Microstructure and mechanical properties of β-hemihydrate produced gypsum: An insight from its hydration process

This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from fresh paste to hardened gypsum.The water demand of the investigated β-hemihydrate was determined applying the spread flow test. The flowability was studied and the deformation coefficient of the β-hemihydrate was derived accordingly. The hydration process of the β-hemihydrate was investigated applying an ultrasonic wave method and the influence of the water content on hydration was analyzed.The microstructure of the generated gypsum was studied by experiments and modeling. A model [1] was applied, which was successfully validated by the present experiments. Furthermore, the mechanical properties of the produced gypsum were investigated, and a numerical relation between water amount and strength was found.

Research highlights
► Water demand of β-hemihydrate was determined using spread flow test, and the influence of water content on the flowability was analyzed.
► The deformation coefficient of the β-hemihydrate was derived, the thickness of a water layer around the particles to assure the fluidity of the hydrating system was discussed, and the shape factor of the investigated β-hemihydrate was derived.
► The ultrasonic wave method is suitable for β-hemihydrate hydration measurement. A relation between the induction time and ending time of β-hemihydrate hydration and water content was found.
► A model was applied to describe the microstructure of the hydrating system, which was validated by experiments.