Table of Contents
Microsilica, also as silica fume or condensed silica fume, is a mineral admixture composed of very fine solid glassy spheres of silicon dioxide. As a result, microsilica concrete is able to strongly protect reinforcement and embedments from aggressive agents.
What is the purpose of micro silica in concrete?
Microsilica or silica fume is an excellent admixture for concrete as it leads to better engineering properties. It reduces thermal cracking, improves durability, and increases strength.
What is Micro Silica?
Microand nanosilica (μ/n-SiO2) Silica fume, also known as microsilica, is an amorphous polymorph of silicon dioxide, silica. It is a by-product of the carbothermic reduction of high purity quartz in electric arc furnaces in the production of silicon and ferrosilicon alloys.
Is micro silica waterproof?
4.4 Silica Fume Waterproof Concrete Because of its low permeability, micro-silica can be use as an integral water-proofer for below ground structures where some dampness is acceptable, eg Car parks.
What does silica cement mean?
: a refractory mortar suitable for laying silica brick.
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.
Which is a property of micro silica?
Properties of Microsilica Microsilica is a grey; nearly white to nearly black powder. Spherical particles less than 1mm in diameter. The bulk density of is based on the degree of densification and varies from 130 to 600 kg/m3.
What is the meaning of pozzolanic?
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement.
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 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 is the role of alumina in cement?
Alumina: It imparts quick setting property to the cement. It acts as a flux and lowers the clinkering temperature. Alumina in excess quantity reduces the setting time of cement but simultaneously reduces the strength of cement.
What is high performance concrete?
High-performance concrete (HPC) is concrete that has been designed to be more durable and, if necessary, stronger than conventional concrete. High-strength concrete is defined as having a specified compressive strength of 8000 psi (55 MPa) or greater.
Why is silica bad for you?
Breathing in very small (“respirable”) crystalline silica particles, causes multiple diseases, including silicosis, an incurable lung disease that leads to disability and death. Respirable crystalline silica also causes lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.
How much silica does it take to get silicosis?
Because silicosis is caused by cumulative or repeated exposure to respirable crystalline silica, it makes sense that we would want to limit exposure as much as possible! OSHA has set the Personal Exposure Limit (PEL) at 50 micrograms per cubic meter of air, averaged over an 8 hour shift.
What is silica good for?
Silica is an important trace mineral that provides strength and flexibility to the connective tissues of your body — cartilage, tendons, skin, bone, teeth, hair, and blood vessels. Silica is essential in the formation of collagen, the most abundant protein found in your body.
What are the advantages of silica fume in concrete?
Advantages of silica fume in concrete: It does not contain crystalline water, does not participate in the curing reaction, and does not affect the reaction mechanism. (2) good infiltration for various kinds of resin, good adsorption performance, easy to mix, no agglomeration phenomenon.
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.
Which of the following grades is not ordinary concrete?
Hence, M40 grade of concrete is not used as ordinary concrete.
Is silica a cement?
Many common construction materials contain silica including, for example, asphalt, brick, cement, concrete, drywall, grout, mortar, stone, sand, and tile.
Is silica fume expensive?
Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
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).
Which is 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.
Is pozzolana a cement?
Pozzolanic cements are mixtures of portland cement and a pozzolanic material that may be either natural or artificial. The natural pozzolanas are mainly materials of volcanic origin but include some diatomaceous earths. Artificial materials include fly ash, burned clays, and shales.
Can Pozzolans react without cement?
The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties.
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.
Is silica a silicon dioxide?
Silicon dioxide (SiO2), also known as silica, is a natural compound made of two of the earth’s most abundant materials: silicon (Si) and oxygen (O2). Silicon dioxide is most often recognized in the form of quartz. It makes up more than 95 percent of known rocks on the planet.
Is silica fume A admixture?
Silica fume is a mineral admixture, composed of submicron particles (100 to 150 times smaller than a grain of cement) of amorphous silicon dioxide.
What is silica fume and its uses?
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 do you mix 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.
Why is silica fume a good pozzolan?
Silica fume is a pozzolanic material composed of extremely fine, amorphous spheres produced as a byproduct in the manufacture of silicon metals. It has a high water demand and it is more reactive than natural pozzolan or fly ash. It increases the compressive strength significantly.
What is the purpose of micro silica in concrete?
Microsilica or silica fume is an excellent admixture for concrete as it leads to better engineering properties. It reduces thermal cracking, improves durability, and increases strength.
What is Micro Silica?
Microand nanosilica (μ/n-SiO2) Silica fume, also known as microsilica, is an amorphous polymorph of silicon dioxide, silica. It is a by-product of the carbothermic reduction of high purity quartz in electric arc furnaces in the production of silicon and ferrosilicon alloys.
Is micro silica waterproof?
4.4 Silica Fume Waterproof Concrete Because of its low permeability, micro-silica can be use as an integral water-proofer for below ground structures where some dampness is acceptable, eg Car parks.
What does silica cement mean?
: a refractory mortar suitable for laying silica brick.
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.
Which is a property of micro silica?
Properties of Microsilica Microsilica is a grey; nearly white to nearly black powder. Spherical particles less than 1mm in diameter. The bulk density of is based on the degree of densification and varies from 130 to 600 kg/m3.
What is the meaning of pozzolanic?
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement.
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 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 is the role of alumina in cement?
Alumina: It imparts quick setting property to the cement. It acts as a flux and lowers the clinkering temperature. Alumina in excess quantity reduces the setting time of cement but simultaneously reduces the strength of cement.
What is high performance concrete?
High-performance concrete (HPC) is concrete that has been designed to be more durable and, if necessary, stronger than conventional concrete. High-strength concrete is defined as having a specified compressive strength of 8000 psi (55 MPa) or greater.
Why is silica bad for you?
Breathing in very small (“respirable”) crystalline silica particles, causes multiple diseases, including silicosis, an incurable lung disease that leads to disability and death. Respirable crystalline silica also causes lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.
How much silica does it take to get silicosis?
Because silicosis is caused by cumulative or repeated exposure to respirable crystalline silica, it makes sense that we would want to limit exposure as much as possible! OSHA has set the Personal Exposure Limit (PEL) at 50 micrograms per cubic meter of air, averaged over an 8 hour shift.
What is silica good for?
Silica is an important trace mineral that provides strength and flexibility to the connective tissues of your body — cartilage, tendons, skin, bone, teeth, hair, and blood vessels. Silica is essential in the formation of collagen, the most abundant protein found in your body.
What are the advantages of silica fume in concrete?
Advantages of silica fume in concrete: It does not contain crystalline water, does not participate in the curing reaction, and does not affect the reaction mechanism. (2) good infiltration for various kinds of resin, good adsorption performance, easy to mix, no agglomeration phenomenon.
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.
Which of the following grades is not ordinary concrete?
Hence, M40 grade of concrete is not used as ordinary concrete.
Is silica a cement?
Many common construction materials contain silica including, for example, asphalt, brick, cement, concrete, drywall, grout, mortar, stone, sand, and tile.
Is silica fume expensive?
Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
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).
Which is 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.
Is pozzolana a cement?
Pozzolanic cements are mixtures of portland cement and a pozzolanic material that may be either natural or artificial. The natural pozzolanas are mainly materials of volcanic origin but include some diatomaceous earths. Artificial materials include fly ash, burned clays, and shales.
Can Pozzolans react without cement?
The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties.
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.
Is silica a silicon dioxide?
Silicon dioxide (SiO2), also known as silica, is a natural compound made of two of the earth’s most abundant materials: silicon (Si) and oxygen (O2). Silicon dioxide is most often recognized in the form of quartz. It makes up more than 95 percent of known rocks on the planet.
Is silica fume A admixture?
Silica fume is a mineral admixture, composed of submicron particles (100 to 150 times smaller than a grain of cement) of amorphous silicon dioxide.
