ABSTRACT
The Canadian Standards Association is the leading specification writing organization in Canada, and the Standard A23.5 "Supplementary Cementing Materials and Guidelines for their Use in Concrete" covers the requirements for the use of fly ash, slag, and natural pozzolans in concrete. The inclusion of the accelerated pozzolanic activity index requirement is premature because of the lack of sufficient published data on the test method. The probable rationale is that because silica fume contains a high percentage of amorphous silica, it should be more effective in controlling the alkali-silica reaction in concrete. In the US, the ASTM is the leading specification writing organization, and the ASTM Designation C618 covers the specification for fly ash and raw or calcined natural pozzolan for use as a mineral admixture in Portland cement concrete. The Subcommittee responsible for this specification is drafting a revised C618 which will broaden the scope of the specification to allow the use of condensed silica fume.
