Ash-Based Aggregate

West Mifflin, Pa.-based Universal Aggregates designed, constructed and currently operates a 3,500-sq.-ft. plant at the Birchwood Power Facility in King

Steven Prokopy

West Mifflin, Pa.-based Universal Aggregates designed, constructed and currently operates a 3,500-sq.-ft. plant at the Birchwood Power Facility in King George County, Va., that turns spray dryer ash (from a nearby coal-burning power plant) into lightweight aggregate for use in masonry blocks, concrete and asphalt paving material.

Although plant construction was completed in May 2004, initial plant integration did not begin until November. From preliminary integration and operation, several key process components were isolated for modification and improved performance. After all upgrades were complete, Universal began true integrated plant start-up in September 2006.

The facility operates on 5.5 acres of land adjacent to the 240-MW Birchwood plant, which generates approximately 150,000 tons of spray dryer ash each year. At full production, Universal Aggregates will turn this ash into 167,000 tons of manufactured lightweight aggregate per year, although the operation is currently operating at about 60 to 65 percent of capacity. We should be at 100 percent by the end of this calendar year, says Paul Yuran, Universal’s manager of marketing and product development. But, we sell everything we produce.

The company’s primary customer base is masonry producers, including Ernest Maier Block of Bladensberg, Md.; Parker Block, also in Maryland; and, Betco-Supreme, an Oldcastle company based in Manasas, Va. We also get good results in structural concrete, adds Yuran, but we have yet to really push in that direction in terms of marketing, but we have a strong desire to do so.

In late 2001, Universal was one of eight companies to receive a U.S. Department of Energy grant earmarked for clean coal technologies within DOE’s Power Plant Improvement Initiative. The $7.2 million went into demonstrating the lightweight-aggregate production process, which is also able to utilize fly ash, flue gas desulfurization sludge, and fluidized bed combustion residues. At the time, the company was a joint venture of Pittsburgh’s Consol Energy Inc., and SynAggs. In 2003, SynAggs’ owners (a family-operated business affiliated with P.J. Dick Contracting and Trumbull Corp.) bought out the Consol stake from a German parent company.

Ash from the Birchwood facility is a by-product of the power plant’s spray dryer scrubber system. Scrubbers are used on many coal-fired power plants in the United States to reduce sulfur pollutants, but only about 30 percent of the 28 million tons of residue produced each year is reused.

In the Universal Aggregates process, ash from the spray dryer and other solid wastes from the power plant are blended in a mixer to produce a uniform granular material. The loose, moist composition is then fed to an extruder that further mixes the material and forces it through the holes of a metal die to form wet green pellets, which are dried and hardened in a curing vessel specially designed to allow the solids to flow continuously without hanging up. One of the unique aspects of our operation is that it’s a low-temperature curing process [150_ to 170_F], and no combustion source is required, explains Yuran.

After curing, the hardened pellets are crushed and screened to specification, then stockpiled for sale as manufactured aggregates.

As new environmental standards take effect, power companies are expected to install more scrubbers, which will improve air quality and inevitably increase scrubber waste tonnage, placing greater burdens on landfills and other disposal methods. The Universal Aggregates method is designed to address that trend. All of our customers are interested in the recycled-content angle of this material, says Yuran. We just met with a representative from Oldcastle who really emphasized that they liked this. Whether they have taken that aspect of our material and attempted to get LEED [Leadership in Energy and Environmental Design] credits, I don’t know. But our product does qualify for the credits as recycled material.

One thing Yuran and his team learned early on in designing and experimenting with this process is that there’s a major difference between running a pilot plant for a few masonry producers and operating such a plant for commercial use. For the first two years, we operated as a pilot plant. We took our aggregate to masonry producers and had them do testing, and nobody threw me out, which was good, he says. But I’ll admit, we had mixed results at first. Initially, we had to make modifications to off-shelf equipment to improve this process, and some of that equipment was made for other industries and was not standard. We had to work with equipment makers and users to perfect the process.


Top, Elite Aggregates material uses as much as 45 percent bottom ash and up to 45 percent expanded polystyrene, plastics, and class C or F fly ash. Bottom, concrete pavers made from ASTM 331-standard Elite Aggregates.

One synthetic lightweight aggregate that appears to be on the verge of breaking through in U.S. markets comes from Centennial, Colo.-based Elite Aggregates, which to date has been issued three patents for its product and process. The high-strength aggregate is manufactured from recycled materials, and can be considered an environmentally friendly replacement for mineral-based lightweight aggregates, while offering a significant economical advantage to users.

Meeting ASTM C-330 (structural concrete) and ASTM C-331 (masonry units) standards for mineral-based lightweight aggregates, Elite uses as much as 45 percent by volume of bottom ash and up to 45 percent expanded polystyrene, plastics, and class C or F fly ash, thus reducing the amount of these solid waste materials dumped into landfills.

Explaining the benefits and cost advantages of block companies acquiring the licensing of this process, Elite CEO David Shulman explains, We are able to use recycled materials; synthetic lightweight aggregate commands a high price on the market; and, with only a few front-end modifications, we can use block machines already in use.

Based on his research, Shulman estimates that synthetic aggregates could replace 10 to 15 percent of the current domestic aggregate market, producing revenues in excess of $2.5 billion dollars in the United States alone.

Elite Aggregates’ product weighs between 34-54 lb./cu.ft. with a compressive strength of 3,500 psi. The resulting high-strength concrete can be cut, screwed and nailed with standard construction tools. Using the material as the aggregate base in various concrete mixes yields compressive strengths of 5,000 psi at 95.8 lb/cu.ft. and a tensile strength of 535 psi. Standard concrete blocks with compressive strength of 2,000 psi weigh about 40 lb., while block made with the synthetic aggregate and same psi weighs about 22 lb. We also have something called ultra-strength lightweight concrete, says Shulman, which is a 9,000-psi compressive strength mix weighing about 98 lb.

Before its patents could be issued, Elite Aggregates had to acquire a certificate for Proof of Process of Manufacturing and Aggregate Testing through Commercial Testing Laboratory of Denver. The company also did extensive testing at the World Center for Concrete Technology in Alpena, Mich.

The marketing of this technology has been focused on three areas: power plant groups looking to manage their ash byproduct; the block industry, which could adapt to this process; and, larger aggregate companies, since the crushed product can also be used as an aggregate replacement. We would license out the process to distinct territories in the country, near power plants, says Shulman. We give the customer a locked-in location that guarantees a sufficient daily supply of raw materials for at least an eight-hour shift. Û