Must be done well: The right mix design makes high RAP/RAS possible

Due to rising costs of building asphalt pavements, the asphalt industry must find ways to maintain the quality of asphalt mixes while stretching road-building dollars. The use of recycled materials - both reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) - is one such way. In order to reduce costs, RAP and RAS are being increasingly used in asphalt mixes to replace aggregate materials and virgin asphalt. The state of Texas used over 1 million tons of RAP and 150,000 tons of RAS in asphalt mixes in 2014, largely in hot-mix asphalt. Due to the nature of the recycled materials, however, they may result in a stiffer mix with a lower resistance to cracking. This necessitates a mix design method to systematically address this issue, as delineated here.