冻融条件下相变沥青混合料的低温抗裂及调温性能

Low Temperature Anti-cracking Performance and Temperature Regulating Properties of Phase Change Asphalt Mixture under Freezing-Thawing Conditions

为研究相变材料对温拌沥青混合料的低温抗裂性影响规律及其低温调温性能,采用低温劈裂试验、约束试件温度应力试验、核磁共振技术、差示扫描量热法进行表征,并实测了试验路段面层温度。结果表明:相变材料在升降温过程中均能很好地实现吸热放热,通过焓值对比发现其在降温过程中的调温效果更加明显;根据试验路段现场测温可知,相变沥青路面比普通沥青路面高6℃左右,降温开始时间延迟了60 min左右。而随着相变材料掺量的增大,相变沥青混合料的劈裂强度降低,冻断温度和转折点温度升高,孔隙率增大,这都降低了沥青混合料的低温抗裂性。相关性分析表明,孔隙度与低温劈裂强度、冻断温度和转折点温度的相关系数都在0.97以上,各指标紧密关联。可见,将相变材料掺入沥青混合料能够有效提升沥青路面内部的温度,但会对沥青路面的抗裂性能造成一定的负面影响。同时,冻断温度和转折点温度的Logistic曲线拟合发现,当相变材料掺量为3‰时,沥青混合料的强度既能保证规范要求,又能表现出稳定的调温性能。

In order to study the influence of phase change material on low-temperature crack resistance and temperature regulation performance of warm mix asphalt mixtures,low-temperature splitting test,temperature stress tests of constrained specimen,nuclear magnetic resonance technology,differential scanning calorimetry were carried out,and the surface temperature of asphalt pavement layers on the test section was measured.The results show that phase change material can achieve heat absorption and release well in the process of rising and cooling.What’s more,it is found that its temperature regulation effect in the cooling process is more obvious by comparing enthalpy values.According to the field temperature measurement,the phase change asphalt pavement is about 6℃higher than that of the ordinary asphalt pavement,and the cooling start time is delayed about 60 min.However,with the increase of phase change material dosage,the splitting strength of phase change material asphalt mixture decreases,freeze-off temperature and turning point temperature rise,and the porosity increases,which reduce the low temperature crack resistance of asphalt mixture.The correlation analysis shows that the correlation coefficient of porosity with low temperature splitting strength,freezing break temperature and turning point temperature is above 0.97,and all indexes are closely correlated.Therefore,adding phase change material into asphalt mixture can effectively improve the temperature of asphalt pavement,but it will have a certain negative impact on the anti-crack performance of asphalt pavement.At the same time,the Logistic curve fitting of freeze-break temperature and turning point temperature shows that when the phase change material content is 3‰,the strength of asphalt mixture can not only meet the specification requirements,but also show stable temperature regulation performance.