Creep compliance of asphalt binders by indentation

Abstract

A solution for measuring creep compliance of asphalt binders is obtained by testing samples using a spherical indenter at intermediate temperatures. The initial assumptions considered a semi-infinite medium with no friction. Solutions were obtained to correct for the finite height and radius of the samples. Three non-modified asphalt binders were tested at intermediate temperatures (20 – 25 °C) using three load levels (25 – 50 – 75 g). Three sample radius (25 – 35 – 50 mm) and three sample heights (15 – 30 – 50 mm) were considered, thus obtaining a total of nine sample sizes. The binders were also tested in creep using a dynamic shear rheometer and results were compared with indentation. For the three asphalt binders analyzed, creep compliances obtained by indentation turned to be lower than the values measured using dynamic shear rheometers. One probable reason for this difference is the excessive aging that is induced on the surface of samples to be indented during sample preparation, as well as the effects of friction and indentation depth during testing. Future studies should consider the effect of friction in the indentation, which seem not to be totally negligible.