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Resperion's IntegraBase asphalt
modifier makes it possible to improve lower-performing
performance-graded asphalt binders to the point where
they can meet stringent PG specifications for Superpave
mixes. Not only can IntegraBase improve the PG specifications,
but it also improves the resilient modulus and fatigue
resistance of the asphalt, further improving rut resistance
and flexibility for base and binder courses.
Historical
Asphalt Grading
Asphalt cements have historically been graded by two
empirical tests; penetration and viscosity. These
tests were developed over time using experiences with
asphalt pavements. These tests attempt to repeat past
successes, and avoid past failures. Empirical tests
work as long as all of the conditions at the time
of the test development remain unchanged.
Unfortunately, this is not true
of our asphalt pavements today. Penetration and viscosity
tests were developed in an era of less traffic and
significantly lower pavement loadings. Trucks of yesteryear
were limited to 72,000 lb. and rode on bias ply tires
with tire pressures of 75 psi. Today, truck weights
exceed 80,000 lb and radial tires are inflated to
125 psi. A 10% increase in truck weight results in
a 40% increase in stresses applied to the pavement.
These factors, along with the numbers of heavy trucks
traveling roads across the globe, subject asphalt
pavements to stresses, which result in rutting and
premature failure.
Superpave
Performance Grading (PG) System
The Superpave PG system was developed as part of the
Superpave research effort to more accurately and fully
characterize asphalt binders for use in HMA pavements.
The PG system is based on the idea that an HMA asphalt
binder's properties should be related to the conditions
under which it is used. For asphalt binders, this
involves expected climatic conditions as well as aging
considerations. Therefore, the PG system uses a common
battery of tests (as the older penetration and viscosity
grading systems do) but specifies that a particular
asphalt binder must pass these tests at specific temperatures
that are dependant upon the specific climatic conditions
in the area of intended use.
Superpave performance grading is
reported using two numbers - the first being the average
seven-day maximum pavement temperature (in °C)
and the second being the minimum pavement design temperature
likely to be experienced (in °C). Thus, a PG 58-22
is intended for use where the average seven-day maximum
pavement temperature is 58°C and the expected
minimum pavement temperature is -22°C. Notice
that these numbers are pavement temperatures and not
air temperatures.
The
IntegraBase Effect
It is the aim of every asphalt formulator to be able
to take the most economic source of asphalt and enhance
the high temperature properties and comply with low
temperature requirements in fulfilling PG targets.
IntegraBase makes the achievement of this objective
a reality while providing for additional technical
benefits at a minimal cost.
The following table illustrates
that blending IntegraBase with asphalt binder can
result in a two to three grade improvement in the
upper and lower temperature performance, although
these results may vary based on the properties of
the asphalt binder used. The unmodified asphalt binder
used in this test was an Egyptian 60/70 pen:
IntegraBase also provides for a
large increase in Resilient Modulus and fatigue life
- in most cases, IntegraBase will improve the Resilient
Modulus by 100% and the fatigue life by 50%. With
this additional pavement strength generated through
the use of the IntegraBase modifier, it is possible
to reduce the maximum strains which develop in the
pavement due to wheel-loads. This translates into
a superior-performing pavement that will be resistant
to both pavement deformation and pavement cracking.
Additionally, the improved pavement
strength and elasticity will increase the number of
standard axle loads which can be carried by the IntegraBase
modified pavement throughout its useful lifetime;
this can result in substantial life-cycle savings
in terms of pavement longevity and decreased maintenance.
Polymer Modified
PG vs. IntegraBase Modified PG
Polymer modification, which is a commonly used system
to change the properties of asphalt binders, can increase
the cost of the binder anywhere from 30% to over 100%.
This increase can make a significant impact on the
cost of the hot mix asphalt (HMA,) typically raising
the price 25% to over 50%. Because of the large increase
in cost, the use of Polymer Modified asphalt is limited
to use as a wear course modifier in high stress or
extreme climate applications. The use of Polymers
in base/binder applications wouldn't be cost effective,
nor could it match the benefits of IntegraBase from
Resperion. The following table summarizes up how Polymer
Modified PG compares to IntegraBase modified PG:
Not only is IntegraBase cost effective,
increasing the cost of a typical mix by less than
10%, rational pavement design techniques confirm that
base and binder course layers constructed with IntegraBase
can be reduced in thickness by up to 40%, while achieving
an equal or greater number of equivalent standard
axle loads (ESAL's) as conventional materials. Since
the cost of the materials saved exceeds the cost of
the MMC by a wide margin, Resperion enables you to
build the same road for less money.
About IntegraBase
Resperion's IntegraBase is a multi-metallic catalyst
(MMC) in asphalt soluble form. When mixed with asphalt
cement and aggregates, this catalyst initiates a series
of chemical reactions which ultimately cross link
the asphalt molecules and consume the catalyst; this
reaction creates an Organic Metallic Complex, the
strongest bond in all of Chemistry. The new higher-molecular-weight
materials created are extremely resistant to heat
and heavy loads. They also exhibit superior water
resistance and anti-stripping properties. Hence, when
using the Resperion modifier, other common additives
such as rubber, lime and anti-stripping agents may
not be required as the benefits of those additives
have already been provided. IntegraBase has been specifically
formulated to ensure that all of the increase in performance
properties is achieved by the time the road surface
is ready for use.
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