Table of Contents
How do you use silica fume in concrete?
(1) Put in aggregate, then put in silica fume, cement and dry mix, then add water and other additives. (2) Put in coarse aggregate + 75% water + silica fume + 50% fine aggregate, stir for 15-30 seconds, then put in cement + concrete admixture + 50% fine aggregate + 25% water, and stir until uniform.
What is concrete 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 does silica fume react in concrete?
Silica fume is typically used at replacement levels of 5–10% in high performance concrete to improve strength and durability. It not only can react with calcium hydroxide to produce C–S–H, but also modifies the microstructure of the cement paste due to its fine particle size.
Is code for silica fume for concrete?
3.0 For the purpose of this standard, the definitions given in IS 4305 and the following shall apply. 3.1 Silica Fume — Very fine pozzolanic material, composed mostly of amorphous silica produced by electric arc furnaces as a byproduct of the production of elemental silicon or ferro-silicon alloys.
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.
Is code for silica fume?
What is the specific gravity of silica?
2.2
Specific gravity is a relative number that tells how silica fume compares to water, which has a specific gravity of 1.0. Silica fume specific gravity is 2.2, which is somewhat lighter than portland cement, which has a specific gravity of 3.15.
What is the percentage of alumina in Portland cement?
The cement contains 35 to 40 percent lime, 40 to 50 percent alumina, up to 15 percent iron oxides, and preferably not more than about 6 percent silica.
What is the density of silica?
2.65 g/cm³Silicon dioxide / Density
How many types of silica are there?
The various forms of crystalline silica are: α-quartz, β-quartz, α-tridymite, β-tridymite, α-cristobalite, β-cristobalite, keatite, coesite, stishovite, and moganite (NIOSH, 2002).
What is the ratio of silica to alumina?
Investigations have been carried out on laboratory clinker made from cement raw meals with a lime saturation factor of 93%, and an alumina ratio of 2.0. The silica ratio (1.6–3.2), the alkali contents and the degree of sulfatisation were varied.
What is the ratio of silica to alumina required for a good quality cement?
between 2.5 to 4.0
For a good quality cement the ratio &silica (SiO2) and alumina (Al2O3) should be between 2.5 to 4.0.
Why silica is used in concrete?
Why silica is used in cement?
How much silica fume to add to concrete?
Setting time and strength development. When used at normal replacement rates,silica fume has little effect on setting time and little impact on heat of hydration.
What is the role of silica in concrete?
The three basic constituents of hydraulic cements are lime,Silica,alumina,and Iron oxide.
Does silica fume darken concrete?
The use and relative percentage of admixtures can also affect the color. For example, mineral admixtures such as silica fume can darken concrete. Pozzolans such as flyash and ground granulated blast furnace slag (GGBFS) also contribute to the color. Consistency in type, amount, and mixing results in color consistency.
How does microsilica improve concrete?
Silica Fume Waterproof Concrete