An electron optical examination of zoning in blastfurnace slag hydrates: Part I. Slag cement pastes at early ages

This paper is the first of three which examine the composition and development of zoning in slag hydrates in blastfurnace slag cement pastes and concrete specimens using optical and electron probe techniques. It describes the early development of zoning in the hydration rims around the slag grains. In cement pastes containing small or larger additions of slag, some of the slag hydrates are marked by compositional zoning. This type of zoning represents the occurrence of two or more layers of slag hydrates with each layer containing different amounts of a hydrotalcite-type phase and an impure CSH. The composition of the individual layers is not repeated within the same slag rim.