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Abstract
In this work a detailed study on the formation of the stoichiometric and the sulfate deficient ettringite is presented. The expansion of the ettringite-bearing solids, as well as of ordinary Portland cement clinker doped with these phases in different curing media is investigated
The ettringite phase is obtained from stoichiometric sulfate media through the reaction of calcium hydroxide suspension with aluminum sulfate solution at room temperature. In the sulfate-deficient media gibbsite was added to keep the stoichiometric alumina concentration. The results obtained proved the formation of the ettringite in both media. The investigations were based on the data obtained from X-ray diffraction analysis, scanning electron microscopy with EDAX attachment as well as the wet methods of chemical analysis.
The expansion behavior of the ettringite-bearing solids obtained from the different sulfate media showed a greater susceptibility of expansion for the samples with the ettringite obtained from the stoichiometric sulfate media compared to those of the sulfate deficient ones. The same sequence was observed for the clinker doped with the ettringite -bearing solids. The curing media were: Different concentrations of sodium sulfate solutions, lime solution, alkali hydroxide solutions and water.