Investigation of Proprietary Air-Entraining Admixtures to Produce Frost-ResistantConcrete with Low Air Content

摘要

This report covers a laboratory investigation of six air-entraining admixtures(AEA) to determine whether adequate frost resistance could be achieved in concrete with a water-cement ratio not exceeding 0.50 and air content less than the minimum value currently recommended by the American Concrete Institute. Concrete mixtures were proportioned and tested for resistance to freezing and thawing according to the provisions of American Society for Testing and Materials (ASTM) C 266, Procedure A as required by ASTM C 233. Durability factors were determined according to the provisions of ASTM C 666. Values for spacing factors and specific surfaces of the air-void systems were measured according to the provisions of ASTM C 457. When different AEA's were tested, the results indicated a significant difference in the frost resistance of concretes having the same air content. The AEA's with high air content provided adequate frost resistance; one AEA with medium air content provided adequate frost resistance; and none of the AEA's with low air content provided adequate frost resistance. The superior performance of one of the AEA's apparently resulted from smaller spacing factors and higher specific surfaces with lower air content than were present in other AEA's. At an equivalent air content, this AEA generated an air-void system comprised of smaller voids that were necessarily spaced closer together. The AEA's with low air content provided adequate frost resistance. The superior performance of one of the AEA's apparently resulted from smaller spacing factors and higher specific surfaces with lower air content than were present in other AEA's.