We examined the addition of different crystal phases of alumina
to slurries consisting of quartz and slaked lime for synthesis of Al‐substituted tobermorite. XRD results showed that Al‐substituted tobermorite formed after the reaction. It was clear that two kinds of Al‐substituted tobermorite synthesized using different alumina crystal phases shows different morphologies. The difference in the reactivity of the
had an influence in the hydrothermal reaction environment. The coordination number and chemical bonding‐state of Al caused the different morphology of the tobermorite.