Ultrasonic sound speed measurement as method for the determining the hydration degree of gypsum

摘要

This article addresses the sound velocity through slurries as well as non-porous and porousudmaterials. The focus is on using the sound velocity for the microstructure prediction of porousudmaterials, especially gypsum plasterboards, during and after hydration.udFor a slurry, the model of Robeyst et al. [1] showed a good agreement with experimentaluddata when taking into account an air content of 10 ml per kg of hemi-hydrate. This modeludtakes into account the bulk moduli of the continuous (fluid) and discontinuous (solid) phase asudwell as the size and shape of the solid particles. The bulk modulus of the fluid is corrected forudthe presence of entrapped air.udFor gypsum materials, the best agreement was found between the experimental andudtheoretical values using a series arrangement according to Ye [2] with a solid sound velocityud(cs) of 6800 m/s.udFinally, the sound velocity during the hydration of gypsum is studied. The use of linearudrelation between the amount of hydration-product (gypsum) formed and sound velocity givesuda reasonable result. Furthermore a relation between initial volume fraction hemihydrate andudhydration time is shown.