T.e.m. studies of cement clinker compounds, their hydration and strong cement pastes

Abstract
Ion-beam thinned specimens of cement-forming compounds and cement pastes have been examined by transmission electron microscopy (t.e.m.). The triclinic lattice of pure tricalcium silicate has been confirmed and twins corresponding to domains of the superlattice have been observed. Thinned specimens of tricalcium aluminate show a copious amorphous reaction product at the surface after dipping into alkaline calcium sulphate solution, confirming the mechanism of retardation by blocking access to the surface. Observations of tricalcium silicate after it has been dipped into solution in contact with hydrating tricalcium silicate both with and without calcium chloride suggest that calcium chloride additive may accelerate hydration by improving access to the surface. Cement pastes of high strength (‘ macro-defect-free ’ pastes) show a similar fine-scale microstructure to cement pastes of low water content made by conventional techniques.