Fatigue cracking is one of the key distress types, caused by traffic load repetition generating stresses and strains in asphalt layers. In response, polymer modified asphalt (PMA) has been widely used in the field of pavement engineering and the addition of polymers to asphalt has been shown to improve mechanical behaviour and pavement performance, including fatigue resistance. However, it is uncertain to what extent standard fatigue tests measure this benefit. In this study, a Beam Wheel Tracker Fatigue Test (BWTFT) was developed to investigate the fatigue behaviour of both polymer modified and unmodified asphalt mixtures. The results showed that the BWTFT worked well and appeared to simulate road pavement cracking fairly realistically. Visible cracking began to appear at 50-95% of the time to full-depth crack development, later at lower temperature. A practical calculation is presented to estimate material modulus during the test and this shows a significant reduction throughout, with differing patterns for different materials and temperatures. Early stiffness reduction is deduced to relate to the development of micro-cracking. The differences between conventional and PMA performance are highlighted.

疲劳开裂是主要的破坏类型之一，由交通荷载重复在沥青层中产生应力和应变引起。作为回应，聚合物改性沥青 (PMA) 已广泛应用于路面工程领域，并且已证明在沥青中添加聚合物可改善机械性能和路面性能，包括抗疲劳性。然而，尚不确定标准疲劳测试在多大程度上衡量了这种好处。在这项研究中，开发了梁式车轮跟踪器疲劳测试 (BWTFT) 来研究聚合物改性和未改性沥青混合料的疲劳行为。结果表明，BWTFT 运行良好，似乎相当逼真地模拟了路面开裂。可见裂纹在 50-95% 的时间内开始出现，直至裂纹全深发展，稍后在较低温度下。提出了一个实际计算来估计测试期间的材料模量，这表明整个过程显着降低，不同材料和温度的模式不同。推断早期刚度降低与微裂纹的发展有关。突出显示了传统性能和 PMA 性能之间的差异。