Electron probe microanalysis of gasifier slag cement pastes

The widespread use of cement replacement materials in concrete has generated interest in the potential use of gasifier slag (GS), a new replacement material with a chemical composition intermediate between that of ground granulated blastfurnace slag (GGBS) and pulverized fuel ash (PFA). A partial understanding of how the material behaves in concrete can be obtained through a study of the hydration of GS cements. New information on the hydration products has been gained by an examination of the composition of hydrates in GS cement pastes. Electron probe microanalysis has been used to study the composition of hydration rims around alite and slag grains in two GS cement pastes. The results are expressed in terms of atomic ratios, depicted graphically and compared with published probe data for GGBS and PFA cement pastes. The presence of GS modifies the composition of the hydrates in the rims around alite grains, particularly by the incorporation of aluminium. The composition of the hydrate around the GS grains is shown to be more similar to that around PFA than to that around GGBS grains.