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    STP1033

    Leaching-Induced Concentration Profiles in the Solid Phase of Cement

    Published: 0


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    Abstract

    Analysis of the solid phase of portland cement specimens by energy-dispersive X-ray spectrometry before and after leaching provided elemental profiles within the cement. Releases of potassium were calculated from the solid-phase profiles and were compared with releases determined from leachate analyses of potassium and cesium-137. The fraction of potassium released in the leachate was found to correlate closely to that of cesium-137 under varying time and temperature conditions, despite the different manner in which each was originally contained in the cement. Agreement was obtained among potassium releases as determined from the solid, potassium in the leachate, and cesium-137 in the leachate. These correlations allowed the use of potassium as an analog for cesium-137 in cement.

    Profiles of potassium in the solid showed varying degrees of depletion. A specimen, sectioned immediately after leaching for 471 days, contained no observable potassium to 9 mm depth from the specimen surface. From 9 mm to the center of the specimen, an apparently linear increase in concentration was observed. Specimens that had been air-dried prior to sectioning had profiles that were produced by evaporative transport of dissolved species toward the surface. Carbonation of the surface appears to have retarded migration of the dissolved material. This prevented it from reaching the outer edge and resulted in increased potassium concentrations several millimetres inside the surface.

    Keywords:

    leaching, portland cement, solid phase analysis, potassium, cesium-137


    Author Information:

    Fuhrmann, M
    Geochemistry associate and chemist, Brookhaven National Laboratory, Associated Universitites, Inc., Upton, NY

    Colombo, P
    Geochemistry associate and chemist, Brookhaven National Laboratory, Associated Universitites, Inc., Upton, NY


    Committee/Subcommittee: D34.01

    DOI: 10.1520/STP22888S