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October 2000

News about Science, Technology and Engineering at Iowa State University

Christmas comes early for shelterbelt research
Taking down the Christmas tree could become a thing of the past. An Iowa State study on the use of artificial Christmas trees as shelterbelts (windbreaks) is determining how they may improve crop yields, prevent pesticide drift and suppress soil erosion on individual farms. Gene Takle, ISU professor of agronomy and geological and atmospheric sciences, said the Iowa State team has been working with shelterbelts for about 10 years, but this is the first year they've studied the potential of artificial trees.

"Through this research, we are trying to better understand details of turbulent wind flow around and through vegetation," Takle said. "From these observations, we are building complex computer models to simulate these flows."

Takle added that better understanding of such flows will help evaluate the role shelterbelts can play in the environment. The use of artificial trees allows researchers to manipulate the shape of the tree. This allows the group to test see how tree branch position affects sheltering.

"We rearranged branches to make cylindrical trees, sparse trees, and dense trees in addition to 'normal' trees," Takle said. He added that they can directly measure the force of the wind with these various tree shapes.

Iowa State is conducting the study with the University of Nebraska-Lincoln and the U.S. Forest Service. The ongoing shelterbelt research is supported by a $553,000 grant from the U.S. Department of Agriculture's National Research Initiative. For more information, contact Takle, (515) 294-9871, or Bridget Bailey, ISU News Service, (515) 294-6881.

New uses for lime sludge
A project at Iowa State University is showing some potential uses for lime sludge, a waste material from municipal water softening operations. The research -- by environmental engineering professor Hans van Leeuwen, and geotechnical and materials engineering assistant professor David White, both in the department of civil and construction engineering -- focuses on finding uses for a material that would otherwise have to be disposed of and typically adding 8-10 percent to the cost of water treatment. The two Iowa State researchers are looking at using the material in cement production, road construction and as a smoke-stack purification material for power plants.

"A cement manufacturer made 20 tons of cement using the lime sludge from a local water treatment plant," says van Leeuwen. "The cement was sold along with normal product. Also, this past summer at the Iowa State University power plant, we were able to use lime sludge for stack-gas purification rather than using limestone." Both of these demonstrations point to promising uses for this material, provided it is treated properly before its re-use.

In order to use the lime sludge as a purification material in the power plant demonstration, the sludge first needed to be dried to less than 2 percent moisture content. The research has shown that most of the moisture content of the sludge is "free water," meaning the sludge can be easily dried and there with a negligible amount of water re-absorption from atmospheric moisture. As power plants generate some waste heat, this could be used for drying the lime sludge, van Leeuwen said.

In the use of the lime sludge as a structural fill material, the researchers evaluated the crushing strength properties of lime sludge mixtures stabilized with various amounts of Portland cement and fly ash. Tests indicated more than sufficient crushing strength of the material could be obtained by adding either 10 percent Portland cement or 30 percent fly ash. The researchers found that the densities of these combined fill materials to be 20 to 30 percent less than typical soil materials, making them attractive for highway embankments and cutting down on transportation costs for fill material. Another use being investigated is the application of lime sludge to combat dust on unpaved roads.

"The project can be a benefit to many people by reducing the cost of water treatment, and benefit the environment by reducing solid waste quantities and lowering the need for limestone, an exhaustible resource," van Leeuwen said. For more information, contact van Leeuwen at (515) 294-5251, or Skip Derra, ISU News Service, (515) 294-4917.

Digging deep for gravel deposits
It's the old fashioned way to find gravel deposits. Hire a drilling company. Use a little common sense and try to find the much-needed mineral. That system has been used for many years. Igor Beresnev, associate professor of geological and atmospheric sciences, says that the old-fashioned way may be outdated.

Beresnev and his research team recently published a paper in the Journal of Applied Geophysics that uses modern technology for rapid reconnaissance surveys of gravel and sand accumulation. Natural aggregate (gravel) resources are used extensively in local-road maintenance and construction. Most municipalities face a constant need for the replenishment of diminishing reserves. The gravel must also meet certain quality and size standards as it must be firm enough and rigid enough to withstand vehicular traffic.

"A couple of years ago, Story County, Iowa, was running out of the reserves of gravel and sand they needed for secondary road repair," Beresnev said. "They wanted to explore new sites of excavation and wanted to know if there was a better way of locating these deposits."

Working with the Iowa Geological Survey, Beresnev looked at 10 potential locations in Story County where significant accumulations of gravel and sand might be located based on "surface expressions." Beresnev and his team utilized a 24-electrode resistivity imaging device to conduct fast and accurate surveys of those locations.

"We calibrate the method at an excavated site with the known gravel-layer geometry, and then apply it to surveying the sites of suspected but unknown potential," Beresnev writes. Of the 10 potential sites, only two of those proved to have significant accumulations of sand and gravel.

Finding the gravel and sand deposits is just one aspect to Beresnev's research findings. "Not only did we need to locate it, but we were able to provide accurate estimates of the volume of the deposits," he said. "This technology is cheap, fast and accurate. It would have taken a drilling company several days and thousands of dollars to find out the data we collected in just one day."

Beresnev confirmed his findings by drilling into the two gravel deposits.

"I'm very optimistic about the potential of using this technology in the future," he said. "I think we have solved a very practical problem. Sand and gravel are the number one mineral resources used in this country outside of oil." For more information contact Beresnev, (515) 294-7529, or Dave Gieseke, LAS Public Relations, (515) 294-7742.


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