Time-Resolved SAXS Investigation of Correlation-Collapse in Self-Assembled Silica Microgranules during Pozzolanic Gelling

Abstract

The dynamics of phase evolution during reactive dissolution of the host matrix is of immense interest in the cementation process. We have investigated temporal evolution of structural correlation during hydration-driven gelling across nanoporous spray-dried silica microgranules. Time-resolved small-angle X-ray scattering (SAXS) experiments provide the pathway of the pozzolanic gelling that extends over nearly one month. The individuality of the nanoparticles gets completely wiped out within a month owing to gelling. The choice of the novel correlated nanostructured silica granules as pozzolans allows unique advantages owing to the special attributes in the scattering profile. SAXS clearly indicated the competitive process arising due to formation and growth of gel at the expense of dissolving nanosilica. The ramified gel evolves nonlinearly and follows two-stage sigmoidal dependence. The scaling ansatz breaks down owing to geometrical constraints. Space-filling-based Monte Carlo simulation fairly corroborates the experimental observations. We believe that the present results will be useful for cement and concrete industries in particular and understanding the kinetics of new phase formation in general. Further, it will provide a novel way to use correlated nanostructured microspheres for control of the cementation process during setting of construction materials.