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Iowa State University--Becoming the Best

Aggregate Freezing-Thawing Performance Using the Iowa Pore Index


Principal investigators:

Co-principal investigators:

Project status


Start date: 08/01/15
End date: 10/31/16


Report: Aggregate Freezing-Thawing Performance Using the Iowa Pore Index (902.69 kb pdf) November 2016



About the research


In cold climates, the use of non-durable aggregate leads to premature pavement deterioration due to damage caused by freezing-thawing cycles. Differentiating durable and non-durable aggregates is a crucial yet challenging task. The frost durability of coarse aggregate has been reported to be related to its pore structure; however, existing test methods to identify pore structure are often not cost-effective. There is a need for a quick, reliable, and cost-effective aggregate test whose results correlate well with aggregate freezing-thawing performance.

The Iowa pore index test has been used by the Iowa Department of Transportation (DOT) for three decades as a supplemental decision making tool. This study investigated the relationship between the Iowa pore index and the freezing-thawing performance of aggregates as measured by three other test methods: Canadian Standards Association (CSA) A23.2-24A, Test Method for the Resistance of Unconfined Coarse Aggregate to Freezing and Thawing; ASTM C88, Standard Test Method for Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate; and an unconfined freezing-thawing test using conditioning according to ASTM C666, Standard Test Method for Resistance  of  Concrete to Rapid Freezing and Thawing.

The following results were observed: