Effects of moisture on the microstructure of cement-based materials. Progress report, September 15, 1991--January 15, 1993

摘要

New experimental techniques that allow the precise measurement of drying shrinkage of cement-based materials within the Environmental Scanning Electron Microscope have been developed. Accuracies of approximately 1% can be obtained on images as small as 20 (times) 20 pixels. Preliminary results on the shrinking of these materials has been obtained and quantitatively analyzed to produce ''maps'' of the deformation process. Samples have been dried from saturation in environments which a approximately 25% relative humidity, and deformation has been evaluated for the model materials C3S, C3A, and C4AF. The bulk of the effort during this initial period has been to establish the sophisticated experimental techniques which are necessary to pursue the proposed research. In this respect, the initial stage has been extremely successful and we have begun the process of detailed, methodical, documentation of the deformation of both the model materials and ordinary portland cement paste. The possibility of measuring the constraining effects of other phases such as aggregate is now being investigated. These initial results have resulted in four publications. Two publications are of a review nature and two are the reporting our new experimental technique, and initial results. The latter two are being submitted to peer reviewed journals.