Research Abstracts Online
January 2009 - March 2010
University of Minnesota Twin Cities
Institute of Technology
Department of Civil Engineering
PI: Mihai O. Marasteanu
The Representative Volume Element of Asphalt Concrete at Low Temperatures
The critical distress in asphalt pavements built in northern regions is low-temperature cracking. Transverse cracks develop in the pavement at almost regular intervals to relieve high stresses produced by drastic drops in temperature. The current method to evaluate the low-temperature properties of asphalt pavements is based on indirect tensile creep (constant load) tests performed on 50mm-thick and 150mm-diameter specimens. This test is expensive to perform and is not suitable for detection of aging effects on the mechanical properties of the material. Previous research performed at the University of Minnesota suggested the use of a simpler method based on creep test of thin beams (6.25 x 12.5 x 100 mm) in three-point bending. The thin beams are small enough to allow for detection of aging effects on the mechanical properties. The information provided by this test method combined with the rheological properties of the asphalt binders and the temperature dynamics can provide a better understanding of the deterioration process at the pavement surface.
The main difficulty in implementing this method into practice is the use of small size specimens that may not capture the overall behavior of the actual pavement. The volume of material tested may not be representative, especially when the asphalt mixtures contained aggregate sizes that are larger than the smallest dimension of the beam. This research addresses the problem of the representative volume element of asphalt mixtures at low temperatures with analysis and modeling of an extensive matrix of experiments. The experimental part of this research consists of bending and direct tension tests performed on specimens of three different sizes from 14 asphalt mixtures. Experimental results will be further analyzed by finite element method and micromechanics modeling based on theory of composite materials and n-point correlation functions.
Raul Velasquez, Graduate Student