沥青混合料低温临界开裂温度的确定

为了同时考虑沥青混合料在降温过程中温度应力的累积和松弛作用，确定临界开裂温度，对试件进行了线收缩系数试验，并利用间接拉伸试验确定其抗拉强度和蠕变柔量，由蠕变柔量和松弛模量的关系得到松弛模量的Prony系列表达式；由Boltzmann叠加原理，得到温度应力公式，计算出不同降温速率下产生的温度应力，根据低温抗拉强度曲线，确定出沥青混合料的临界开裂温度，并对结果予以验证。结果表明:该方法考虑了应力累积和松弛二者的综合作用，能够较好地反映沥青混合料的低温开裂特性，其计算结果与约束试件温度应力试验结果相近；该方法不仅适用于恒定降温速率，还适用于现场连续变速降温工况；随温度的降低或降温速率的增加沥青混合料内部温度应力累积速度加快，临界开裂温度随降温速率增加而升高。 

Determination of critical thermal cracking temperature of asphalt concrete

In order to consider both the thermal stress accumulation and relaxation effects of asphalt concrete (AC) during the process of temperature drop, and determine the critical cracking temperature, the low temperature shrinkage coefficient tests were conducted on AC specimens, and the tensile strength and creep compliance were determined from indirect tensile tests. The Prony series representation of relaxation modulus was obtained from the theoretical relationship. The thermal stress was computed according to the Boltzmann superposition principle. Thermal stresses induced at several of temperature drop rates were analyzed and the critical cracking temperatures (CCT) were determined based on the tensile strength curve. The calculation results were verified. The results show that this approach can take both the stress accumulation and relaxation into consideration, and better represent the low temperature cracking characteristic of AC. The calculation results are similar to that obtained from thermal stress restrained specimen test (TSRST). This approach can apply to both uniform temperatures drop and continuous drop in the field. The rate of thermal stress accumulation increases with decreasing temperature or increasing drop rate. The CCT increases with increasing drop rate.