Microsilica (Silica fume)

Silica particles are about 30 to 100 times smaller than cement grains and consist almost entirely of amorphous silicon dioxide (SiO₂).

They fill a part of the pore space (micro-filling effect) and support the increase in strength through a pozzolanic secondary reaction.

In addition, the corrosion protection for the reinforcement or the resistance against water penetration can be improved.

It is also used in the fields of refractories, granulated fertilizers (coating) and in the production of plastics and adhesives.

PCC BakkiSilicon hf. has been designed as one of the most climate-friendly and environmentally compatible silicon metal plants in the world. The use of Iceland´s geothermal resources in the silicon metal production cuts greenhouse gas emissions by around two-thirds as compared to other plants around the world. With silicon metal production at the PCC plant powered entirely by renewable energy, the overall CO₂ footprint of the whole process is drastically reduced.

Silica dust - so-called micro-silica, which is a by-product of the production of metallic silicon and ferrosilicon alloys in arc furnaces. Microsilica consists of extremely fine dust particles, which can be assumed to be on average 100 times smaller than the average size of a cement grain. For technical reasons, silica dust is delivered in a concentrated form as micro granules which are agglomerates of individual particles.

Microsilica is a very important addition to tight concrete. Replacing 15% of cement with micro-silica increases the tightness of concrete several dozen times, which is difficult to achieve by other methods. In addition, the compression strength is increased by 20% and absorbability is reduced three times. However, the addition of microsilica is associated with a decrease in consistency, which makes the fresh concrete mix difficult to work with. This can be prevented by adding a superplasticizer. It is worth noting, however, that the superplasticizer cannot be used uncritically, especially in micro-silica concretes, due to its negative impact on strength.