Table of Contents
Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive strength, bond strength, and abrasion resistance.
Why silica is added in cement?
Condensed silica fume is a very fine, amorphous, and reactive mineral admixture. It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.
Why is silica fume used?
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.
Is cement made of silica?
Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore.
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 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 the formula of cement?
Chemical Formulas of Cement Materials C CaO M MgO C 3 S 3CaO·SiO 2 = tricalcium silicate = alite C 2 S 2CaO·SiO 2 = dicalcium silicate = belite C 3 A 3CaO·Al 2 O 3 = tricalcium aluminate.
What are the advantages of using silica fume in concrete?
Advantages of Using Silica Fume High early compressive strength. High tensile flexural strength and modulus of elasticity. Very low permeability to chloride and water intrusion. Enhanced durability. Increased toughness. Increased abrasion resistance on decks, floors, overlays and marine structures.
What are the properties of silica fume?
Various properties of silica fume cocnrete, including slump, air-content, compressive strength, flexural strength, permeability, and permeable void volume were investigated, and the effect of the silica fume replacement ratio of cement is described.
What is the difference between fly ash and silica fume?
Silica Fume is typically much more reactive, particularly at early ages , because of its higher silicon dioxide content and because of its very small particle size. Disadvantages of Fly Ash: – High-carbon fly ash materials tend to use more water and darken the concrete as well.
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.
Why cement is called portland cement?
When first made and used in the early 19th century in England, it was termed portland cement because its hydration product resembled a building stone from the Isle of Portland off the British coast. The first patent for portland cement was obtained in 1824 by Joseph Aspdin, an English mason.
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.
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.
How do you make silica fume?
Silica fume is a by-product from the production of elemental silicon or alloys containing silicon in electric arc furnaces. At a temperature of approximately 2000°C the reduction of high-purity quartz to silicon produces silicon dioxide vapor, which oxidizes and condenses at low temperatures to produce silica fume.
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 cement raw materials?
The most important raw materials for making cement are limestone, clay, and marl. These are extracted from quarries by blasting or by ripping using heavy machinery.
How is cement made step by step?
There are four stages in the manufacture of portland cement: (1) crushing and grinding the raw materials, (2) blending the materials in the correct proportions, (3) burning the prepared mix in a kiln, and (4) grinding the burned product, known as “clinker,” together with some 5 percent of gypsum (to control the time of.
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.
What is the chemical formula of cement Class 11?
Cement has 50−60% calcium oxide, 2−3% magnesium oxide, 20−25% silicon oxide, 1−2% iron oxide, 5−10% aluminium oxide and 1−2% silicon oxide. -The powdered limestone and clay are mixed in a 3:1 ratio.
What is the size of cement?
What is the average particle size of cement? Explanation: Approximately 95% of cement particles are smaller than 45 microns and the average particle size is 15 microns.
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 disadvantage of silica?
Disadvantages of Silica Fume/Micro Silica In case the external temperature is high, it will lead to early dry shrinkage. Hence, it is more prone to cracks which may ultimately affect the overall strength. The construction with the silica fume concrete is difficult; as workability of silica fume concrete is poor.
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.
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.
