Effect of the SI to AL Ratio of Amorphous Nanoaluminosilicates on the Hydration Reaction of Portland Cement

This study explored the effect of amorphous nanoaluminosilicate, with controlled silicon to aluminum ratio, on the hydration of portland cement. The effect of these nanomaterials on the early hydration reaction of cement was evaluated using isothermal calorimetry. The xerogel samples of the nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) before and after exposure to simulated cement paste pore solution. The performance of these nanoaluminosilicates was compared against nanosilica and nanoboehmite. The results show that the nanoaluminosilicates affected principally the hydration of the calcium aluminate phase by removing sulfate from the pore solution. The same effect was reported in cement paste samples containing 10times more concentration of metakaolin. The effect was found to be strongly dependent on the particle size, which was ultimately affected by the silicon to aluminum ratio of the original nanoparticle. Beside sulfate, it was found that the nanoparticles also incorporate alkalis, calcium, and chloride from the pore solution to form calcium aluminosilicate hydrate and hydrated calcium aluminates (AFm) phases.