Cold recycled asphalt mixtures (CRAMs) are generally comprised by reclaimed asphalt pavement, virgin aggregates, bitumen stabilising agents (asphalt emulsion or foamed asphalt) and active filler (Portland cement or hydrated lime). Depending on the type and content of each mixture constituent, the CRAM may exhibit different mechanical behaviours. The aim of this study is to evaluate the influence of mixture composition on the mechanical behaviour of CRAMs. The materials used were collected during the construction of an experimental test section and were used as base course mixtures. From triaxial resilient modulus test and dynamic modulus test, it was found that the type and content of bitumen stabilising agent and active filler substantially influence the behaviour of the CRAM. From triaxial resilient modulus tests, it was observed that the mixtures with cement addition behaved similarly to cementitious materials (independent of the confining pressure), while the ones with hydrated lime resembled a granular material (dependent of the stress-state). The dynamic modulus test results indicated that the CRAMs also exhibit viscoelastic properties. Besides, the test provided a clear difference between mixtures stabilised with either asphalt emulsion or foamed asphalt.

Phosphogypsum (PG) is a by-product of the phosphoric acid fertilizer industries that has possible applications in paving when stabilized with cement or lime. This study’s aim is to compare the mechanical performance of the hemi-hydrate (HH) and dihydrate (DH) mixes with tropical soil, lime, and cement. The results of physical, mechanical, and mineralogical tests are presented, which demonstrate that the use of HH in cement and lime mixes reduces the swelling of this material compared to the use of DH; in addition, HH provides better mechanical behavior. These findings indicate that DH has limited application in pavement construction, but when converted into HH and mixed with tropical soil or chemical stabilizers, its alternative uses are possible, and more content (approximately 90%) of this material can be used.

Cold recycled asphalt mixtures (CRAMs) have been widely used in pavement construction and rehabilitation of base courses. Some studies describe it as granular materials, without stiffness dependency regarding temperature or frequency variation, while other researches state that it resembles a viscoelastic material. This indicates that the CRAMs mechanical behaviour is not fully understood. In the present study, dynamic modulus tests were conducted with CRAMs samples and the master curves suggested a viscoelastic behaviour for this type of mixture. The dynamic modulus results were used as input data in 3D-Move Analysis software and the pavement structure was simulated at different temperature conditions based on temperature instrumentation data collected from the field. It was found that the temperature dependency of CRAMs’ stiffness influences pavement mechanical behaviour. Besides, the relative stiffness between CRAMs and AC layers plays a major role in pavement response for varying temperatures. Therefore, CRAM's viscoelastic properties cannot be neglected.

This study characterised two bio-binders (named Bio A and Bio B) derived from pine wood resins and designed for full replacement of asphalt binder. Bio A and Bio B were compared to a petroleum-based asphalt binder (AC 30/45). Elemental analysis, Fourier-Transform Infrared Spectroscopy, Gas Chromatography-Mass Spectrometry, Thermogravimetric analysis, and Linear Viscoelastic characterisation were applied to evaluate the materials studied. The susceptibility to aging was evaluated by comparing unaged and short-term aged samples of the three binders. Bio A showed a penetration grade of 29 (0.1 mm) and softening point of 55.2°C, while Bio B showed 21 (0.1 mm) and 57°C, respectively. AC 30/45 showed a penetration grade of 30 (0.1 mm) and softening point of 55°C. Bio B was found as more prone to aging than Bio A and AC30/45. This result might be related to the higher presence of saturated fatty acid methyl esters in Bio B.