Proposed mechanism of C-S-H growth tested by soft X-ray microscopy

The reaction of silica particles in solutions saturated or supersaturated with respect to portlandite is observed by transmission soft X-ray microscopy, and a model for calcium silicate hydrate (C-S-H) growth is proposed which corresponds with the morphology observed in the Xray images. These images show a product that consists of bundles of dendrites that appear to diverge as the growth process continues, resulting in the formation of a characteristic morphology which is narrowest in the middle and broadened at the end - the "sheaf-of-wheat" morphology. In many cases, the dendrites appear to be oriented about a common axis, and it is proposed that this axis corresponds to a common origin in a single crystalline nucleus. (C) 2000 Elsevier Science Ltd. All rights reserved.