沥青胶结料低温临界开裂温度计算的改进方法

Improved method for calculating low temperature critical cracking temperature of asphalt binder

摘要:

针对当前沥青胶结料温度应力和低温临界开裂温度计算方法的局限性,为找寻一种更好的沥青胶结料温度应力及相应的低温临界开裂温度计算方法,选取4种不同产地的70^#基质沥青进行旋转薄膜老化（RTFO）和压力箱老化（PAV）展开研究. 利用BBR试验获得沥青胶结料的蠕变柔量,分别采用Hopkins & Hamming算法和CAM模型两步计算法以及Laplace变换一步计算法获得了沥青的温度应力,基于SAP理论计算相应的低温临界开裂温度. 通过统计学方法对计算结果进行比较和分析,采用相关性分析并结合实测路表温度数据对计算方法予以验证. 结果表明:Laplace变换一步计算法和Hopkins & Hamming算法两步计算法具有良好一致性,基于t检验法的低温临界开裂温度p值计算结果达0.90以上. Laplace变换一步计算法与BBR试验具有较强的相关性,临界开裂温度T_CR与S/m指标、Huet流变模型指标的相关系数分别可达0.84、0.94. 实测路表温度变化数据的计算结果证明了该方法不仅适用于匀速降温工况,也适用于任意降温速率下的现场连续变速降温工况.

Abstract:

In view of the limitations of the current calculation methods for thermal stress and low temperature critical cracking temperature of asphalt binder and in order to find a better method for calculating thermal stress and corresponding low temperature critical cracking temperature of asphalt binder, the 70^# matrix asphalt of four different origins was selected for rotating thin film oven (RTFO) and pressure aging vessel (PAV) tests. The creep compliance of the asphalt binder was obtained by BBR test. The thermal stress of the asphalt were obtained by two-step calculation method of Hopkins & Hamming algorithm and CAM model as well as one-step calculation method of Laplace transform respectively, and the corresponding low temperature critical cracking temperature was calculated based on SAP theory. Calculation results were compared and analyzed by statistical methods. The calculation methods were verified by correlation analysis and combined with measured road surface temperature data. Results show that the one-step calculation method of Laplace transform and the two-step calculation method of Hopkins & Hamming algorithm were in good agreement. The calculation result of p-value of low temperature critical cracking temperature based on t-test was more than 0.90. The Laplace transform one-step calculation method had a strong correlation with the BBR test. The correlation coefficients between the critical cracking temperature T_CR and the S/m index as well as the Huet rheological model index reached 0.84 and 0.94, respectively. The calculation results of the measured road surface temperature change data prove that the proposed method is not only suitable for uniform cooling conditions, but also for on-site continuous variable speed cooling conditions at any cooling rate.