Study on the conservation of bituminous mixes in high mountain roads and coastal zones

Abstract

The main objective of road conservation is to maintain the characteristics of the platform elements to ensure that vehicle mobility is carried out comfortably and safely. The orographic conditions of Spain, with a large length of high mountain roads and others at sea level; and winter weather events, with low temperatures, wind, water, ice, snow,…, which cause deposits of particles, filler, soils, small metals, or sea salt on the pavement surface, can be dangerous in the circulation of vehicles. One of the traditional methods for maintaining wheel-pavement adhesion is to apply flux products, mainly salt (sodium chloride, NaCl) and calcium chloride (Cl2Ca), solidly or humidified (salt brine). This chemical fluxes have the property of preventing the formation of ice as antifreeze, or facilitating their melting if it has already formed. This research studies the influence of salt in the surface layer of pavement made of hot mix asphalt with conventional binder. The effect of the salt is analyzed under three different conditions: immerse the specimens in salt water; add salt as aggregate in the manufacture of the mix; and submerging the natural aggregate in water with several amounts of salt, dry it and then manufactured the mixture with it. The mechanical parameters of the mixture have been analyzed in the laboratory: density, air voids, adhesion, indirect tensile strength and plastic deformation. To do this, Marshall test, Water Sensitivity Test (ITSR) and Wheel Tracking Test have been performed. The properties of hot mix asphalt do not decrease significantly when it is manufactured of salt added as aggregate, neither when it is submerged in salt water. The bituminous mixture offers negative results when it is manufactured with natural aggregate submerged in water with salt previously, because the adhesion between the aggregate and the binder is low.