Dear Mohammad Ali thank you for your response. As I know the silica nanoparticles are spherical. But some shape as rod or solar shapes are now available with some synthesis methods for some application. But I mean is the best shape in addition of powder and coloids of silica that is suitable for concrete.
Dear Maryam, as i litrature for my research, i found all nano silica fume used in concrete spherical, by the way, i attached related papers which can help you.