Representative material of ground granulated blast furnace slag (GGBFS, slag cement) was submitted for evaluation to verify a) the slag cement does not exceed the maximum allowable sulfide sulfur content and b) the addition of calcium sulfate. The upper limit for the sulfide content is specified in ASTM C989.

The total sulfur content was determined by the combustion method (LECO) without distinguishing between sulfide and sulfate. A pressed powder pellet was prepared next for XRF analysis to check for the presence of a characteristic sulfate sulfur Kβ X-ray emission line (satellite peak). XRF analysis could confirm that sulfur is present as sulfide and sulfate in the slag cement (B). The sulfate content was subsequently determined by the multiple standards addition method. The remaining question was whether the sulfate is present as gypsum, hemihydrate or anhydrite. X-ray powder diffraction could show that sulfate was added as anhydrite and that the slag cement was amorphous.

Detailed XRF scan showing the characteristic sulfur Kb emission line (satellite peak).

XRD pattern of the slag cement, confirming the addition of anhydrite.