Mass. GreenDOT Implementation Plan Includes Rubberized Asphalt
Following two years of research, collaboration and public dialogue, the Massachussetts Department of Transportation (MassDOT) launched the GreenDOT Implementation Plan in December 2012, establishing 15 broad sustainability goals to decrease resource use, minimize ecological impacts, and improve public health outcomes.
Each goal is supported by three to five tasks to be implemented over the next eight years. These tasks are then followed by specific indicators, which identify implementation time horizons and divisions responsible for implementation.
Rubberized asphalt will be used increasingly through 2015 to meet the goals related to improved life-cycle impacts.
MassDOT has successfully used rubberized asphalt as a thin rehabilitation surface since 2008. The 1.25-inch asphalt-rubber gap grade surfacing takes advantage of the highly modified binder’s ability to resist reflective cracking in a reduced thickness application.
The reduced thickness concept for mixes with asphalt rubber binder was originally developed by the California DOT (CALTRANS) in the mid 1990s. The reduced thickness design was later verified by the Federal Highway Administration Accelerated Loading Facility Pooled Fund Study at the Turner Fairbank Highway Research Center in McLean VA.
The heavy rubber loading in the binder of 16-22 percent by weight of the liquid provides millions of discreet rubber particles in the binder system in each ton of mix that simply do not crack. This technique utilizes the engineering properties of the tire rubber in particulate form to inhibit and slow the progression of reflective cracking, according to the Rubberized Asphalt Foundation (RAF).
The rocks in the mix do not crack and confine the crack to the binder in between the rocks. As a crack begins to move through the binder in an asphalt mix, the crack is continuously impeded by the rubber particles loaded into the binder system, and the crack must find another way to get around the rubber.
More innovations with rubberized asphalt are expected in Massachusetts this year as the DOT raises the bar for sustainability, cost effectiveness and quality in its materials for use in highway paving projects, the RAF said.
© Scrap Tire News, June 2013