Advance Construction Material – Micro Silica In Concrete

        Micro silica is an amorphous type of silica dust mostly collected in bag house filters as by-product of the silicon and ferro-silicon production. The paper summarizes important physical and chemical properties of micro silica and uses those results for an evaluation of micro silica from a Health Safety and Environment (HSE) standpoint. Micro silica consists of spherical particles with an average particle size of 150 nm and a specific surface area of typically 20 m3/g. The chemical and physical properties of this inorganic product are different as compared to other amorphous and crystalline silica poly morphs. More than 500.000 MT of micro silica are sold to the building industry world-wide and are used in fibre cement, concrete, oil-well drilling, refractories, and even in polymers.

        Micro silica contains trace amounts of heavy metal oxides and organic deposits, which originate from natural raw materials. Since the concentration of these impurities is very low, micro silica complies with company policies and international regulations. Traces of crystalline silica in micro silica do not seem to represent a health risk, neither for silicosis nor for lung cancer, due to the low levels and the large particle size. According to the International Agency for Research on Cancer (IARC), there is insufficient evidence for the carcinogenicity of silica fume, in contrast to crystalline silica. In order to assess potential health risks of micro silica and compliance with international regulations from an occupational hygienist’s point of view, one has to collect fragments of information from different analytical techniques. Putting these fragments together results in a cohesive picture. All evidences indicate that micro silica is not a hazardous product when applied as advised.

        When pozzolanic materials are incorporated to concrete, the silica present in these materials react with the calcium hydroxide released during the hydration of cement and forms additional calcium silicate hydrate (C – S – H ), which improve durability and the mechanical properties of concrete. High strength concrete refers to concrete that has a uniaxial compressive strength greater than the normal strength concrete obtained in a particular region. High strength and high performance concrete are being widely used throughout the world and to produce them, it is necessary to reduce the water binder ratio and increase the binder content. High strength concrete means good abrasion, impact and cavitations resistance. Using high strength concrete in structures today would result in economical advantages. In future, high range water reducing admixtures (Super plasticizer) will open up new possibilities for use of these materials as a part of cementing materials in concrete to produce very high strengths, as some of them are make finer than cement.