News Release, Kansas Geological Survey, Aug. 7, 2006
LAWRENCE--Researchers at the University of Kansas have developed a technique that could lead to more efficient quarrying of the limestone that goes into highway pavement and other types of construction.
The new technique incorporates a tool that measures the durability of one type of limestone used in construction, helping quarry operators predict immediately if the stone is durable enough.
The technique was developed by Robert Goldstein, chair of the KU Department of Geology, Evan Franseen, head of the stratigraphic research section at the Kansas Geological Survey based on KU's west campus, and Juli Emry, KU geology graduate student.
Crushed limestone is used in various construction materials, such as asphalt and concrete, that are known as aggregates. Low-quality aggregate in highways can lead to potholes and roads that need paving more often.
Identifying local sources of high-quality, durable limestone is critical, but they are increasingly difficult to find in many parts of the country, especially in areas where limestone is rare, or where urban areas are growing and have made it impractical to open new quarries close to construction sites. As a result, contractors often haul high-quality rock long distances, driving up costs. In some cases contractors are forced to use limestone that proves to be less durable than necessary, adding to the expense of replacing roads.
The durability of one type of limestone commonly used in aggregates is related to the amount of clay in the rock. Franseen and Goldstein have customized the use of a measuring instrument called a spectral scintillometer--basically a specialized Geiger counter--to tell quarry operators approximately how much clay is in a layer of limestone. In addition, the researchers developed a computer program that helps operators use those measurements to determine which limestone layers will produce durable aggregate.
"Limestone is a critical component of cement, asphalt, and other building materials, and the demand for high-quality, durable limestone for construction continues to increase," said Franseen. "Quarry operators need to know immediately if the ledge of rock they're quarrying is of good quality, and they need to be able to monitor quality as they continue quarrying that layer."
Current tests can require as much as six months to determine if a particular limestone layer is durable.
"Operators can't afford to wait that long to know if the limestone is good or not," said Franseen. "This is really a first-cut technique that can immediately evaluate the possible use of a limestone layer as a new quarry is opened, or to help keep track of quality as the ledge is mined."
The KU Center for Research is pursuing intellectual property protection on the technique incorporating the spectral scintillometer, and is now marketing it for development.