In this study, colloidal nano SiO2 (CNS), which can be assumed as a multi-functional nano-technological material in cement-based systems, was utilized in an effort to reduce the total fine material content in self-compacting concrete (SCC) designs. The influence of CNS addition on flow properties and rheological parameters has been investigated. Three different average particle diameter of CNS which was used to modify the SCC mixtures are 35 nm, 17 nm and 5 nm. CNSs were used at different amounts and total fly ash amount in the mix design was decreased step by step from 1601 kg/m(3) down to 0 kg/m(3). The volumetric emptiness occurred by the reduction of fine materials was filled by aggregates. On fresh state, T-500 slump flow time, slump flow diameter, V-funnel time, static penetration resistance, sieve segregation and visual stability index tests were performed. Moreover, rheological parameters such as static yield stress, dynamic yield stress and plastic viscosity were obtained by using a concrete rheometer. In this way, it was aimed to design SCC mixtures with reduced fine material content by benefiting of the viscosity modifying effect of CNSs with various sizes. Results have shown that the effectiveness of CNS, in an effort to reduce the fine material content in SCC design is very significant. (C) 2017 Elsevier Ltd. All rights reserved.