According to the NJIT researchers, the fly ash concrete achieves the same strength as conventional concrete in the same time frame, 5 to 10 days, and thereafter becomes about 30% to 40% stronger.

      For utility plants and other facilities that generate the estimated 80-million tons of fly ash produced annually in the United States, the research promises to trade the expense of removing and dumping an industrial byproduct in landfills with profit from fly ash sales.

      For construction industry purchasers of cement, the NJIT results promise cement that not only makes stronger concrete but costs less since up to 35% of cement content can be replaced with inexpensive fly ash.

      So far, the new fly ash cement has earned four patents: two for its properties for curing or gaining strength as rapidly as conventional cement in a concrete mix, a third for a refinement that enables up to 95% of all fly ash to be used to make cement, and a fourth patent for fly ash concrete that is resistant to acid attack. The last is seen as particularly useful for sewer pipe construction since organic waste generates hydrogen sulfide that subsequently converts to sulfuric acid.

      Fly ash is a combination of silica and calcium oxide/hydroxide that when mixed with cement causes a reaction known as the pozzolanic effect. In the pozzolanic effect, calcium oxide and hydroxide --the lime elements -- combine with the glass-like silicon elements to add strength to cement.

      While the pozzolanic effect has been known for over 60 years, its usefulness was limited because no one knew how to control the process to get the best possible results.

      Notes NJIT Research Team Leader, Civil and Environmental Engineering Professor Methi Wecharatana, "Fly ash was often treated as a 'black box'. Most users didn't know where it came from, how it was burned, or what was really in it. Then they dumped it into concrete, which was another 'black box,' and prayed for good results."

      Since little was known about fly ash cement's concrete- strengthening properties, there was no guarantee that it would perform properly. "It couldn't be used with much confidence because there was no quality assurance nor day-to-day consistency," says Wecharatana.

      Equally important, fly ash concrete was impractical for most construction industry applications because its strength didn't become apparent for about 60 to 90 days, much longer than the seven to 14 days needed for conventional concrete. Construction couldn't proceed until the concrete hardened and concrete forms could be removed safely.

      Supported by funding from the Department of Energy (DOE), Public Service Electric & Gas Company (PSE&G), and other sources, Wecharatana's team studied the "black box" of fly ash.

      The team discovered that - aside from the pozzolanic effect -- the cut, size and distribution of fly ash particles also impact the strength of cement. What's more, they can provide a benchmark to predict the performance of different varieties of fly ash.

      Notes Prof. Wecharatana, "We did a very refined study, cutting and sorting fly ash into different sizes - zero to five microns, 5 to 10 microns, all the way to 50 microns to find out how each size performed."

      The team found that very fine fly ash particles - such as those in the zero to 5 micron range -- strengthen cement because they seal up the voids between individual cement grains, making the cement even more dense and hard. "Together with the pozzolanic effect, the smaller fly ash particles firm up the matrix of cement grains," says the NJIT professor.

      Armed with the ability to predict performance, Prof. Wecharatana's team was able to develop a concrete mix in which up to 35% of cement content was replaced by fly ash. In addition, the mix cured within seven to 10 days instead of 90-plus days, and was 30 to 40% stronger than conventional concrete.

      "This was a real breakthrough in pricing as well as performance," notes Wecharatana. "Cement costs roughly $50 to $60 a ton, while processing fly ash costs about $10 to $20 a ton."

      At first, the NJIT team found that only about 35% to 40% of all fly ash was suitable for making concrete. However, with further processing refinements the team was able to use about 95% of all fly ash. "This meant that if someone gave us 10 tons of fly ash, we were now able to get 9.5 tons of good quality ash for making concrete that performs better than the standard product," Wecharatana notes.

      Further NJIT research revealed that certain combinations or mixes of fly ash can be used to make concrete ideal for sewer construction. Conventional concrete sewer piping must be lined with an expensive polymer coating to protect it from the sulfuric acid generated by decaying organic waste.

      NJIT research revealed that certain combinations or mixes of fly ash concrete offered strong resistance to sulfuric acid. The key was the lime in cement; conventional cement has a lot of free lime - lime that's not bound by another element and available for attack by acid. When the lime is degraded, the concrete erodes.

      In certain combinations of fly ash cement however, the fly ash binds with most of the lime and protects it from attack by acid.

      Wecharatana says that the next step will be commercialization of the fly ash process. He notes that several cement companies have expressed interest in it, as have utilities like Public Service Electric & Gas (PSE&G)and GPU.

      Considering the estimated 80 million tons of fly ash generated annually in the U.S., turning fly ash into a viable product could add up to several billion dollars a year generated from profit gained and dumping costs saved.

      NJIT is a public research university enrolling nearly 8,200 bachelor's, master's and doctoral students in 87 degree programs through its five colleges: Newark College of Engineering, New Jersey School of Architecture, College of Science and Liberal Arts, the School of Management and the Albert Dorman Honors College. Research initiatives include manufacturing, microelectronics, multimedia, transportation, computer science, solar astrophysics, environmental engineering and science, and architecture and building science.

      Yahoo! Internet Life magazine has ranked NJIT as America's "most wired" public university for two consecutive years, U.S. News and World Report's 1999 Annual Guide to America's Best Colleges ranked NJIT among the nation's top universities, and Money magazine's most recent issue of Best College Buys rated NJIT as the sixth best value among U.S. science and technology schools and among the top 100 overall. In September 1999, Mademoiselle ranked NJIT as the second most Internet-connected university in the nation.