Linear viscoelastic response of emulsified-asphalt cold recycled mixtures

The current study investigates the linear viscoelastic response of emulsified-asphalt cold recycled mixtures (ECRM), incorporating reclaimed asphalt pavement (RAP), fresh aggregates, cement, water, and bituminous emulsion. Specifically, two types of ECRM are analyzed: a conventional mixture with 100% RAP (ECRM1) and a modified version with 75% RAP activated by heating (ECRM2). The research highlights the distinct mechanical response resulting from variations in production processes and the RAP content of the mixtures. The study examines the rate-dependent responses under various confinement conditions, temperatures, and frequencies through repeated haversine compression loading. Further, a novel approach to determine the reference temperature is proposed, and master curves are constructed using the generalized sigmoidal and Huet–Sayegh models. Even though ECRM1 and ECRM2 have different RAP content, production processes, and volumetric properties, the differences between the mixtures using the dynamic modulus and storage-modulus master curves are not substantial. However, the loss-modulus master curve distinctly captures the differences between the mixtures, with ECRM1 exhibiting a higher loss modulus due to its higher effective binder content. Moreover, the relaxation spectrum also captures the distinct response between the materials, mirroring the response seen in the loss modulus. It is also observed that confinement pressure significantly influences the dynamic modulus and storage modulus of ECRMs at low reduced frequencies. However, the influence of confinement pressure on the loss-modulus master curve and relaxation spectrum is negligible. This indicates that confinement pressure only influences the real part of the complex modulus, with no effect on the imaginary part.