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Ageing phenomenon plays a key role on asphalt mixtures performance and durability, being susceptible to diverse designing factors that can be adjusted during both design and industrial manufacturing process. Thus, this paper focused on assessing the effect of main designing factors on the ageing rate of asphalt mixtures. It was evaluated the influence of type and quantity of bitumen, the dosage of filler and the impact of mineral skeleton on the ageing process of a gap-graded mixture, when ranging such parameters within acceptable values due to possible slight changes during manufacturing process. Results denoted that all factors presented a relevant impact on the range of change in material stiffness, deformation susceptibility and resistance to fatigue cracking due to ageing process. According to the results, the type of bitumen and filler content were seen as the most influential factors while the quantity of sand presenting lower levels of variation due to ageing, obtaining a more durable and resistant material when using a denser mineral skeleton. [ABSTRACT FROM AUTHOR]

This article studies the phenomenon of ageing in asphalt mixtures, considering the impact of temperature, time and pressure via laboratory techniques, compared with roadway samples. In particular, the ageing of two mixtures was analysed, manufactured with a high voids content and with two different modified binders (SBS polymer and crumb rubber), while comparing results with those obtained for cores from a highway using similar mixtures in surface layer. The stiffness and fatigue cracking life of the mixtures were assessed, after different ageing periods at diverse temperature and pressure levels. Results demonstrated that the laboratory ageing simulation of asphalt mixtures strongly depended on the studied parameters. Long ageing periods (in this study 9 days) at a high temperature (135°C for the cases analysed in this paper) was required in order to reproduce a marked ageing impact, while providing the ability to differentiate the susceptibility of ageing of different materials. [ABSTRACT FROM AUTHOR]

A new generation of asphalt binders with mecanomutable properties has been developed, with the aim of obtaining smart materials able to adapt their mechanical performance to the real changing load conditions that occur during their service life. These materials are composed of a bituminous matrix that has been modified with magnetic particles that are able to change the mechanical behavior of the binder when they are activated by a magnetic field. This study examines the main variables that govern the mechanical behavior of these materials. The mechanomutable performance of different binders has been demonstrated under various concentrations of magnetic particles. In particular, these binders could increase their stiffness and perform elastically when they are activated by a magnetic field (even at high temperatures), which, once removed, enables the initial properties of the binders to be recovered. The changes induced in the properties of the binder depend on the amount of magnetic particles, the intensity of the magnetic field, and the type of bituminous matrix. The findings open up the possibility of a wide field of applications for its implementation in smart infrastructures, with special interest in the construction, rehabilitation, and maintenance of asphalt pavements. [ABSTRACT FROM AUTHOR]