 5% content of indoor and outdoor tests reduced its internal temperature by about 4°C.In the indoor cooling test,when the CP5 is 5% content,the internal temperature of OGFC is increased to varying degrees,which can melt the thin ice layer on the surface of the OGFC specimen and discharge the surface water in time to prevent the occurrence of secondary icing;CP46 and CP5 are incorporated into OGFC in different proportions,which reduces the heating and cooling rate in OGFC,and the temperature regulation and control range is further extended.In the freeze-thaw test,the incorporation of CP46 and CP5 improved the anti-freeze-thaw damage performance of OGFC,and the anti-freeze-thaw damage effect of CP5-OGFC specimens was better than that of CP46-OGFC as a whole,but the optimal dosage should not be greater than 3%,and it was appropriate between 2%～3%.After CP46 and CP5 were mixed and frozen-thaw for 20 times,OGFC played a temperature damping effect in the freeze-thaw cycle due to the latent heat of phase change of the binary phase transition system in their respective temperature ranges,and CP46/CP5-OGFC had the best anti-freeze-thaw damage resistance of the 2/2 ratio specimen.Combined with the above tests and theoretical model analysis,the three types of phase change graded asphalt mixture can actively regulate the temperature of asphalt pavement,which has a certain effect on improving the road environment,alleviating the freeze-thaw damage inside OGFC and good road performance.