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

Abstract

The road conservation activities allow 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, thermal gradients, 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). These 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 on the surface of a bituminous pavement. The interaction of salt and bituminous layer materials has been analyzed in different ways: first, the bituminous mixture is immersed in salt water; second, salt is another aggregate of the bituminous mixture; and finally, the hot mix asphalt is made with aggregate impregnated with salt in its surface. The properties of the mixtures have been analyzed in the laboratory: density, air voids, adhesion, indirect tensile strength and plastic deformation. To do this, Marshall test, Indirect Tensile Strength Ratio (ITSR), and rutting test have been performed. The properties of hot mix asphalt do not decrease significantly when it is manufactured of salt added as aggregate. It also offers good results when the specimens are inside recipients with 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 materials is low.