Reprinted from Texas Construction July 2000
By Shanna Boats
Like many Texas cities, Bedford has initiated a recycling program. But in this case, the city has been recycling not just paper, glass and plastic, but some of its own streets. By adding cement to the existing road base, the city was able to reap surprising benefits and savings.
Most of the 455 lane miles that Bedford citizens travel each day were constructed between 1977 and 1986 with hot mix asphalt. Due to the age of the infrastructure and the city's explosive population growth, growing from approximately 5,000 in 1951 to more than 50,000 today - it became increasingly apparent that most of those streets were in need of reconstruction or some type of repair.
In response, the Bedford City Council developed the "4B Program," in 1997, an action based on Section 4B of the Economic Development Corporation Act of 1979. Voters approved a half-cent sales tax on Nov 4, 1997, allotting $16.3 million for street repair and reconstruction. The city then hired the architecture/engineering firm HNTB as its general consultant and design and construction services manager.
Of the entire project, 12.68 miles of asphalt streets were recycled in place by Sutton & Associates of Keller. The recycling method "is for streets that need more extensive work, but don't warrant complete reconstruction," explained J. C. Wood Jr., EE, director of public services for the city of Bedford.
Bedford used the North Central Texas Council of Government's Standard Specification to govern construction of the new base material. The existing material varies throughout the city, depending on whether the soil or base material is untreated, has an existing lime- or cement-treated subgrade or is a highly plastic clay. The streets being recycled in Bedford typically consisted of a combined total of six to 12 inches of lime-treated or cement-stabilized base material and asphalt. These were pulverized in place with high efficiency pulverizers.
After the grinding process, cement and water were added and mixed in. The-entire mixture was then compacted and cured. Austin Bridge and Road Inc. was subcontracted by Sutton & Associates to apply a 2-in. layer of hot-mix asphalt wearing course that, in many cases, was ready to drive on the following day.
Listing the benefits of the recycling method. Wood said, "It is so much faster...You gain almost as much life as if you had built a new street...You've increased the strength of the street by adding the cement." Because of their strong base, Wood expects the recycled streets to be rut resistant as well.
Recycling also saved money, Wood observed. "We spent $760,103 on the 12.68 miles we recycled, whereas we spent $5.8 million on 10.58 miles of new construction. So there is a considerable difference in cost."
James E Amick, EE, project manager of HNTB-Fort Worth, said, "It is very environmentally responsible because you don't waste any material or haul it off to a landfill somewhere. You reuse those resources that have been there on the street and that the city has already paid for. All you have to do is mix those good materials with cement and you have a new street for relatively little cost. As a consulting company, we have recommended this process to other cities with which we are involved."
This cement recycled asphalt base stabilization is a flexible base material as opposed to a true, strong concrete," Amick added. "We're projecting anywhere from 7-10 years before there will need to be some type of maintenance, like another overlay. In essence, we're trying to give the city streets that will last 20 to 30 years with proper maintenance."
During the concentrated effort to improve its city streets, Bedford also paved 23.8 lane miles with Portland cement concrete. While the recycling process was used for local and residential streets, concrete was used for Harwood Road, Central, Ravenswood and Murphy Drives.
The city of Bedford currently has its last street under contract, Wood said. "So, except for that one, we are pothole-free in the city of Bedford. We're pretty proud of that. We have nice-looking streets all over."
©2005 Road Recycling Council
P.O. Box 17362 - Cambridge, MA 02141
phone: (857) 998-0119 fax: (617) 547-0042
www.roadrecycling.org