The aggregation kinetics of precipitated silica particles is studied in a laboratory batch reactor. A method using destabilisation of a silica sol is developed to observe the aggregation process in absence of any other precipitation phenomena. The evolution of the moments of the particle size distribution (PSD) against time shows that the silica aggregation proceeds in two stages - a perikinetic aggregation stage, for particles smaller than 250 nm, whose kinetic rate depends on physico-chemical parameters, and a rapid orthokinetic aggregation stage, for larger particles. Once they have reached their maximal size, particles undergo breakage, whose rate depends on hydrodynamic conditions. Expressions for the evolution of the first moments (up to sixth order) against operating conditions are derived.