Propriedades mecânicas de cimento asfáltico RTFOT e adicionados de PPA e LCC por microscopia de força atômica

Abstract

The rheological study of asphalt cement (AC) has an fundamental importance for its perfomance in manufacture of roads. The rheological parameters of this material are usually obtained by means of a dynamic shear rhometer. The present work aimds to study microreological properties of asphalt cement by force microscopy using an atomic force microscope (AFM). The atomic force microscope has shown to be a useful tool in investigation of mechanical properties of microcopic systems. The basic priciple of AFM is to measuare the micromechanical forces between the probe and the analyzed sample. It can be obtained not only topographic maps of the surface, but also information about the rheological properties of material, suck as: elasticity, viscosity and adhesion, among others, as well as observing regions which have different properties on the same sample. Samples of pure AC 50/, aged AC and added with 2% LCC and 1% PPA were analyzed. The data of force curves acquired with the AFM were used in a software developed by research grou of the Advanced Microcopy Laboratory (LMA), in the Departament of Physcs, Universidade Federal do Ceará, written in MATLAB. It was obtained the young's modulus, viscosity, adhesion force between the probe and the sample and the total work of adhesive forces. For each kind of sample were made three coverslips for measuments, and each coverlips were analyzed in three different regions of 50 x 50 μm. The indentation was performed in four different frequencies: 0,5 Hz, 1 Hz, 5 Hz and 28 Hz. Phase image, topographic and friction image have also been obtained for each kind of sample. Theanalysis of the AC by AFM has been shown to be a new tool. In addition to mechanical quantities, the microstructure of the AC is investigated. The images may help clarify the molecular structure of the AC and compared to the models used to describe such structures.