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A laboratory investigation was performed to better understand the performance of Cement-Treated Base (CTB) mixtures containing Recycled Asphalt Pavement (RAP) during a long-lasting service period. Two CTB mixtures, one containing only virgin aggregates and the other containing RAP and virgin aggregates, were tested by triaxial tests (static and cyclic) and resonant column tests to evaluate stiffness and dampening at very small deformations. Similar mechanical properties and response to cyclic loadings were obtained for the two mixtures. The results led to the conclusion that the use of RAP as a replacement for virgin aggregates for a CTB mixture does not cause any significant alteration in terms of mechanical performance.

To promote asphalt self-healing, asphalt mixture can be heated via induction heating. This technique consists in adding electrically conductive and magnetically susceptible particles (e.g. steel) into asphalt mixture; then, with the help of an induction heating machine asphalt mixture can be heated. When the temperature of asphalt mixture is above a certain threshold (between 30 °C and 70 °C, depending on the type of bitumen), microcracks start self-healing. Induction healing has been previously demonstrated for repairing asphalt mixture test specimens broken in two pieces, but this technique has never been used for repairing microcracks caused by fatigue damage. In this article, the optimum moment and temperature needed to repair asphalt mixture under fatigue damage have been experimentally determined. With this purpose, Marshall test specimens have been damaged through indirect tensile fatigue tests and healed via induction heating. Finally, damage and healing have been quantified through computed tomography scan tests.

The nature of blending of virgin materials with reclaimed asphalt pavement (RAP) has been investigated using a multi scale approach using the dynamic shear rheometer (DSR), electron microscopy and computer tomography (CT). In order to simplify the visualization of the blending of the virgin and reclaimed materials five specially engineered hot asphalt mixtures were produced incorporating large mineral fraction (8/11 mm) of virgin aggregates and small fraction (2/4 mm) from RAP mixed with virgin bitumen. The complex modulus and phase angle of reclaimed binder from the blended mixtures were found to be between that of RAP and virgin binder. The CT slices of compacted cylindrical samples (150 mm diameter × 120 mm height) could incorporate the effect of compaction on the blending. They show lumped regions with virgin large aggregates as well as lumped regions of RAP aggregates. Using micro CT the spatial distribution of the different binders was investigated at the micro-scale. Millimeter size distinct clusters of virgin binder and clusters of RAP binder could be distinguished. The existence of RAP binder next to large virgin aggregates indicated the migration of the old RAP binder from the RAP aggregates to the virgin aggregates. From these CT images, it was not possible to verify if blending between the virgin and old binders occurred. Using electron microscopy micro-crack formations in the zone between old and new binder were identified suggesting weak spots that could lead to larger crack formation and propagation. However, using energy-dispersive X-ray spectroscopy good qualitative distribution of titanium dioxide tracer in the virgin binder in the mixture could be seen, indicating good blending at the investigated location. Hence, the results show that blending is not homogeneous throughout the sample. Some locations show good blending whereas other locations appear non-blended with micro-cracks forming at the binder boundaries.

Reclaimed Asphalt Pavement (RAP) recycling in pavement engineering can be actually carried out by means of hot recycling and cold recycling. An additional option arise from mixing with natural aggregates to build the sub-base layer. This paper shows the first results of a research activity undertaken on a test track specifically constructed with the aim to analyze the effect on pavement performance of a sub-base layer mixture with 50% of natural aggregates and 50% of RAP. The investigation is based on LWD and FWD analysis, comparing results with those obtained on the subsequent section of the test track made by only natural aggregates.

Using increased proportions of Reclaimed Asphalt Pavement (RAP) in asphalt pavements construction has become a top priority due to significant economic and environmental benefits. A similar trend has also emerged in Recycled Asphalt Shingles (RAS), which represent the main roofing material in US. In this paper, the effect of adding RAP and RAS on low temperature properties of asphalt mixtures is investigated using microstructural analysis and modeling of rheological data obtained on eight asphalt mixtures. Detailed information on internal microstructure of asphalt mixtures is obtained from digital images of asphalt mixtures beams and numerical estimations of spatial correlation functions. It is found that that microstructure spatial distribution is not affected by RAP and RAS addition. Mechanical analog (Sharpe, 2008 [18]) and semi empirical models are used to back-calculate binder creep stiffness from mixture experimental data. Differences between back-calculated results and experimental data suggest blending between new and old binder may be only partial.

This research has been dedicated to the experimental study of two different types of marls through uniaxial compressive tests on prismatic specimens. Induced deformations were measured during testing by classical extensometers and by means of photogrammetrical measurements. Either one or two cameras were employed to allow, respectively, 2D or 3D (using a stereoscopic vision) displacement measurements. A specific software was developed and applied to determine displacement and deformation maps at each photogram on the whole specimen surface. The interpretation of experimental tests, carried out for a better understanding of failure phase in weak rock before crack propagation starts, is illustrated in the paper.