The synergistic effect of nano-silica with blast furnace slag in cement based materials

The synergistic effect of nano-silica (NS) and blast furnace slag (BFS) have been studied. A constant water-to-binder ratio (w/b) of 0.5 was used for all mortars. The different dosage (10%, 20%, 30% and 40%wt) of BFS and 3%wt NS were added into cement. The results indicated that comparing with the reference BFS mortars without silica inclusion, incorporation of a small amount of NS in cement containing BFS increased 28 days compressive strength, significantly. The incorporation of 3%wt NS in the cement pastes with 30%wt dosage of BFS have the highest compressive strength (59.42 MPa). In the work, the heat of hydration, non-evaporable water content and pozzolanic activity of BFS were studied, and the results showed that NS has a negative effect on the hydration of BFS; Through the analysis of the total porosity and the pore size distribution, NS and BFS can significantly reduce the porosity of the cement matrix, and increase the density, which is also an explanation of the phenomenon of increased compressive strength.