ASPHALTopics | Fall 2020 | VOL 33 | NO 3

CONTRIBUTE TO SAFE,
QUALITY ASPHALT
ROADWAYS
Factsheets
by Doubra Ambaiowei
Safe and quality asphalt roadways, acquired through proper design
and construction and timely maintenance, remain a prime objective
for all stakeholders in the road building industry.
However, this pursuit can be challenged by low-bid contract
practices, limited budgets, increasing traffic volumes,
climate-change, use of substandard materials, proliferation
of specifications, and other factors. Industry-practitioners
recognize that these challenges must be addressed. They
require that we consistently strive for the best strategies that
can guarantee good quality roadways, fair value for the work
undertaken, and a healthy competitive market that enables
innovation.
The Ontario Asphalt Pavement Council (OAPC), through
its Quality of Asphalt Review, provided a framework of
recommendations on the best approaches to ensure longterm
value for safe and quality asphalt roadways. The Quality
of Asphalt Review was commissioned in the fall of 2017 and
completed in the summer of 2018. It was managed by KPMG and
included analysis conducted by the Texas A&M Transportation
Institute (TTI).
The framework focuses on ten relatively straightforward
technical facts to serve as reminders in the quest for durable
asphalt pavements. They include:
1. DO YOUR HOMEWORK
Evaluate existing pavement conditions meticulously
and perform proper pavement designs to determine the
appropriate thickness. Select the right mix and Performance
Graded Asphalt Cement (PGAC) for the project.
2. ENCOURAGE MIXES THAT HAVE HIGHER ASPHALT
CEMENT (AC) CONTENT
Studies have shown that mixes with higher AC outperform
those with lower AC content. Three approaches to get more
AC in HMA mixes are: the concept of gyrations depending on
the mix type and design traffic; the Superpave 5 concept which
uses a design air void content of 5 per cent instead of the
current requirement of 4 per cent; and, regressing air voids
as part of a balanced mix design.
3. SPECIFY A FINER GRADATION FOR YOUR MIX TYPE
Finer Superpave mixes typically have higher AC content
and are more durable and less prone to segregation.
4. DON’T OVERHEAT THE MIX
Overheating the mix will result in premature oxidation which
may lead to cracking. Specifying warm mix asphalt (WMA) may
help alleviate these concerns during late season paving.
5. INCLUDE ADEQUATE SURFACE PREPARATION IN THE PLANS
Contract documents should allow for suitable surface
preparation to ensure the construction of smooth roads.
6. ENSURE AN ADEQUATE BOND
Proper tack coat application ensures that the pavement will
perform as designed and help mitigate premature cracking.
Good tack coating will also improve compaction.
7. PROVIDE PROPER PAVEMENT DENSITY
Compacting the mat to the required specification limits will
ensure long-term durability, lower oxidation (due to long-term
aging), and reduce permeability.
This is a revised and updated version of the article that appeared
in Heavy Equipment Guide in March 2020.
24 OAPC | ASPHALTOPICS