Direct adsorption isotherms of AEAs and fly ash: α-olefin sulfonate and combination admixtures

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© 2015 American Chemical Society. The direct adsorption isotherm test provides a direct measurement of the air entraining admixtures (AEAs) adsorption by fly ash in concrete. This method was developed and tested using a popular Vinsol resin admixture. In this paper, the direct adsorption isotherm test was performed on two other commonly used AEAs of different chemical compositions to verify the applicability of this method to AEAs of other chemical natures. The results showed that, as in the case of the Vinsol resin admixture, the AEAs partitioned between the solid and liquid phase, the partitioning coefficient changed with changing the AEA concentration, and this method was able to quantify the fly ash adsorption capacity based on the Fruendlich adsorption model. Also, in order to present a practically useful approach for the concrete/fly ash industry, the isotherms results of the three AEAs were correlated to the fly ash iodine number test results. Concrete producers can use these correlations to determine the AEA adsorption capacity, and the AEA dosage adjustment using the fly ash iodine number without the need to perform the direct adsorption isotherm test.

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ACS Sustainable Chemistry and Engineering