Carbonation and pH in Mortars Manufactured with Supplementary Cementitious Materials

Daniel McPolin, Muhammed Basheer, Adrian Long

    Research output: Contribution to journalArticle

    39 Citations (Scopus)

    Abstract

    An investigation of carbonation in mortars and methods of measuring the degree of carbonation and pH change is presented. The mortars were manufactured using ordinary portland cement, pulverized fuel ash, ground granulated blast-furnace slag, metakaolin, and microsilica. The mortars were exposed to a carbon dioxide-rich environment 5% CO2 to accelerate carbonation. The resulting carbonation was measured using phenolphthalein indicator and thermogravimetric analysis. The pH of the pore fluid and a powdered sample, extracted from the mortar, was measured to give an accurate indication of the actual pH of the concrete. The pH of the extracted powder mortar sample was found to be similar to the pH of the pore fluid expressed from the mortars. The thermogravimetric analysis suggested two distinct regions of transport of CO2 within mortar, a surface region where convection was prevalent and a deeper region where diffusion was dominant. The use of microsilica has been shown to decrease the rate of carbonation, while pulverized fuel ash and ground granulated blast-furnace slag have a detrimental effect on carbonation. Metakaolin has little effect on carbonation.
    Original languageEnglish
    Pages (from-to)217-225
    Number of pages9
    JournalASCE Journal of Materials in Civil Engineering
    Volume21
    Issue number5
    DOIs
    Publication statusPublished - May 2009

    ASJC Scopus subject areas

    • Building and Construction
    • Civil and Structural Engineering
    • Materials Science(all)
    • Mechanics of Materials

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