New applications are reviving old technologies that combine thermoset polymers and concrete, and industry groups are taking notice.
The domestic polymer concrete market is growing 20-25 percent annually and has more than doubled in the past four to five years, John Downing, general manager of Strongwell's polymer concrete division in Lenoir City, Tenn., said in a telephone interview. The unit of Bristol, Va.-based Strongwell makes utility boxes, industrial floor blocks, surface drain systems and tunnel and bridge rehabilitation products.
Excluding bridge deck work, precasts use about 15,000 tons of unsaturated polyester resins and 2,500 tons of epoxies and vinyl esters annually, according to Jim Maass, vice president of cast polymers with material supplier Reichhold Inc. in Research Triangle Park, N.C.
Including bridge work, the industry uses about 25,000 tons of the polymers per year in the United States and 100,000 tons worldwide, said Al Kaeding, vice president of engineering with precaster CDR Systems Corp. of Ormond Beach, Fla.
Kaeding also is chairman of the American Concrete Institute International's committee on polymers and concrete.
U.S. sales of precast products are about $75 million per year, according to Arthur Dinitz, president of Transpo Industries Inc. in New Rochelle, N.Y. Transpo makes precast products, prepackaged filler systems and an in-the-field resin system for patching bridges and repairing concrete.
Ease of use, versatility and economy favor unsaturated polyesters, which may include PET regrind. Corrosive environments, such as copper mines, require vinyl esters. Resin content can range from 5 percent for methacrylate, 8-22 percent for polyester and 25 percent for low-shrink, easy-to-formulate epoxy.
In comparison, polymer concrete wins on lightness and bonding capability but loses to Portland cement concrete on cost.
Polymer concrete dampens base vibrations of drill presses and other machine tools and may replace telephone poles and railroad ties. A collectibles niche includes garden statuary, stepping stones and weather-resistant yard signs.
Maass said the industry ``is enjoying healthy growth in traditional markets'' involving below-grade precast utility boxes that protect residential gas- or water-main controls, access covers and sleeves and highway drains and gutters.
Still, conflicts over cost, culture and concept slow adoption of polymer concrete in some public arenas.
High upfront costs of polymer concrete deter highway officials, although life expectancy is four or five times as long as conventional materials, Maass said.
Highway use ``will be a big market when it takes off,'' Maass said.
David Fowler blames culture.
``The chemical companies need to go through smaller companies and distributors if they do not understand the construction culture or if they do not have a sales organization to service the construction industry,'' Fowler said.
``Unknown materials [can] scare highway contractors, and the chemical companies see the road workers without safety apparatus or gloves,'' said Fowler, an engineering professor at the University of Texas at Austin.
``I'm having a hard time getting those [highway] guys in Texas to use polymer concrete,'' Fowler said. ``Partly, people [were] burned with it'' years ago, when epoxy was dropped improperly into potholes.
``The pure epoxy had a coefficient of expansion 10-12 times that of concrete, and in a few months the entire epoxy patch would come out in one piece with concrete bonded to it,'' he said.
Specialists and professionals will talk about materials microstructure, behavior modeling, advanced structure reinforcement and testing during the International Congress on Polymers in Concrete technical conference, being held Sept. 14-18 in Bologna, Italy.
On Oct. 20, ICPIC and the Composites Fabricators Association plan a day-long, business-oriented program on polymer concrete in San Antonio, Texas. The meeting is in advance of CFA's Composites '98, scheduled for Oct. 21-24.