Micro Silica in Concrete–The Special Concrete

Abstract

The paper summarizes important physical and chemical properties of micro silica for an evaluation of micro silica from an Environment Health and Safety (EHS) point of view. Silica fume is an ultrafine material with spherical particles less than 1 μm in diameter, the average being about 0.15 μm. This makes it approximately 100 times smaller than the average cement particle. The bulk density of silica fume depends on the degree of densification in the silo and varies from 130 to 600 kg/m3. The specific gravity of silica fume is generally in the range of 2.2 to 2.3 Around 500.000 MT of micro silica are sold to the construction industry world-wide and are used in fiber cement, concrete, oil-well drilling and even in polymers. Micro silica contains trace amounts of heavy metal oxides and organic deposits, which originate from natural raw materials. But Evidences indicate that micro silica is not a hazardous product when used in construction. The advantages of using micro silica can be considerable as it reduces thermal cracking caused by the heat of cement hydration and can improve durability to attack by sulphate and acidic waters.