Referring to the fresh concrete, silica fume reacts in two ways: a pozzolanic effect and a filler reaction. In the pozzolanic reaction, it is capable of reacting with the calcium hydroxide chemically to produce an subsdiarary amount of calcium silicate hydrate, which offers concrete with great resistance.There is an block of concrete pores and a abatement of permeability.
What's more, it still creats a filler effect,making the spaces created by the free water in the cement module and wraping the hollow steel bar materials in a better way, whose mechanical property is depending on extreme slender of material.
Another element should be included: the ecological issue. These additions are remains from the production of silicon metal and ferrosilicon alloys, in the case of silica fume, and silica from rice husk, which are left in the air and pollute the environment in a worst way.
As well as sticking to have better durability and stability of reinforced concrete structures, there is more and more research being done considering the standardization of tests to analyse such parameters. Some international standards already recognize some objects, but in Brazil there is still much to be done in this area.
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