ASPHALTopics | Spring 2020 | VOL 33 | NO 1

contents, the RAP asphalt binder properties. In some cases,
additional aggregate tests such as polishing or mineralogical
composition of the RAP aggregate may be necessary. The
testing data is not only necessary for use in mix designs, but
also essential for assessing uniformity of the RAP. Sampling
at 1,000 tonne intervals during processing from raw RAP into
a working stockpile is recommended. As with all materials,
consistent RAP is important to producing consistent mixes,
especially as RAP contents increase.
For quality control and quality assurance purposes, it
would be desirable to quantify the amount of RAP in a
recycled hot mixture. If RAP is incorporated in higher
amounts than approved without a proper design, it can
affect the integrity of the mix and can compromise the
performance and lifespan of the pavement.
The National Cooperative Highway Research Program
(NCHRP) Reports 452 and 752 provide a comprehensive
laboratory study to answer basic questions about preparing
and characterizing RAP materials for mix designs. The
National Asphalt Pavement Association (NAPA) Quality
Improvement Series 129 provides best practices and
guidance for management of RAP (from the time of
collection through processing, sampling and testing of
RAP for mix design) and quality control practices during
production of asphalt mixtures containing RAP. Readers
interested in a concise summary about the responsible
use of RAP are encouraged to consult OAPC’s (formerly
OHMPA) ABCs of RAP.
5. A total commitment is required from asphalt producers
to ensure that maximum allowable percentages of RAP
are not exceeded during production of the mix, and that
the governing industry mix design guidelines are being
adhered to. This is essential for developing and maintaining
a relationship of trust. OAPC continues to work with all
stakeholders to seek better ways of understanding asphalt
materials to produce durable asphalt pavements.
In summary, to use RAP responsibly, proper mix design
and ethical practices should be employed. This involves: 3
I. Determining the material properties of the RAP;
II. Selecting an appropriate blend of RAP and virgin
aggregate to meet gradation;
III. Selecting the appropriate PGAC for the
environment and traffic; and
IV. Designing a mix to comply with the applicable
contract and mix design requirements.
By using RAP responsibly, the specific benefits of recycling
such as reduced costs of construction, conservation of
aggregate and binders, preservation of the environment and
conservation of energy are achieved. All stakeholders in the
road building industry MUST make an effort at this to ensure
that our roadways meet their lifespan expectations.
38 OAPC | ASPHALTOPICS