Fresh and rheological behavior of nano-silica and fly ash blended self-compacting concrete

• Nano-silica (NS) was utilized with different contents up to 6% in the production of self-compacting concrete (SCC).
• Fly ash (FA) was utilized with contents of 0%, 25%, 50%, and 75% by weight of total binder content.
• Combined effect of NS and FA on fresh properties and rheological behavior of SCC was experimentally investigated.
• Workability and rheology of SCC were significantly influenced by NS and FA.

The study herein addresses the effect of nano-silica (NS) and fly ash (FA) content on the fresh and rheological properties of self-compacting concrete (SCC). Four SCC series were designed with constant total binder content of 570 kg/m3 and at a water-to-binder (w/b) ratio of 0.33. Portland cement (PC) was substituted with NS with replacement levels of 0%, 2%, 4%, and 6% by weight in all SCC series. FA was not used in the production of first concrete series while in second, third, and fourth concrete series, FA was used at replacement levels of 25%, 50%, and 75% of total binder content by weight, respectively. Fresh properties of mixtures were experimentally investigated in terms of slump flow diameter, T50 slump flow time, V-funnel flow time, and L-box height ratio. Moreover, the rheological behavior of the SCCs was evaluated by applying the Herschel–Bulkley and modified Bingham models on the data obtained from the ICAR rheometer. Furthermore, a statistical analysis was applied to evaluate the significance of the experimental parameters such as NS and FA contents. The experimental results indicated that the incorporation of FA enhanced the fresh characteristics of the SCC mixtures while NS aggravated them.