|approved||ramm_summary_osi_11-1.pdf||2015-04-08 10:55:48||Adam Ramm|
Author: Adam S Ramm
Requested Type: Oral
Submitted: 2015-03-26 10:24:35
Co-authors: Sakib Nazmus, Amit Bhasin, M.C.Downer
University of Texas
Austin, Texas 78712
Asphalt binders used in construction of pavements must be chemically engineered to withstand wide climatic variations. Ideal binders possess high stiffness at high temperatures, low stiffness with high relaxation rates at low temperatures, and high resistance to fatigue cracking at intermediate temperatures. Such bulk properties are conventionally measured with rheometers, but appear to be closely connected with temperature-dependent microstructural changes such as cracking, rutting, and phase separation. AFM has been used to observe such microstructures, but is only practical near room temperature . Here we characterize asphalt binder microstructure over a wide range of temperatures and chemical compositions using noninvasive optical microscopy correlated with linear optical scatter to measure statistical fluctuations. For example, micron-sized “bee”-shaped structures previously observed by AFM  are resolved optically, and observed to vary in size, morphology and density as temperature and composition change, while inducing corresponding changes in optical scatter. We will present these and other optical measurements, and discuss their connection to bulk material properties.
 Pauli et al., Internat. J. Pavement Engin. 12, 291 (2011).