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This paper presents a laboratory investigation into natural air convection and the establishment of intrinsic permeability of road and railway construction materials. The laboratory investigations were performed using a heat transfer cell with an inner volume of 1 [m.sup.3]. The study shows the importance of natural air convection and a practical method for establishing the intrinsic permeability of coarse granular materials. Three different open-graded crushed rock materials and two lightweight aggregates were tested. All materials were tested for downward (conduction only) and upward (convection and conduction) heat flow conditions. The experimental results revealed that all three crushed rock materials are prone to developing natural air convection in thermal gradients of 4.5 to 11 [degrees]C/m, depending on the particle size distribution. Foam glass aggregates showed a convective heat transfer flow at the fairly low temperature gradient of 6.5 [degrees]C/m. No natural air convection was achieved in expanded clay aggregates within the temperature gradients imposed. Intrinsic permeability values were established based on the experimental results. The intrinsic permeability of crushed rock materials ranged from 1.1 to 2.2 x [10.sup.-6] [m.sup.2] while that of foam glass materials was 0.9 x [10.sup.-6] [m.sup.2]. Key words: natural air convection, intrinsic permeability, road construction materials, crushed rock, lightweight aggregates. Cet article presente une etude en laboratoire sur la convection naturelle de l'air et l'etablissement de la permeabilite intrinseque des materiaux de construction routiere et ferroviaire. Les analyses de laboratoire ont ete effectuees a l'aide d'une cellule de transfert de chaleur d'un volume interieur de 1 [m.sup.3]. L'etude montre l'importance de la convection naturelle de l'air et une methode pratique pour etablir la permeabilite intrinseque des materiaux granulaires grossiers. Trois differents materiaux de pierre concassee a granulometrie ouverte et deux agregats legers ont ete testes. Tous les materiaux ont ete testes pour les conditions de flux thermique vers le bas (conduction seulement) et vers le haut (convection et conduction). Les resultats experimentaux ont revele que les trois materiaux de roche concassee sont susceptibles de developper une convection naturelle de l'air dans des gradients thermiques de 4,5 a 11 [degrees]C/m, selon la distribution granulometrique. Les agregats de verre mousse ont montre un flux convectif de transfert de chaleur a un gradient de temperature relativement faible de 6,5 [degrees]C/m. Aucune convection naturelle de l'air n'a ete obtenue dans les granulats d'argile expansee a l'interieur des gradients de temperature imposes. Les valeurs de permeabilite intrinseque ont ete etablies sur la base des resultats experimentaux. La permeabilite intrinseque des materiaux en pierre concassee variait de 1,1 a 2,2 x [10.sup.-6] [m.sup.2] tandis que celle des materiaux en verre cellulaire etait de 0,9 x [10.sup.-6] [m.sup.2]. [Traduit par la Redaction] Mots-cles : convection naturelle de l'air, permeabilite intrinseque, materiaux de construction routiere, pierre concassee, granulats legers., 1. Introduction Open-graded crushed rock materials are widely used in road construction in Norway, mainly due to their easy placement, absence of problems with separation and frost susceptibility, and very [...]

High-viscosity asphalt binder is a key material for porous asphalt pavement, but its susceptibility to aging limits its applications. Three recycled-based high-viscosity binders (RHBs), including RH-1, RH-2, and RH-3, were prepared by recycled rubber powder (RRP), recycled polyethylene (RPE), and waste vegetable oil (WVO), and compared with SINO TAFPACK-SUPER (SINO-TPS) high-viscosity asphalt (THA). The feasibility of recycling waste to prepare high-viscosity asphalt was verified by viscosity test, storage stability test, and thermogravimetric (TG) test. The rheological properties and aging resistance of binders were investigated by dynamic shear rheometer (DSR), bending beam rheometer (BBR), Fourier transform infrared (FTIR) spectrometer, and gel permeation chromatography (GPC). The results showed that the storage stability of RHBs is close to that of THA, and the viscosity is higher than that of THA but meets the specification requirements of high-viscosity asphalt binder. In addition, RRP/RPE can improve the high-temperature performance of the binder, and the addition of RRP/WVO can reduce the negative effect of low-temperature cracking of RPE. According to the changes of functional group index and binder molecular size in different aging states, ternary recycling waste can significantly improve the aging resistance of binders. The findings in this work contribute to reducing waste pollution and provides a method for high-viscosity asphalt binder production. [ABSTRACT FROM AUTHOR]

Crack healing has been a key area of asphalt pavement research. In this review, different crack-healing theories and crack-healing evaluation methods in bitumen and asphalt mixtures are summarized and presented. Then different crack healing technologies have highlighted the problems and solutions associated with their implementation. Detailly, traditional technologies (hot pouring and fog seal) are introduced. They mainly fill cracks from the outside, which can effectively prevent further damage to the asphalt pavement, when the cracks have generally developed to the middle and late stages of practical engineering. Their extension of the life of the asphalt pavement is relatively limited. Energy supply technologies (induction and microwave heating) have demonstrated significant efficacy in enhancing the crack healing capability of asphalt pavement, particularly in microcracks. Now, Extensive laboratory testing and some field test sections have been conducted and they are waiting for the promotion from the industry. The agents encapsulated technologies (Saturated porous aggregates encapsulate rejuvenators, Core-shell polymeric microcapsules, Ca-alginate capsule, Hollow fibers and Compartment fibers) not only heal cracks but rejuvenate the aged asphalt pavement. In order to promote industrial application, more field test sections and large industrial mixing and compaction equipment applications need to be implemented. Finally, some other potential crack healing techniques (coupling application, electrical conductivity, 3D printing, and modifications) are also mentioned. [ABSTRACT FROM AUTHOR]