AN INVESTIGATION OF THE PULL-OUT STRENGTH OF ASPHALT CONCRETE EXPOSED TO VARYING FREEZING AND THAWING CYCLES

Abstract

ostsurfacedroadsaremadeofflexiblepavementwhich requires a huge investment in terms ofinstallation and maintenance. One of the mostseriousproblemsisstripping,whichisthelossof adhesion between asphalt coating and aggregate in thebituminous mixture, caused by the existence of moisture.Stripping might result in different types of distress such ascreep, raveling, rutting, shoving, cracking and low stability.Hot mix asphalt (HMA) environmental damage (stripping)is a material compatibility problem. If the materials arecompatible, they will form strong and long-term bonds, sothe HMA will resist stripping. However, if the mix has poorbonding,its resistanceto strippingwill belower. Inthis case,the bonds should be enhanced or the material combinationsshould be adjusted to achieve satisfactory performance.Stripping is one of the most difficult conditions to identifybecause it can take numerous forms and it is influenced bydifferentvariables,someofwhicharerelatedtothematerialsforming the HMA (i.e. aggregate, asphalt cement and anti-stripping agents). Other variables are connected to theweather conditioning, compaction, air voids, testing method,handling and storage of additives. Moreover, stripping is arate process based on the viscosity/temperature dependencyof bituminous binders. Also, stripping occurs as a function ofthe surface tension between aggregate and bitumen.