A Sadrmomtazi - Assistant Professor, Dept. of Civil Engg, Faculty of Engg, University of Guilan, Rasht, Iran
A Fasihi - M.S. Student, Dept. of Civil Engg, Faculty of Engg, University of Guilan, Rasht, Iran
F Balalaei - M.S., Fanavari Park of Guilan, Rasht, Iran
A.K Haghi - Professor, Dept. of Textile Engg, Faculty of Engg, University of Guilan, Rasht, Iran

It has been found that physical properties of concrete, particularly strength and permeability significantly depend on its pore structure. Ultra fine particles of nano- SiO2 fill the voids of CSH structure and provide more homogenous distribution of hydrated products. This effect of nano-SiO2 enhances the durability of cement composites as well as the strength. In this paper, influence of nano-SiO2 on different properties of cement mortar was investigated in comparison with silica fume (SF) as a well-known active pozzolan. Different amounts of nano-SiO2 (0, 1%, 3%, 5%, 7%and 9%) were incorporated into the ordinary cement mortar. Mechanical properties, shrinkage, water absorption of the specimens were determined. Results showed that the optimal content of Nano-SiO2 in plain cement mortar was around 7%. Nano-SiO2 particles were more effective in developing higher mechanical strength and lower water absorption than that of SF. Yet the mortar containing nano-SiO2 experienced higher shrinkage than that of SF mortar.

cement mortar, mechanical properties, nano-SiO2, silica fume,shrinkage