A new hypothesis for air loss in cement systems containing fly ash

Lori E. Tunstall, George Scherer, Robert K. Prud'homme

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Although there are many benefits gained from incorporating fly ash into concrete, carbon contamination in the fly ash has been shown to interfere with the efficacy of organic additives in an unpredictable manner. This work uses surface tension measurements to quantify the adsorption of air-entraining agents (AEA) onto cement and fly ash. Both the adsorption capacity of the adsorbents and the adsorption isotherms indicate that the fly ash particles, rather than the carbon itself, dominate adsorption in a carbon-contaminated ash in cement pore solution. We propose that adsorption onto fly ash particles and cement actually improve air entrainment via Pickering stabilization. While the carbon is still expected to contribute to air loss via hydrophobic adsorption of the surfactants, we suggest that the primary way in which the carbon interferes is by shielding surfactant-coated fly ash particles from participating in air development and Pickering stabilization during mixing.

Original languageEnglish (US)
Article number106352
JournalCement and Concrete Research
Volume142
DOIs
StatePublished - Apr 2021

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • Materials Science(all)

Keywords

  • Adsorption isotherm
  • Cement
  • Fly ash
  • Particle or Pickering stabilization
  • Surface tension

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