Nano-silica production by a sustainable process; application in building materials.

Concrete is the most widely produced manmade material. Current micro-silica is only applied in special cases, due to its high price, and nano-silica is not used in common practice yet. The neutralization of waste acids (either sulphuric or hydrochloric) with olivine produces tailored nano-silica [1][2]. The main factors that determine the rate of dissolution of olivine in acids at elevated temperatures are the olivine specific surface area, the temperature and the pH. The production parameters with a strong influence on the properties of the silica are the olivine composition and fineness, acid purity and concentration, temperature, releases of silica monomers rate and stirring speed. Nano-silica obtained by this process can be produced in large quantities, for low prices and by sustainable method so that mass application in concrete is within reach. It may replace cement in the mix, which is the most costly and environmentally unfriendly component in concrete. The use of nano-silica reduces the CO2 footprint of the manufactured concrete products and improves the properties in hardened state. Thus a concrete with better performance, lower costs and environmentally sustainable is designed. The application of these concretes can be anywhere, both in infrastructure and in buildings.