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Published online by Cambridge University Press: 21 February 2011
The hardening shrinkage of calcium aluminate based ultra-high strength cement becomes nearly zero by using calcium sulphoaluminate compound, and very high bending strength can be obtained by calcinating at 300°-600°C. The starting materials are calcium aluminate, silica fume, calcium sulphoaluminate compound and superplasticizer, and the water-to-power ratio is 0.15–0.25. The main hydration products are C3AH6, AH3, C-S-H and ettringite, forming a densely packed structure, together with a large amount of unreacted cement particles. The hardening shrinkage is remarkably reduced, because of the ettringite formation in the early stage. The bending strength is about 55 MPa when calcined at 600°C. C12A7 is identified by XRD; needle-shaped skeletons of ettringite crystals are observed by SEM. It is suggested that chemically bonding substances are C12A7, amorphous A12O3, and C-S-H in calcined calcium aluminate based DSP with ettringite.