Nano-silica for concrete

Conventional concrete contains silica (SiO2) as part of the normal mix. Even high energy milling of ordinary portland cement (OPC) clinker and standard sand that produces a greater particle size diminution with respect to conventional OPC increases the compressive strength of the refined material 3 to 6 times higher. But particle packing in concrete can only be improved by using nano-silica which leads to a densification of the micro and nanostructure resulting in improved mechanical properties of the concrete.
Thus nano-silica addition to cement based materials controls the degradation of the fundamental C-S-H (calcium-silicate-hydrate) reaction of concrete caused by calcium leaching in water as well as blocks water penetration. This leads to improvements in durability and improved particle packing.
On the other hand addition of fly ash not only improves concrete durability, strength and, importantly for sustainability, reduces the requirement for cement, but, the curing process of concrete is slowed by the addition of fly ash and early stage strength is also low in comparison to normal concrete.
With the addition of SiO2 nanoparticles part of the cement is replaced but the density and strength of the fly-ash concrete improves particularly in the early stages. Haematite (Fe2O3) nanoparticles added to concrete increases strength as well as offering the benefit of monitoring stress levels through the measurement of section electrical resistance.