The current binder testing protocols in the oscillatory domain use peak stress–strain data for material characterisation. The viscoelastic linearity limits are also based on such data. For a rigorous characterisation of the viscoelastic response of the binder, it is necessary that one records the complete waveform of the material response during oscillatory testing. This paper reports the waveform recorded for unmodified, crumb rubber modified and Styrelf modified bitumen during oscillatory loading. The waveform was collected for strain amplitudes of 1% and 5% at 30°C, 40°C and 50°C temperature. The linear and nonlinear behaviour of the material was studied using the geometrical symmetry of Lissajous plots. It was found that the material response was nonlinear. An appropriate frame invariant nonlinear constitutive model was used to predict the waveform response of all the binders tested.

Warm mix asphalt (WMA) technology is used to reduce mixing and compaction temperature of the binder; however, such addition is also expected to influence the rheological response of the binder during pavement service. This investigation is focused on WMA binders produced using Evotherm (Evotherm-VG30) and Sasobit (Sasobit-VG30) with a base binder (VG30). Shear rate sweep tests and steady shear tests conducted in the temperature range of 100–155°C indicate that the addition of Evotherm and Sasobit consistently reduce the viscosity of binder. This change in viscosity is found to be temperature and aging dependent. Short-term aged Evotherm-VG30 and Sasobit-VG30 binders exhibited increased shear thinning in the compaction temperature regime. Oscillatory shear tests and repeated creep and recovery tests were conducted in the temperature range of 15–75°C. The relationship between dynamic modulus and phase angle of WMA and VG30 binders followed Kramers-Kronig relations. Addition of Sasobit and Evotherm did not change the temperature regime associated with viscoelastic solid-fluid transition. From the creep and recovery test, addition of Evotherm and Sasobit resulted in increased strain during creep at higher temperatures. The influence of additives, especially Sasobit, on the base binder was found to be strongly temperature dependent.

In the current practice of flexible pavement design as per Indian Roads Congress (IRC), the influence of cyclic change in pavement temperature, traffic speed and aging on the material behaviour has not been considered. However, these factors influences the behavior of bituminous mixture and hence the pavement thickness. In this investigation, the influence of temperature, vehicle speed and aging on the dynamic modulus of the bituminous mixture was considered and an IRC pavement cross section was analyzed using AASHTOWARE pavement ME design software. The traffic data required for the design was collected from an existing National Highway and weather data used corresponds to Chennai city. For material characterization, two types of bituminous mixture sample were fabricated in the laboratory satisfying the Bituminous Concrete grade-2 (BC-2) and Dense Bituminous Macadam grade (DBM) specification of the Ministry of Road Transport and Highways, India. The dynamic modulus of these samples were measured at frequencies ranging from 0.01 to 25Hz at temperatures ranging from 5 to 55°C and the mater curve was constructed and used in the pavement design. It was found that most of the cross-sections failed to satisfy the design requirements when subjected to rigorous analysis, design and proof- checking. For a target life of 8 years, the required thickness of the bituminous layer was worked out and the thickness was found to be considerably high when compared to the existing thickness as proposed in the IRC guidelines