DRYING SHRINKAGE OF CEMENT PASTE AS MEASURED IN AN ENVIRONMENTAL SCANNING ELECTRON-MICROSCOPE AND COMPARISON WITH MICROSTRUCTURAL MODELS

A recently developed image-intensity-matching technique has been used to analyse images of cement paste which were dried in an environmental scanning electron microscope. Shrinkage that occurs during changes in relative humidity is reported, together with some of the influences o f water-to-cement ratio, temperature and age. Results from microstruct urally based models are compared with experimental results. The best f it of models to experiment is achieved if calcium silicate hydrate (C- S-H) is divided into two types: high density C-S-H, which does not shr ink, and low density C-S-H, which does shrink. Approximate values of u nrestrained shrinkage of the low density C-S-H are attained as a funct ion of relative humidity.