REAS may be applied with standard continuous flow slurry seal equipment or by hiring the services of a central mixing plant and its distributor trucks. Application with continuous flow equipment would be the same as applying traditional slurry seal, with an on-board mixer discharging the slurry mix into a screed for uniform application onto the pavement.
A central mix plant
Petrochem Marketing Inc. has set up a central REAS slurry mix plant in Los Angeles. From there, the company can dispatch the REAS mix in special trucks with a built-in agitator to keep the material mixed while it is being transported to the jobsite. A spreader box is attached to the rear of the truck so that the slurry mix can be deposited from the tank for spreading onto the pavement. A water tank and spray bar is also built onto the truck at the front end to dampen the pavement before applying REAS.
The advantage of this portable system is that it allows any size project to be slurry sealed, so the local agency can rent the necessary equipment and perform the application when desired. The local agency does not need to maintain a stockpile of aggregate near the project. The installation of more REAS slurry mix plants in California is planned.
The City of Los Angeles Bureau of Street Services (B.S.S.) utilizes the central mix REAS concept exclusively in their annual pavement slurry seal program. This fiscal year, July 1, 2004 through June 30, 2005, they will apply over 300 lane miles of centrally mixed REAS to their residential asphalt paved streets. The Bureau of Street Services with Petrochem has created a public/private partnership that improves street preservation through the use of pre-mixed REAS. Slurry seal projects that would take weeks to complete under the conventional method are now completed within eight hours. For every 100 miles of pavement surface slurry sealed with REAS, approximately 25,935 used tires are recycled.
This partnership provides a uniform consistent product that can be delivered on site by equipment that provides easier application and greater mobility. This innovative and effective premixed, rubberized product has economic and environmental advantages, while extending the life of valuable infrastructure.
The process and product is now a Bureau of Street Services preventive maintenance standard. The Bureau of Street Services and Petrochem Marketing Inc. were awarded the Federal Highway Administration (FHWA) 2003 Environmental Excellence Award as a result of the REAS work.
What is the life of REAS compared to traditional slurry seal? Joel Halbert, recently retired as materials engineer for the City of San Diego, has been involved with the use of this product on San Diego's streets. He states that the nearest source of crushed granite aggregate suitable for slurry seal was in the Riverside area, some 90 miles away. Before REAS, Halbert says San Diego had to reseal pavement after three or four years. But test strips of REAS placed about 4 ½ years ago in San Diego still retain the black seal coat, and it appears that the seal will last at least six years. Halbert states that the extended life of REAS over the long haul outweighs the fact that it costs approximately 15 percent more than traditional slurry seal. For that reason, the City of San Diego is spending $5 million per year for its Rubberized Emulsion Asphalt Slurry Program.
The 1998 Supplement of the "Standard Specifications for Public Works Construction" (Green Book) has added Section 600-3.2 Rubberized Emulsion Aggregate Slurry to the Specifications. The supplement can be purchased from Building News, 1612 South Clementine Street, Anaheim, CA 92802. The phone number is (714) 517-0970.
To summarize, REAS is a preventive maintenance product that provides many benefits, including the diversion of used tires from waste sites back to the streets. Another advantage is that the long-lasting, thinner, tighter, emulsion-rich, continuously black product creates a blacker surface. This provides a superior contrast with pavement markings, making them easier to see, which in turn leads to safer streets and highways for the motoring public. REAS is also more cost-effective as an asphalt pavement protection material than normal slurry seal. For all these reasons, we will probably see more rubber hitting the roads in the near future.