http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Investigation of the microstructural mechanism of relaxation in asphalt
Asphalt has a principal role in the strength of asphalt concrete; it holds the aggregates together in the matrix against the traffic loads and the widely varying environmental forces. The study of the physical properties of the asphalt provides the key information on the overall behavior of the asphalt concrete. The relaxation strength of an asphalt is a measure of its load carrying potential under the sustained state of deformation. The study of the relaxation strength of an asphalt would allow one to understand its creep behavior that causes permanent deformation in the asphalt concrete pavement. The relaxation strength of a material essentially depends on its molecular structure. Infrared (IR) spectroscopy is widely used to examine the molecular structure of the polymeric materials; it can offer information on the molecular changes occurring in the stretched state of the asphalt sample. A suitable deformation device was developed to deform the asphalt in the IR spectrometer sample chamber. The analysis of the IR absorption of the stretched asphalt indicated that the methylene chains were most active in resisting the mechanical stress on the asphalt. The peak ratio of the methylene (721 cm^-1) and methyl (1376 cm^-1) absorbance bands determined the representative length of the methylene chains in the asphalts. Dynamic mechanical tests on the rheometrics mechanical spectrometer (RMS) were used to examine the relaxation strength of the asphalts. The study showed the dependence of the relaxation strength of the asphalts on their representative methylene chain length.