Faculty, students receive recognition from leading civil engineering journal

Jennifer Matthews
July 11, 2019

UNIVERSITY PARK, Pa. — A research paper submitted by faculty and students in the Department of Civil and Environmental Engineering at Penn State has been honored with the 2019 Outstanding Article Award by the American Society for Testing and Materials (ASTM) Journal of Advances in Civil Engineering Materials. This premier civil engineering journal covers all aspects of material processing, structure, properties and performance in civil engineering systems.

Mina Mohebbi, a recent doctoral graduate in civil engineering at Penn State and assistant professor of civil engineering at Middle Tennessee State University; Farshad Rajabipour, associate professor of civil engineering at Penn State; and Barry Scheetz, professor emeritus of civil engineering at Penn State, received the honor for their paper titled “Evaluation of Two-Atmosphere Thermogravimetric Analysis for Determining the Unburned Carbon Content in Fly Ash,” which was published in Volume 6, Issue 1, 2017 of the journal.

Fly ash is a coal combustion product composed of noncombustible mineral impurities in coal and is driven out of power plant boilers as fine particulates. It is removed from the flue gases by particulate emission control technologies and is subsequently used in Portland cement concrete if it meets certain composition, property and performance requirements.

“Fly ash is a key ingredient of concrete and is used to improve the workability, sustainability and long-term durability of concrete mixtures,” Rajabipour said. “It is a promising alternative to Portland cement to reduce the embodied energy and CO2 footprint of concrete. One challenge with fly ash is the presence of unburned coal/carbon (UC) particles, which interfere with producing high-quality concrete. As such, the correct measurement of the UC content of fly ash is important to reliably identify ‘bad’ fly ashes without unnecessarily discarding any of the ‘good’ ashes.”

Improving this process is critical as the overall supply of fly ash is shrinking due to coal power plant closures and the ever-increasing difficulty of keeping up with demand from the construction industry.

Current tests, including the loss on ignition (LOI) test, are commonly used to estimate the unburned carbon content; however, the LOI test is not very accurate, so the researchers chose a thermogravimetric analysis (TGA), which carefully monitors off-gassing and mass loss of fly ash as it’s heated. They paired that with mass spectrometry, allowing them to evaluate the thermal decomposition reactions that occur in fly ash to measure the true unburned carbon content. This new method allows better separation of the UC from other sources of mass loss in fly ash.

The results showed that LOI overestimated UC by up to 6.4 times, meaning that many otherwise good fly ashes are excluded from the concrete market because of an unreliable LOI test.

The knowledge gained as a result of this work shows how various TGA test parameters impact the accuracy of results. This study will help researchers design the optimal testing protocol with the ultimate goal of adoption by governing specifications and standards organizations such as ASTM.

Funding for this study was provided by the Pennsylvania Coal Ash Research Group, which is a consortium of power utility companies, fly ash marketers and consultants in Pennsylvania.

“The Outstanding Article Award by ASTM Journal of Advances in Civil Engineering Materials is an exceptional honor given to only one paper out of more than 100 that are published by this prestigious journal every year,” Rajabipour said. “It is a wonderful privilege to be recognized for the quality and impact of our work and will give us an emotional boost to continue to do bigger and better in the future.”

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Last Updated July 12, 2019