STP1240: Alkali-Slag Cements For the Immobilization Of Radioactive Wastes

    Shi, C
    Environmental Process Engineer, Wastewater Technology Centre, Burlington, Ontario

    Day, RL
    Professor, The University of Calgary, Calgary,

    Pages: 11    Published: Jan 1996


    Abstract

    Alkali-slag cements consist of glassy slag and an alkaline activator and can show both higher early and later strengths than Type III Portland cement, if a proper alkaline activator is used. An examination of microstructure of hardened alkali-slag cement pastes with the help of XRD and SEM with EDAX shows that the main hydration product is C-S-H (B) with low C/S ratio and no crystalline substances exist such as Ca(OH)2, A1(OH)3 and sulphoaluminates. Mercury intrusion tests indicate that hardened alkali-slag cement pastes have a lower porosity than ordinary Portland cement, and contain mainly gel pores. The fine pore structure of hardened alkali-slag cement pastes will restrict the ingress of deleterious substances and the leaching of harmful species such as radionuclides. The leachability of Cs+ from hardened alkali-slag cement pastes is only half of that from hardened Portland cement. From all these aspects, it is concluded that alkali-slag cements are a better solidification matrix than Portland cement for radioactive wastes.

    Keywords:

    alkali-slag cements, immobilization, radioactive wastes, hydration products, leachability, pore structure, hydrothermal stability, chemical attack resistance


    Paper ID: STP14111S

    Committee/Subcommittee: D34.01

    DOI: 10.1520/STP14111S


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