The working temperature of a bituminous pavement can typically range from 75${}^{\circ }$C to $-{20}^{\circ }$C. Bitumen shows a wide spectrum of mechanical behaviour in this temperature range and these include those of a viscoelastic fluid, a viscoelastic solid and an elastic solid. Due to the amorphous nature of the material, the transitions between such mechanical responses are gradual. This investigation focuses on the transition between the viscoelastic solid and the viscoelastic fluid state of a wide class of bitumens with regard to unaged and short-term aged conditions. An unmodified binder and three modified binders were subjected to temperature sweep and frequency sweep in the viscoelastic regime across a wide range of temperatures. Depending on the material and the post-processing method followed, one could discern a viscoelastic fluid and a viscoelastic solid regime and a frequency-dependent mixture regime consisting of a viscoelastic solid and a viscoelastic fluid, across the tested temperatures and frequencies. It is shown in this investigation that parameters such as G${}^{\mathrm{\prime }}$–G${}^{\mathrm{\prime \prime }}$ crossover and frequency independence of tan δ cannot be used to estimate the temperatures corresponding to the onset of either fluid-like or solid-like behaviour of the body as the temperature varies. It is also shown that the time–temperature superposition principle does not hold good in the temperature regime tested (75–25${}^{\circ }$C) due to the viscoelastic transitions exhibited by bitumen and modified bitumen.

沥青路面的工作温度范围通常为75${}^{\circ }$到 $-{20}^{\circ }$C.沥青在此温度范围内表现出广泛的机械性能，其中包括粘弹性流体，粘弹性固体和弹性固体。由于材料的非晶性，这种机械响应之间的过渡是逐渐的。这项研究的重点是针对未老化和短期老化条件的各种沥青的粘弹性固体和粘弹性流体状态之间的过渡。未改性的粘结剂和三种改性的粘结剂在很宽的温度范围内在粘弹性状态下经受温度扫描和频率扫描。根据材料和后续的后处理方法，在测试的温度和频率范围内，可以分辨出粘弹性流体和粘弹性固体状态以及由粘弹性固体和粘弹性流体组成的频率相关混合状态。该调查表明，诸如G之类的参数${}^{\mathrm{\prime }}$-G${}^{\mathrm{\prime }}$tanδ的交叉和频率独立δ不能用于估计对应于开始时的温度或者流体状或固体状随着温度改变的身体行为。还表明，时间-温度叠加原理在测试的温度范围内效果不佳（75–25${}^{\circ }$C）由于沥青和改性沥青表现出的粘弹性转变。