What is the effect of silica fume on concrete?
It has been reported that if a typical dosage of silica fume of 8-10% by weight of cement is added in concrete, then its effect is between 50,000 and 100,000 microspheres percent particle; that is, concrete mix will be denser and cohesive due to fine particles of silica fume (Tomas et al. 2012).
How the concrete properties change with the addition of silica fume?
Results indicated that the use of silica fume in concrete increased the compressive strength of concrete. Increase in water-binder ratio reduced the compressive strength of concrete irrespective of the use of silica fume. Silica fume had no noticeable effect on the splitting tensile strength of concrete.
Does silica fume increase workability of concrete?
Silica fume is known to improve the mechanical characteristics of concrete. It is observed that the optimum dose of silica fume is 5% (by weight), when used as part replacement of OPC. The silica fume inclusion increases the workability and strength of concrete considerably.
What is silica fume concrete?
Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. Concrete containing silica fume can have very high strength and can be very durable. Silica fume is available from suppliers of concrete admixtures and, when specified, is simply added during concrete production.
Why is silica used in concrete?
Silica fume is an excellent admixture for concrete as it leads to better engineering properties. It will reduce thermal cracking caused by the heat of cement hydration, improve durability to attack by sulphate and acidic waters, and increase strength.
What is the purpose of silica fume?
Silica fume, a by-product of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
How much does silica fume cost?
Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
Why is silica fume used in high strength concrete?
Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance. Silica fume also blocks the pores in the fresh concrete so water within the concrete is not allowed to come to the surface.
What are the advantages of using fly ash in concrete?
Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. Fly ash use is also cost effective. When fly ash is added to concrete, the amount of portland cement may be reduced. Benefits to Fresh Concrete.
How do you mix silica fume in concrete?
There are two ways to add silica fume: (1) Input aggregate, then put silica fume and cement dry mix, then add water and other additives. (2) Put coarse aggregate + 75% water + silica fume + 50% fine aggregate, stir for 15-30 seconds, then add cement + admixture + 50% fine aggregate + 25% water, stir until uniform.
Is silica fume toxic?
Repeated exposure can damage the eyes. * High exposure to Silica, Amorphous (Fume) can cause a flu-like illness with headache, fever, chills, aches, chest tightness and cough. * Repeated exposure to Silica, Amorphous (Fume) can cause lung damage (fibrosis).