The nature of C-S-H in model slag-cements

Model systems have been used in a large number of studies concerning the chemistry of the hydration of Portland cement. These have most commonly involved tricalcium silicate (C3S) but C3S has also been mixed with other components in studies on a variety of composite cements. This paper compares the nature of the C-S-H formed in real slag-cement blends with model systems involving C3S. The hydration products and microstructural features present in the model and real systems are broadly similar. In both, the morphology of outer product (Op) CS-H changes from 'fibrillar' to 'foil-like' as the slag content is increased. The Ca/(Si + Al) ratios of inner product (Ip) and Op C-S-H are similar in real slag-cements but are different in the model systems; the difference becomes a little less pronounced at higher slag content. The aluminosilicate anion structures of the C-S-H phases present in the model and real cements are similar with 90% slag but very different with 50% slag. (C) 2000 Elsevier Science Ltd. All rights reserved.