Geopolymers, inorganic compounds with better compressive strength and flexibility than reinforced cement, have the potential to replace traditional cement for military, commercial, and domestic applications—from buildings to roads and airport runways.
Dr. Ben Varela, associate professor in the department of mechanical engineering in the Kate Gleason College of Engineering, is working with the United States Air Force Office of Scientific Research to test the feasibility of using geopolymer materials for military applications. Varela visited Wright-Patterson Air Force Base in Ohio to complete a series of tests on the development of the composite material.
Geopolymers are inorganic materials, synthesized from kaolins or fly ash, prepared with alkaline solutions and soluble silicates. The formula has the consistency of a dense paste that starts to solidify in a matter of hours, compared to days needed for traditional cement.
"Depending on the composition, you can have a solid block within a couple of hours, with strength measuring 3,000 psi," Varela explains. PSI, or pounds per square inch, is a measurement of pressure on the structural block. Comparatively, cement may reach that level of strength, but it takes 28 days.
"That is what the Air Force was interested in. If we can cast a runway, we can potentially have airplanes landing in less than a day," says Varela. "We use concrete for many applications, but concrete is not as stable at high temperatures. It deteriorates at 450 degrees Celsius. In fires, that is the cause of the collapse of the structure. In the case of geopolymers, my experiments show they are stable up to 1,000 degrees Celsius and we are looking to raise that level even higher."
The process to manufacture geopolymers also requires less energy because it is done at a lower temperature than cement, 65 degrees Celsius, saving energy in the overall process. "The production of cement and concrete produces a large amount of carbon emissions. It is estimated that for every ton of cement we produce, we also produce one ton of carbon dioxide," says Varela. Cement manufacturing is one of the largest emissions producers of carbon dioxide to the atmosphere. Geopolymers may be an alternative to the use and manufacture of structural materials.
"We are finally realizing the potential of geopolymers and we are catching up with the research being done in Australia and Europe very, very fast. We are only one of a few research groups in the U.S. but interest is picking up and there is a potential now to retrofit some structures such as roads and bridges," adds Varela.