Much of the crushed limestone aggregate produced in the Oklahoma region is susceptible to freeze-thaw action and can result in popouts and D-cracking in concrete. Four series of tests involving over 120 batches of concrete were conducted to establish if adjustment of certain mix parameters would mitigate the detrimental properties of the aggregate. Freeze-thaw tests were conducted in accordance with Procedure A of ASTM C 666. The first series of tests demonstrated the importance of the maximum size of coarse aggregate on the durability of concrete. By reducing the maximum size from 1 in. to 1 /2 in., durability factors were increased from approximately 40 to 80. The second series of tests revealed that if the water-to-cement ratio is reduced below the range normally used for pavement construction, durable concrete can be made with ma rginal aggregate. The third and fourth series considered the addition of Class c fly ash or silica fume to the mix. In the case of Class C fly ash, concrete made with marginal aggregate from one source experienced no major influence from the presence of fly ash. The durability of the concrete increased with an increase of compressive strength regardless of the fly ash percentage. However, with concrete made with aggregate from another source, durability remained low regardless of strength. Silica fume did not appear to significantly alter the durability of concrete.Final Report January 1986-June 1991N
