Nano silica (also named as nano-silicon dioxide) is a kind of inorganic chemical material, commonly known as white carbon black. Because of its ultra-fine nano scale and its size range of 1-100nm, it has many unique properties, such as optical properties against ultraviolet, which can improve other materials’ anti-aging, strength and chemical resistance. A very wide range of uses. Nanoscale silica is amorphous white powder. It is non-toxic, tasteless and pollution-free. Its microstructure is spherical, with a flocculated and netlike quasi granular structure. Its molecular formula and structural formula are SiO2, and it is insoluble in water.
Nano silica Physical property:
The appearance of nano silica is an amorphous white powder. The size range of the particles is 1-100 nanometers, the microstructures are spherical, and the particles are floc and reticulate quasi granular structure.
Dissolving properties: can not dissolve in water and acid (except hydrofluoric acid) and organic solvents, and can be dissolved in alkali and hydrofluoric acid.
The use of nano silica is very widely used, the weight is 0.5 – 2%, and the individual product system can reach more than 10%. The key to the performance of the product is that it is fully dispersed into the system. According to different systems, silica nanoparticles are dispersed in water, acetone, alcohols or other solvents according to different systems. For oil-based systems, auxiliaries can be supplemented for pretreatment.
Concrete is the most common used material for construction and their design consumes almost the total cement production in the world. The use of large quantities of cement produces increasing CO2 emissions, and as a consequence the green house effect. A method to reduce the cement content in concrete mixes is the use of silica fines. One of the silica fines with high potential as cement replacement and as concrete additive is nano-silica. However, the commercial Nano silica is synthesized in a rather complex way, resulting in high purity and complex processes that make them non-feasible for the construction industry. Furthermore, the application of Nano silica and its effect in concrete is not fully understood yet.
Nano silica in concrete:
Nano silica (equivalent to VK-SP30) can significantly improve the transition interface structure of aggregate and paste in concrete, and prove the influence of nano silica (equivalent VK-SP30) on the properties of concrete from microcosmic angle. Air entraining agent can improve the concrete slump but it can slightly decrease the expansion degree; can reduce the compressive strength of concrete at each stage; can significantly reduce the self shrinkage strain of concrete; improve the concrete anti permeability and frost resistance of Cl-, especially the frost resistance and durability. Although the retarder can reduce the early compressive strength of concrete, it has little effect on the later strength of concrete.
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