Sodium chloride effect in the mechanical properties of the bituminous mixtures

The purpose of this research is the study on the influence of salt (sodium chloride, NaCl) in bituminous mixtures to know the variation in mechanical properties such as adhesiveness aggregate-binder, mechanical strength, ravelling and plastic deformations of mixtures. To do this, three types of mixture have been evaluated: a hot mix asphalt with conventional bitumen; and two porous mixtures, one manufactured with a conventional binder and another with modified binder. The effect of the salt is analysed for three different interactions: immerse the specimens in salt water; add salt as aggregate into the mixture; and submerge the aggregate in water with a certain concentration of salt, dry it and then make the mixture with it. The mechanical performance of the mixtures have been determined by Indirect Tensile Strength (ITS), Water Sensitivity Test (ITSR), Wheel Tracking Test and Cantabro Loss Particle Test. The results show that the hot mix asphalt is scarcely affected when it is submerged in salt water, neither when salt is added as aggregate. However, the porous mixture is more susceptible to the effect of salt for all salt interaction, especially when the aggregate has been submerged in salt water before making the bituminous mixture. The salt in the porous mixtures has a harmful effect, it causes a loss of internal friction.