Changes in plaster microstructure by pre-stressing or by adding gypsum grains: microstructural and mechanical investigations

The setting and the mechanical behaviour of a coarse-grained plaster were investigated by means of different techniques: adiabatic calorimetry and measurements of swelling pressure and dimensional variations during the setting, fracture strengths and toughness evaluation, and scanning electron microscopy (SEM) observations. Subsequently the microstructure of the plaster was modified by seeding with gypsum grains of controlled size and concentration, or by applying a compressive stress (pre-stressing) during the setting. The correlation of the microstructural features and the mechanical properties confirms the interest in these methods for mastering the characteristics of a number of widely produced plaster-based materials.