Nondestructive determination of drying deformations in cement paste by means of ESEM and digital image analysis

Novel modifications of an environmental scanning electron microscope (ESEM) were made in order to measure the local deformations in drying cement paste. These nondestructively determined moisture-induced plane strains, obtained in 1 mm thick cement paste samples, are orthotropic. They vary with variations of relative humidity between 70%-80% and 40%-50%, being the highest at 20% RH. Both drying shrinkage and expansion of cement paste microstructure occur in early-age and mature samples. Microcracking due to moisture gradient could not be avoided, although very thin samples were examined with gradual reduction of relative humidity in drying steps of 10%. The coefficient of deformation of cement paste is directly proportional to shrinkage/expansion. It depends on variations of relative humidity during drying in ESEM and the sample age.Micro Mechanic LaboratoryCivil Engineering and Geoscience