Solubility and characterization of synthesized 11 Å Al-tobermorite

The structure and solubility of hydrothermally prepared 11 Å Al-tobermorite with Al/(Al + Si) = 0.1 has been studied. NMR and FTIR data indicated the formation of a cross-linked, well crystalline 11 Å Al-tobermorite and preferential uptake of Al in the branching sites of the silicate chains. The incorporation of Al in branching sites of 11 Å tobermorite increased the basal spacing of the 11 Å Al-tobermorite by ~0.18 Å. Solubility experiments indicated little effect of temperature on the solubility of 11 Å Al-tobermorite and a weak stabilization of 11 Å Al-tobermorite with regard to 11 Å tobermorite. The experimental data confirmed the strong similarity in structure, Al-uptake, and solubility with poorly ordered C-A-S-H gel, although C-A-S-H gels showed a lower degree of ordering, the absence of cross-linking, an increased basal spacing, and a higher solubility.