"Glasphalt" May Pave The Way For Worldwide Aviation In The 21st Century

For the first time, "glasphalt," which paved the way for recycling wasteglass into roads and parking lots, is being used to pave an airport runway,parking apron and taxiway. The project, at a general aviation airport inRolla, Mo., was completed in November 1996. One year later, the material isholding up exceptionally well, says Dr. Delbert E. Day, Curators' Professorof ceramic engineering at UMR and one of the inventors of glasphalt.

Ozark Rivers Environmental Inc., a not-for-profit corporation, used a grantfrom the Missouri Environmental Improvement and Energy Resources Authorityto demonstrate how waste glass can be easily and economically substitutedfor some of the rock and sand used in ordinary asphalt paving, and inpaints used to mark airport runways and taxiways.

"The purpose of the demonstration project is to show how some of the approximately 10 million tons of waste glass in the U.S. that cannotpresently be recycled into new glass products can be disposed of in alow-cost and beneficial way that avoids the costly disposal fees now beingpaid to put waste glass in landfills," Day says.

Three faculty members from UMR provided technical help in paving therunway, taxiway and parking apron at the Rolla Downtown Airport, a smallgeneral aviation airport.

After paving the 3,000-foot-long runway with four inches of glasphalt thatcontained 10 percent broken glass, it was painted with a paint that alsocontained waste glass as part of the pigment.

According to Day, about 450 tons of waste glass, crushed to 1/4-inch andsmaller, that would otherwise have been buried in landfills, was used inplace of some of the rock and sand in the glasphalt paving material.

"One of the advantages of glasphalt is that no special equipment is needed,and glass of any color and type from bottles, windows, glass used forbaking, and tableware can be used," Day says. The glasphalt was prepared ina commercial asphalt plant close to Rolla, and then placed using the sameequipment used for laying ordinary asphalt paving.

"Glass recycling is difficult throughout Missouri since there are only afew glass plants in the state which will purchase scrap glass or cullet,"Day says. "In addition, the buyers of scrap glass are often long distances-- 100 miles or more -- from the communities where the scrap glass isrecovered, so transportation costs can exceed the value of the glass."

All of the glass used in the airport project was collected from communityrecycling programs in south central Missouri.

"Glasphalt offers the advantages of being able to use those types of wasteglass which would otherwise be buried in landfills," says Dr. DavidRichardson, a UMR associate professor of civil engineering, who supervisedthe installation and evaluation of the glasphalt being used in the airportdemonstration project. "Glasphalt is also a means of disposing of verylarge quantities of waste glass and even for small projects like a parkinglot or street repair, which can use several hundred tons of waste glass."

In addition to demonstrating the usefulness and practicality of usingglasphalt for airport uses, the reflective properties of glasphalt willalso be evaluated. Glasphalt has been used extensively in Baltimore, Md.,for many years because the glass particles tend to reflect the streetlights and give the road surface a "sparkle."

"The higher reflectivity of a glasphalt runway could be an advantage atnight since the runway should reflect the aircraft's landing lights and bemore visible than an ordinary asphalt runway," Day says.

In addition, the tendency of glasphalt to dry faster after a rain thanordinary asphalt is an advantage for aviation use, and that will also beevaluated during the demonstration. The glass particles in glasphalt do notabsorb water like the rock in regular asphalt, Day says. "And in tests madeby the Missouri Highway Department, skid resistance of glasphalt was provento be 50 percent higher than typical asphalt, which is important toaviation when planes land and take off at high speeds," he says.

The paint used to mark the glasphalt runway also used waste glass ground toa fine powder. Dr. Harvest L. Collier, a UMR professor of chemistry, hasformulated and produced a "glass paint" that uses the finely ground glassas part of the pigments. The properties of the glass paint meet thespecifications for use on highways, but it has never been used for markingairport runways and taxiways. Because of the glass it contains, this paintmay also be reflective. The long term durability of this paint to weatherconditions will also be evaluated during the demonstration.

The information to be gained from this project and the technology beingdemonstrated could benefit many small Missouri communities that havedifficulty in disposing of waste glass and that want to avoid the cost ofputting the glass in a landfill.

"There are more than 180 small airports in Missouri, and thousandsthroughout the U.S., which could benefit from the results of this project,"Day says. "Glasphalt offers the opportunity to dispose of large amounts ofwaste glass in a way that could improve the general aviation airports insmall communities.

"These small airports often play an important role in industrialdevelopment," Day says.