Volume 7, Issue 2 (February 2010)
Determining the Air-Entraining Admixture Dosage Response for Concrete with a Single Concrete Mixture
Currently there is no standardized test method to determine the interaction of the ingredients of a concrete mixture with a dosage of air-entraining admixtures (AEAs). Typically, to investigate the AEA demand, multiple concrete mixtures are made with varying dosages of AEA, and the resulting air contents are measured. This method is not ideal as it is time consuming, uses large amounts of material, and allows several variables to change that could cause changes in the dosage response of the mixture. A method is presented that is able to measure the AEA dosage response of a mixture through a correlation between the gravimetric (ASTM C138-01a) and pressure method (ASTM C231-03) with only minimal changes to the volume of the mixture. This allows the AEA demand to be determined from a single concrete mixture rather than sequential mixtures. Testing results are also provided for concrete mixtures containing fly ashes with various AEA demands. These mixtures are evaluated for changes in AEA demand with water reducer, mixing temperature, fly ash replacement level, and type of AEA.