United States Department of Transportation
i
Fatigue and fracture properties of aged binders in the context of reclaimed asphalt mixes.
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2014-08-01
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Abstract:Evidence in the literature indicates that the stiffness of the asphalt binder increases and ductility of the binder decreases
with oxidative aging. Typically for unmodified asphalt binders, increase in stiffness or decrease in ductility is regarded
as detrimental to the fatigue cracking or fracture resistance of the asphalt binder. However, fundamentally the stiffness
of the binder and its strength are two different attributes that may not necessarily be related to each other. There is very
little information in the literature that relates the fatigue cracking resistance or strength of the asphalt binder to the
extent of oxidative aging. This information is not only important to assess the durability and cracking life of asphalt
pavements but is also very important in the context of reclaimed asphalt pavements (RAP). The use of RAP not only
reduces the waste produced from milling and removing the asphalt pavement layers at the end of their service life, but
also reduces the amount of asphalt required for the construction of new roadways. In an effort to improve sustainable
practices associated with pavement constructions, state DOTs have been gradually increasing the allowable percentage
of RAP in new asphalt mixtures over the last two decades. However, the asphalt binder in RAP is highly oxidized and
is deemed to be susceptible to load related fatigue cracking. The focus of this study was to investigate the effect of
asphalt binder oxidation on its fracture properties and fatigue cracking performance. To this end, fatigue cracking
resistance of an asphalt binder was measured at different levels of aging using a standardized glass bead composite.
The glass bead composite simulates the stress state that asphalt binders experience in the field, while it excludes
aggregate-asphalt binder interactions. Furthermore, this research also investigated the effect of aging on fracture
properties of an asphalt binder by conducting monotonic fracture tests using a poker chip test geometry. The findings
from this study provide a better understanding of the effect of aging on the fracture and fatigue properties of asphaltic
materials.
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