Controlling the properties of precipitated silica (PS) synthesized by acidizing sodium silicate solution is a significant challenge. Here, we report the effect of gelation on the BET surface area and pore volume of the PS produced at the pilot scale. H2SO4 was added to a mixture of sodium silicate and sodium chloride in two stages: the first stage ends before the gelation point and the second one ends as pH of solution reached to 5. The interval (Delta t) from the end of the first stage to the gelation point was recorded to evaluate its effect on the properties of the resulting PS. The obtained samples were characterized by nitrogen adsorption-desorption method, field emission scanning electron microscopy (FE-SEM), and field emission scanning transmission electron microscopy (FE-STEM). The results revealed that the BET surface area and pore volume of the prepared PS decreases with the increase of Delta t and temperature, while the pore size is not affected. The variations in the properties of the PS were successfully explained by the application of a percolation model to the flocculation and bridging of the primary particles. (C) 2012 Elsevier B.V. All rights reserved.