The findings associated with this project have wide-ranging effects on future engineering projects in Montana that use concrete. It provides engineering practitioners and students with valuable information and contributes to the ability to create projects with the correct concrete mixtures to ensure projects are safe and sustainable.
Billings, Montana
Billings Airport Commercial Apron Construction
Cracks in the Concrete
Morrison-Maierle’s team, while working on the Billings-Logan International Airport’s terminal expansion project, noticed a white gel and sprawled cracking on the concrete apron. On a previous project, they also witnessed concrete exploding into several little rocks when they demolished an old concrete ramp. Under normal circumstances, concrete breaks into several large solid pieces when it’s demolished, not small rocks. These two incidents led Morrison-Maierle’s team to conduct further investigations as they suspected Alkali-Silica Reaction (ASR) was occurring at the airport.
While the team tested a concrete mixture with fly ash and lithium that mitigated the ASR problem, Morrison-Maierle developed a phasing schedule for the new airport aprons. They also poured additional concrete slabs for commercial aircraft use while they removed the ASR-impacted concrete.
Client
Billings Logan International Airport
Location
Billings, Montana
Budget
$1.2M
Services & Highlights
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Construction administration
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Design engineering
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Field observation
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Lithium and fly ash pavement application
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Maintain flight schedules during construction
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New-to-Montana problem
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Phased project process
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Severe weather concerns
Alkali-silica reactivity (ASR) is a chemical reaction (between aggregate with certain forms of silica that reacts with alkali hydroxide) in concrete to form a gel. Photo courtesy of American Engineering Testing.
When water absorbs into concrete slabs, ASR produces a gel that expands and causes pressure on the surrounding concrete. Over time—with rain, humidity, and the ASR reaction—the concrete will start to explode.
ASR: A Problem New to Montana
Morrison-Maierle, as the airport’s engineer of record, contacted Montana State University (MSU) civil engineering researchers, who determined that up until now, ASR had not been detected in Montana. Common in other parts of the country, ASR is a chemical reaction in concrete. When water absorbs into concrete slabs, ASR produces a gel that expands and causes pressure on the surrounding concrete. Over time—with rain, humidity, and the ASR reaction— the concrete will start to explode, leaving debris on the surface, which is hazardous to airfields.
The project team kept six commercial aircraft locations open and operating at full capacity during the apron replacement project.
After the new concrete mix design was tested and approved for ASR, the existing concrete was replaced with a 16-inch concrete pavement section.
An Investment in Our Future
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