Identification of solvated species present in concentrated and dilute sodium silicate solutions by combined 29Si NMR and SAXS studies

► High siliceous species solubility observed in Na silicate solution in basic medium (pH = 11.56) results from the formation of a Si7O18H4Na4 neutral complex. ► Si7O18H4Na4 species are gathered into aggregates in the intial solution. ► Charged species are formed by dilution due to the dissociation of neutral species. ► Dilution leads to increase colloids size by polycondensation reaction and to decrease the size of aggregates.