基于不同温度SCB试验的沥青混合料低温抗裂性能评价

Evaluation on Low Temperature Cracking Resistance of Asphalt Mixture Based on SCB Test at Different Temperatures

为更方便、准确地评价沥青混合料低温抗裂性能,通过对半圆弯曲(SCB)试验对断裂能成分进行分析,探究了断裂能随温度升高而增加的原因,提出了基于SCB试验计算沥青混合料黏性耗散能方法,并用于评价沥青混合料低温抗裂性能。通过设计SCB试验,测试并评价了6种沥青混合料低温抗裂性能。结果表明:沥青混合料断裂能随测试温度升高而增加主要归因于黏性耗散能的增加,通过SCB试验预估沥青混合料黏性耗散能,用以评价沥青混合料低温抗裂性能;以黏性耗散能作为低温抗裂性能评价指标,对比不同再生沥青混合料的黏性耗散能的变化幅度,可以发现最大变化幅度(AC20R40与AC20R40RA试验组的差异)达到72.2%,远大于断裂能的变化幅度,可有效区分不同再生沥青混合料的低温抗裂性能,同时也有利于降低试验误差对评价结果的影响;随着试验温度升高,沥青混合料从脆性破坏逐渐转为延性破坏,断裂面中集料断裂面积逐渐减少,且材料原子或分子振动更剧烈,造成沥青混合料表面能逐渐减小,所以出现断裂能随温度先增大后减小的变化规律,其由黏性耗散能引起,断裂能峰值点温度即为黏性耗散能峰值点温度;建议黏性耗散能以―12℃与0℃温度下SCB试验的断裂能之差进行计算,用以评价沥青混合料低温抗裂性能。

In order to enhance the convenience and precision of evaluating the low temperature cracking resistance of asphalt mixtures,an investigation into the rationale behind the increase in fracture energy with rising temperature is undertaken through an analysis of the fracture energy components of the SCB test.A method for computing the viscous dissipative energy of asphalt mixture based on the SCB test is proposed and employed for the assessment of the low temperature cracking resistance of asphalt mixtures.The low temperature cracking resistance of 6 asphalt mixtures is examined and appraised through the design of SCB tests.The result shows that(1)The escalation of fracture energy in the asphalt mixture with increasing test temperature is primarily attributable to the rise in viscous dissipation energy.(2)The SCB test is utilized to estimate the viscous dissipation energy of the asphalt mixture for the evaluation of low temperature cracking resistance.By utilizing the viscous dissipative energy as the assessment indicator for low temperature cracking resistance and comparing the change amplitude of the viscous dissipative energy of different recycled asphalt mixtures.It is observed that the maximum change amplitude(the difference between AC20R40 and AC20R40RA test groups)reaches 72.2%,which significantly surpassing the change amplitude of the fracture energy.This approach effectively distinguishes the low temperature cracking resistance of different reclaimed asphalt mixtures and mitigates the influence of test errors on evaluation results.(3)With the increase of test temperature,the asphalt mixture transitions gradually from brittle failure to ductile failure,leading to a reduction in the aggregate fracture area on the fracture surface and increased molecular agitation,resulting in a gradual decrease in the surface energy of the asphalt mixture.Consequently,the observed pattern of fracture energy increasing initially and then decreasing with temperature is attributed to the influence of viscous dissipation energy.The temperature corresponding to the peak point of fracture energy aligns with the temperature at the peak point of viscous dissipation energy.(4)It is recommended that the viscosity dissipation energy is calculated based on the difference in fracture energy from SCB tests conducted at -12℃and 0℃ to evaluate the low temperature cracking resistance of asphalt mixtures.