Mix Design and Selected Properties of Concrete Containing Condensed Silica Fume

Bryan Magee, Mark Alexander

Research output: Contribution to journalArticlepeer-review


The paper describes a study carried out to investigate the use of South African condensed silica fume as a Portland cement replacement material in structural concrete. Aspects dealt with in the paper are fresh properties, strength development and the development of a mix design method. Results indicated a significant effect by condensed silica fume on all concrete properties. Concrete workability was found to reduce dramatically with increasing dosages of condensed silica fume. However, rates of workability decrease were found to be test-dependent. Reduced quantities of bleeding were recorded for concrete with increasing condensed silica fume replacement, and concrete strength development was greatly improved. A unique mix design method, capable of proportioning concrete with a range of condensed silica fume replacements for chosen values of 28-day strength and taking into account the water/binder ratio and dosage of condensed silica fume used, is proposed. Consideration is given to the practical implications of the work for concrete specifiers and producers.
Original languageEnglish
Pages (from-to)12-18
JournalJournal of South African Institution of Civil Engineers
Publication statusAccepted/In press - 1 Sept 1999


  • silica fume
  • mix design
  • concrete
  • performance
  • waste materials


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