Lafarage Canada Inc.

David B Oates

Donald Stephen Hopkins

Rayburn R Anderson

Paul H Lehoux

An unground, fine pozzolan having a sulphur content determined as wt. % SO.sub.3 of 5 to 25 wt. % is employed in admixture with Portland cement to provide a blended hydraulic cement which has increased compressive strength characteristics as well as extended retardation time without the need for separate addition of gypsum; the pozzolan may also be admixed with fly ash to provide a pozzolan blend for use with Portland cement with reduced Portland cement content and use of Class C fly ash; the pozzolan is derived by reaction of coal flue gases with an atomized vapor of slaked lime.

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Schomberg, Canada

David B Oates