Activation of rejected fly ash using flue gas desulphurization (FGD) sludge

X.C. Qiao, Chi Sun Poon, Z.S. Lin

Research output: Journal article publicationJournal articleAcademic researchpeer-review


Low-grade fly ash (rejected fly ash, rFA), a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process, remains unused due to its high carbon content and large particle size (> 45 mum). But it is thought that the rejected ash may have potential uses in chemical stabilization/ solidification (S/S) processes which need relatively lower strengths and a lower chemical reactivity. Flue Gas Desulphurisation (FGD) sludge is a by-product of air pollution control equipment in coal fired power plants whose chemical composition is mainly gypsum. As there is no effective usage of both of these two materials, it is of interest to research on the possible. activation of rFA using FGD. This paper presents experimental results of a study on the properties of rFA activated by the FGD in rFA-cement pastes. Different percentages of FGD were added into the mix to study the effects of the FGD on the reaction of the rFA blended cement pastes. The results show that FGD takes effect as an activator only at late curing ages. Adding Ca (OH)(2) enhances the effect of FGD on activating the hydration of rFA. Also, 10% FGD by weight of rFA is the optimal addition in the rFA-cement pastes. The results of the compressive strength measurements correlate well with the porosity results.
Original languageEnglish
Pages (from-to)84-88
Number of pages5
JournalJournal of Wuhan University of Technology. Materials science edition
Issue number4
Publication statusPublished - 2003


  • Rejected fly ash PFA
  • Strength development
  • Activator
  • Flue gas desulphurization sludge
  • FGD

ASJC Scopus subject areas

  • General Materials Science


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