Effect of nano SiO₂ size on fresh properties of self-compacting concretes

Self-compacting concrete (SCC) is one of the most important developments in construction industry. SCC mix design has differences from conventional concrete mix design in order to obtain self-compacting ability. These mixtures necessitates the use of powerful superplasticizers, smaller maximum aggregate size, higher amount of fine materials, and lower water/binder ratio mixtures. Using high amount of fine materials causes a reduction in total coarse aggregate content. This reduction causes changes in elastic properties of hardened concrete. In this study, Nano SiO₂, which is a nano-technological material having enormous specific surface area, was used with the aim of reducing the total fine material amount in the mix design. Therefore, fly ash, which was used as fine material, was reduced gradually. The volumetric emptiness occurred by this reduction was filled with aggregates. Two different sizes of nano SiO₂ with the average particle diameters of 35 nm and 17 nm were used. Five different percentages of nano SiO₂ samples were selected as 0.5%, 1.0%, 1.5%, 2.0% and 2.5%. In order to understand the fresh properties T₅₀₀, slump flow diameter, V-funnel and sieve segregation tests were performed. The results of these test indicated that the use of nano SiO₂ would be an effective method in order to reduce the total fine material amount of SCC mixtures.