Fundamental Properties of Asphalts and Modified Asphalts, III

SUBTASK 2-3. NANOTECHNOLOGY: AFM ANALYSIS OF ASPHALT THIN-FILM
MICROSTRUCTURE PHENOMENOLOGY
Task Manager: T. Pauli
Personal: W. Grimes, J. Miller, J. Beiswenger
Statement of Problem
Asphalt pavements are known to fail over time by a combination of different mechanisms. The
modes of failure of asphalt pavements that are commonly sited are embrittlement due primarily
to steric and oxidative aging, fatigue cracking due primarily to loading cycles and moisture
(traffic), rutting due primarily to densification and plastic flow, thermal cracking due primarily to
low temperature embrittlement, and formation of potholes due primarily to breakdown of the
sub-base structure. It is further contended in the pavement community that all of the
aforementioned modes of failure are some how influenced by environmental conditions like
seasonal temperature swings and the presence of water. Why do pavements constructed to the
same specifications and subjected to similar environmental conditions and traffic loading fail at
different rates by different failure modes when different materials (e.g., asphalts and aggregates
derived from different sources) are used to construct the pavement?
Approach
In this subtask we have asked the question why pavements constructed with asphalt derived from
different crude sources, if all other variables were to be kept the same, perform differently in
terms of moisture compounded fatigue resistance. For example, pavement cracking is often
observed to form distinct patterns during the lifespan of the pavement. In many other fields of
material science, metallurgy for example, pattern forming cracking has been successfully
correlated to the formation of microstructural grain boundaries which originate in these materials
during casting [Cappelli et al. 2008; Bian and Taheri 2008]. This same pattern cracking
phenomena can also be applied to paving materials [Robertson et al. 2005, 2006]. The approach
will be to develop quick and inexpensive experimental techniques derived from other fields of
materials nano-science. Results from these tests can then be combined with chemo-mechanical
models of asphalt-aggregate composite materials to predict pavement performance.
Goal
The goal of this work is to gain a more fundamental understanding of the composition of asphalt
concrete paving materials and how it relates to pavement performance (specifically fatigue
cracking/self healing compounded by the presence of moisture).
Support of FHWA Strategic Goals
This work plan supports the following FHWA focus areas. Pavement Design and Analysis: This
work will provide a more fundamental understanding of the physico-chemical nature of asphaltbinder
and chemo-mechanical properties of mastics as they relate to pavement performance.
Optimum Pavement Performance: A more fundamental understanding of the physico-chemical
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