Multi-scale Modification to Enhance the Durability and Sustainability of DOT Asphalt Pavements
Focus Area
Waste Management/Recycling/Brownfields
Subcommittee
Environmental Process, Natural Resources
Status
Archived
Cost
$250k-$499k
Timeframe
2-3 years
Research Idea Scope
This research project will evaluate the feasibility,
cost-effectiveness and benefits of using multi-scale modified asphalt binder
and locally available low-cost materials and waste materials (e.g., recycled
plastics, reclaimed asphalt pavement – RAP, and fly ashes) in a synergistic
manner, so as to extend the service life of DOT AC pavements and achieving
balanced performance goals. This technology takes the advantage of technical
breakthroughs found in the recent advances in the nano-/micro- modification of
AC mixtures and in RAP and WMA technologies. The study will be conducted
according to the latest test specifications and protocols.
Recent research at the Western Transportation Institute
and elsewhere has demonstrated the clear benefits of nano- and
micro-modification of asphalt binders in enhancing the mechanical and
durability properties of asphalt concrete (AC). For instance, the addition of
nanoclay and/or carbon microfiber (both at less than 2% by weight of asphalt
binder) was shown to greatly enhance the tensile strength and fracture energy of
AC mixtures (as shown in the figures below) and remarkably reduce their
moisture susceptibility and risk of fatigue cracking. The benefits in
performance were especially significant when the AC mixtures were conditioned
in water or chloride-based deicer solutions. The multi-scale modification also
improved the rutting resistance of AC mixtures.
While a phased approach may be taken, the proposed
activities can be divided into the following parts: (1) Synthesizing DOT
multi-scale modified asphalt binders, based on the survey of current practices,
DOT user requirements (e.g., minimum pavement temperatures for the different
climatic zones), and materials availability and cost. The multi-scale modified
binders will be tested for constructability and only those with acceptable
constructability will be selected for further testing by the Bending Beam
Rheometer (BBR). Ideally three binders that show promise in greatly improving
AC properties will be selected for further investigation and their performance
grade (PG) will be evaluated according to Superpave criteria (AASHTO M320).
Additional testing may include: direct tension test (DTT) and the BBR at two
temperatures (AASHTO MP-1A) for a more in-depth analysis of low temperature
property. (2) Synthesizing DOT “green” AC mixtures using the identified binders
and low-cost materials available in . For the testing of mixture properties,
local aggregates will be used. Tests on coefficient of thermal expansion and
contraction, creep compliance, and indirect tensile strength will be conducted
for all AC mixtures under low temperatures. Depending on funding availability,
the mixtures may be further evaluated for their moisture susceptibility (AASHTO
T283) and Dynamic Modulus (AASHTO TP 62-03). Finally, this study will assess
cost-effectiveness and benefits of the best-performing unconventional AC
mixtures for highway construction by DOT.
Urgency and Payoff
This research is urgently needed in light of the
increased emphasis on the durability and sustainability of transportation
infrastructure. Environmental benefits can be achieved through the use of waste
materials and potentially lower construction temperatures as well as reduced
energy-consumption and footprint associated with the reduced need for pavement
repair/rehabilitation. The research findings will produce significant saving to
the State and Federal highway construction and maintenance budgets as well as
user costs in delays and accidents.
The use of multi-scale modification of asphalt binders
could provide a cost-effective approach to enhancing the durability and
sustainability of DOT AC pavements. From the durability perspective, low
temperature cracking is one of the prevalent distresses found in AC pavements,
reducing their performance and service life and leading to significant costs in
the preventative maintenance and repair of roads. While the FHWA LTPPBIND
software may recommend using a certain PG binder to fit the cold climate, such
binder would entail substantial cost and likely sacrifice pavement performance
at summer temperatures (e.g., rutting resistance). From the sustainability
perspective, warm mix asphalt (WMA) is a collective term that describes a range
of technologies employed to reduce viscosity of asphalt mixtures and thus make
it possible to place and compact AC mixtures at temperatures 30o to 100oF lower
than that of typical hot mix asphalt (HMA). Reduced viscosity by the use of WMA
technologies could bring several cost, environmental, and construction
benefits, yet there are concerns over long-term performance.
While there have been increasing usage of
nano-/micro-sized materials, recycled materials and WMA in AC pavements and a
growing body of positive evidence or user experience, a study to leverage
the recent advances and focus on the specific
DOT constraints and needs is much needed and timely.
Submitted
10/08/2013