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Warm Mix Asphalt – A Greener Alternative to Hot Mix Asphalt


The Ministry of Transportation of Ontario’s (MTO) priorities include improving Ontario’s
highway infrastructure and integrating the principle of sustainability into ministry programs,
policies, and operations. The commitment to protect and preserve the environment and
encourage the sustainable use of resources on all projects is reflected in the mandate of the MTO
Provincial Highways Management (PHM) division “to deliver a provincial highway network that
is safe, provides mobility for people and goods, and promotes economic, environmental and
social sustainability.” MTO has a strong history of research, development, and implementation
of innovative green pavement technologies. One recent initiative that has been successfully
implemented is the use of Warm Mix Asphalt (WMA) on MTO construction projects.
Warm Mix Asphalt is defined as a group of technologies that allow for a reduction in the
temperatures at which asphalt mixes are produced and placed relative to traditional Hot Mix
Asphalt (HMA). WMA is produced and placed at temperatures 20º to 50º C less than
conventional HMA. The production and paving of asphalt at these reduced temperatures
generates fewer emissions and requires less energy while maintaining or enhancing pavement
MTO began preliminary research on the application of WMA to Ontario roads in 2006, followed
by initial WMA trial contracts in 2008. Between 2008 and 2009, MTO placed a total of 7,000
tonnes of WMA on five MTO contracts. Expanding upon its initial success, MTO constructed 10
WMA contracts in the year 2010, placing a total of 63,000 tonnes of WMA. To evaluate the
environmental benefits of WMA, MTO required additional tests and measurements be performed
on several of the 2010 contracts. These included emissions measurements at both the asphalt
manufacturing plant and paving site, temperature measurements of the WMA during production
and paving, and additional tests to assess WMA pavement performance (see Figure 1). In these
trial contracts, WMA paving occurred at temperatures 10º to 30º lower than conventional HMA
without any adverse effects on asphalt properties (see Figure 2). The WMA trials were
successful and supported increased WMA usage. As a result, MTO decided to target 10% WMA
use on contracts completed in 2011. In addition, MTO decided to include larger tonnages of
WMA than in previous years, and to use WMA in both the binder course and surface course

Conference Paper Details

Session title:
2012 TAC Environmental Achievement Award
Politano, L.
Environmental issues, Environmental legislation