Relationship of the garnet-hydrogarnet series to the sulfate resistance of portland cements

Abstract

Isometric 3CaO.AhOa.6H20, a constituent of set portland cement, is readily converted by sodium sulfate solutions to 3CaO.AI20 a.3CaS04.31.5H20. Partial replacement of the Al20 a in 3CaO.AI20 3 .6H20 by Fe20a or of the H20 by Si02 gives "hydrogarnets" which are stable in the presence of sulfate solutions. Such substitutions may be brought about by inducing reactions between tricalcium aluminate hydrate and silica from various sources in the set cement or from added puzzolanic materials, and by increasing the content of glass and tetracalcium aluminofel'rite in the cement.