Table of Contents
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 role of SiO2 in cement?
Abstract. Amorphous silica (a-SiO2) in fine-grained form possesses a high pozzolanic activity which makes it a valuable component of blended binders in concrete production. The origin of a-SiO2 applied in cement-based composites is very diverse. Coagulated silica is applied in dosages of 5 and 10 % by mass of cement.
Is silica added to concrete?
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 to concrete?
Pozzolanic reaction occurs between silica fume and the CH, producing additional CSH in many of the voids around hydrated cement particles. Because of the high surface area of silica fume particles affecting the mobility of water within concrete, segregation and bleeding of concrete are virtually eliminated.
What is the advantage of using silica fumes in manufacturing of concrete?
(b) It gives high tensile strength and flexural strength and modulus of elasticity. (c) It provides higher bond strength to concrete. Condensed silica fume has a very low permeability to chloride and water intrusion. Silica fume increases the durability of concrete.
What is cement formula?
4CaO·Al2O3·Fe2O3 = calcium alumino ferrite. C-S-H. Calcium silicate hydrate, a colloidal and mostly amorphous gel with a variable composition; this is the major hydration product of Portland cement, constituting approximately 70 percent of the paste, and is the phase providing most of the strength and binding.
What is the role of alumina in cement?
Alumina: Alumina is Aluminium oxide. Alumina imparts quick setting property to the cement. Clinkering temperature is lowered by the presence of the requisite quantity of alumina. Excess alumina weakens the cement.
What is the percentage of silica in 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 micro silica concrete?
Microsilica is a mineral admixture composed of very fine solid glassy spheres of silicon dioxide. Most microsilica particles are less than 1 micron (0.00004 inch) in diameter, generally 50 to 100 times finer than average cement or fly ash particles.
What is the percentage of silicon dioxide in pure cement?
Silica fume has been used as an addition to concrete up to 15% by weight of cement, although the normal proportion is 7 to 10%. With an addition of 15%, the potential exists for very strong, brittle concrete.
What are the disadvantages of high silica cement?
disadvantages of silica fume in concrete Silica fume concrete is too viscous and difficult to apply.it is not easy to wipe the surface. Silica fume requires a high amount of water and needs to be used with a superplasticizer. The price of silica fume is relatively high compared to cement and fly ash.
What is the difference between silica fume and microsilica?
Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide(SiO2). Concrete containing silica fume can have very high strength and can be very durable. Micro Silica Fume or Microsilica is finer particle than Cement. It is produced by some chemical processing of the ash.
Where can we get silica fume?
Silica fume is a byproduct in the carbothermic reduction of high-purity quartz with carbonaceous materials like coal, coke, wood-chips, in electric arc furnaces in the production of silicon and ferrosilicon alloys.
What is meant by pozzolanic material?
Pozzolanic materials are natural substances or industrial pozzolanas, siliceous or silico-aluminous, or a combination thereof. Although fly ash and silica fume have pozzolanic properties, they are specified in separate clauses.
What are the advantages of using fly ash in concrete?
Fly Ash has very small particles which makes the concrete highly dense and reduces the permeability of concrete. It can add greater strength to the building. The concrete mixture generates a very low heat of hydration which prevents thermal cracking. Fly Ash concrete is resistant to acid and sulphate attacks.
Is air entrained concrete stronger?
Air entrainment affects compressive strength of concrete and its workability. It increases the workability of concrete without much increase in water-cement ratio. When workability of concrete increases, its compressive strength decreases. Nov 14, 2013.
What are the types of cement?
Different Types Of Cement Ordinary Portland Cement (OPC) Portland Pozzolana Cement (PPC) Rapid Hardening Cement. Extra Rapid Hardening Cement. Low Heat Cement. Sulfates Resisting Cement. Quick Setting Cement. Blast Furnace Slag Cement.
What is the main component of cement?
As described in it, cement is a powdery substance made with calcined lime and clay as major ingredients. Clay used provides silica, alumina, and iron oxide, while calcined lime basically provides calcium oxide.1. Introduction. Compound Potassium oxide Formula K2O Notation K wt.% ≤2.
What is a natural cement?
: a hydraulic cement made from a naturally occurring limestone containing up to 25 percent argillaceous material — compare portland cement.
What is the role of Fe2O3 in cement?
It was founded that the optimal quantity of Fe2O3 is 0,01 % by weigth of cement in the presence of polymer powder PAV-22, because it increases the hardened cement stone flexural strength, and slightly decrease the compressive strenght.
Which ingredient gives Colour to the cement?
Iron oxide is present about 0.5 – 6.0 % in cement, which provides colour, hardness and strength to the cement.
Why is lime used in cement?
Lime provides high water retention that allows for maximum early curing of the cementitious materials. High initial flow which permits easy complete coverage of masonry units. The low air content of cement-lime mortar increases bond strength.
What is cement and its properties?
Three types of strength of cement are measured compressive, tensile and flexural. Various factors affect the strength such as water-cement ratio, cement-fine aggregate ratio, curing conditions, size and shape of a specimen, the manner of molding and mixing, loading conditions and age.
Who invented cement?
The invention of portland cement usually is attributed to Joseph Aspdin of Leeds, Yorkshire, England, who in 1824 took out a patent for a material that was produced from a synthetic mixture of limestone and clay.
What is C3S in cement?
It is the hydration of the calcium silicate, aluminate, and aluminoferrite minerals that causes the hardening, or setting, of cement. The ratio of C3S to C2S helps to determine how fast the cement will set, with faster setting occurring with higher C3S contents. Lower C3A content promotes resistance to sulfates.
