Researchers evaluated the relationship between aggregate carbonate content, freeze-thaw durability and properties such as pore structure and absorption to determine whether some aggregates currently rejected by MnDOT might be used in concrete mixes. Laboratory testing of aggregates showed that a 30 percent limit on carbonate content may not be necessary since this content did not predict freeze-thaw performance. Aggregates containing more than a 30 percent carbonate portion might be used to produce a freeze-thaw durable pavement if the carbonate portion aggregate has a good pore structure, low absorption and high specific gravity.