An evaluation of the tensile strength of asphalt binder and mortar with recycled asphalt additives at low temperatures
Abstract
A standard grading system is used to evaluate the properties and expected
performance of an asphalt binder. The most common grading system used in the US today
is the performance grading (PG) system. This system prescribes an operational
temperature range within which the binder is expected to perform satisfactorily without
resulting in rutting, fatigue cracking or thermal cracking as a distress. On the low-temperature
and thermal cracking end, this system uses both a metric related to stiffness
and rate of relaxation (m-value) to establish a low temperature grade for a given asphalt
binder. Although these parameters provide some information on the rate of relaxation and
overall rigidity of the asphalt binder they don’t include an evaluation of the tensile strength
of the asphalt binder. The tensile strength of the binder can furnish critical information
about its resistance to cracking including thermal cracking. The asphalt industry has
become particularly interested in the impact of recycled asphalt pavement (RAP) and
additives such as rejuvenators on the behavior and performance of the material. The goal
of this study was to evaluate the tensile strength characteristics of asphalt binders and
composites in addition to their stiffness characteristics. The study was conducted in three
parts: (1) the evaluation of tensile strength of asphalt binders with similar performance
grades, (2) the evaluation of tensile strength of asphalt binders as a function of the amount
of recycled asphalt binder added to the virgin binder, and (3) the influence of recycled
asphalt and rejuvenators on the stiffness and tensile strength of asphalt mortars. In addition
to these three objectives, this study also developed simplified methods to prepare and
evaluate the tensile strength of asphalt binders and mortars as a material characterization
tool to screen or evaluate the efficacy of RAP, rejuvenators, and other additives. Results
show that similarly graded binders have a significant variability both in terms of their
stiffness and strength and that rejuvenators can be used with RAP to achieve a balance of
stiffness and strength.
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