Limestone Detailed Solution. The correct answer is Limestone. Limestone is the main ingredient of cement.
- 1 What is the formula for cement?
- 2 What is the 4 main ingredient that make up concrete?
- 2.1 Is gypsum used to make cement?
- 2.2 What are the ingredients of concrete Mcq?
- 2.3 What are the 3 components of cement?
- 2.4 Why Portland is used in cement?
- 2.5 Why is cement a mixture?
- 3 What are uses of cement?
- 4 Why fly ash is used in cement?
- 5 What are the three 3 ingredients of concrete?
- 6 What is cement glue made of?
Which is the main ingredient in cement?
Visit ShapedbyConcrete.com to learn more about how cement and concrete shape the world around us. Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden.
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.
These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement. Bricklayer Joseph Aspdin of Leeds, England first made portland cement early in the 19th century by burning powdered limestone and clay in his kitchen stove.
- With this crude method, he laid the foundation for an industry that annually processes literally mountains of limestone, clay, cement rock, and other materials into a powder so fine it will pass through a sieve capable of holding water.
- Cement plant laboratories check each step in the manufacture of portland cement by frequent chemical and physical tests.
The labs also analyze and test the finished product to ensure that it complies with all industry specifications. The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials.
- After quarrying the rock is crushed.
- This involves several stages.
- The first crushing reduces the rock to a maximum size of about 6 inches.
- The rock then goes to secondary crushers or hammer mills for reduction to about 3 inches or smaller.
- The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln.
The cement kiln heats all the ingredients to about 2,700 degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special firebrick. Kilns are frequently as much as 12 feet in diameter—large enough to accommodate an automobile and longer in many instances than the height of a 40-story building.
The large kilns are mounted with the axis inclined slightly from the horizontal. The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.
As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles. Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers.
The heated air from the coolers is returned to the kilns, a process that saves fuel and increases burning efficiency. After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. Cement is so fine that 1 pound of cement contains 150 billion grains. The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects.
Although the dry process is the most modern and popular way to manufacture cement, some kilns in the United States use a wet process. The two processes are essentially alike except in the wet process, the raw materials are ground with water before being fed into the kiln.
Which of the following is the main ingredient of cement Bpsc?
Detailed Solution The correct option is Limestone. EXPLANATION: A limestone is a form of calcium carbonate which is used extensively for the manufacture of cement.
What are the main ingredients of Portland cement?
2 Cementitious materials – Portland cement (OPC) consists of tri and dicalcium silicates, tricalcium aluminate, and tetracalcium alumino ferrite and calcium sulfate as gypsum. It has adhesive and cohesive properties and is capable of binding together mineral fragments in presence of water so as to produce a continuous compact mass of masonary. Fig.2.1, Manufacturing process of Portland cement. Blended cements are mixtures of Portland cement and other hydraulic or non hydraulic materials (industrial and agricultural wastes such as fly ash, metakaoline, blast furnace slag, rice husk ash, etc.). Paste, mortar and Concretes are shown in Fig.2.2, Fig.2.2, Representation of OPC paste, mortar and concrete. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780128178546000027
What is the formula for cement?
Chemical Formulas of Cement Materials
|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 is the 4 main ingredient that make up concrete?
Essential Ingredients For A Concrete Mixture Concrete is and has been for thousands of years, a very popular building material. Made up of just a few basic ingredients, concrete is the most widely used man-made material on the planet. Humans use more concrete than all other building materials combined.
So what is concrete exactly? Concrete is a mixture of cement, air, water, sand, and gravel–it’s as simple as that! Not exactly. The typical concrete mix is made up of roughly 10% cement, 20% air and water, 30% sand, and 40% gravel. This is called the 10-20-30-40 Rule–though proportions may vary depending on the type of cement and other factors.
Now let’s discuss each ingredient and the important role they play in your mix.
Is gypsum used to make cement?
(2) The Mixing Amount of Gypsum – Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat.
The major reason is that C 3 A in the clinker can dissolve in water quickly to generate a kind of calcium aluminate hydrate, a coagulant agent, which will destroy the normal use of cement, the retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C 3 A quickly to generate calcium sulfoaluminate hydrate (ettringite) which deposits and forms a protection film on the cement particles to hinder the hydration of C 3 A and delay the setting time of cement.
If the content of gypsum is too little, the retardation affect will be unobvious. Too much gypsum will accelerate the setting of cement because gypsum can generate a coagulating agent itself. The appropriate amount of gypsum depends on the content of C 3 A in the cement and that of SO 3 in gypsum, and it also related to the fineness of cement and the content of SO 3 in clinker.
- The amount of gypsum should account for 3% ~ 5% of the cement’s mass.
- If the content of gypsum exceeds the limit, it will lower the strength of cement and it can even lead to poor dimensional stability, which will cause the expanded destruction of cement paste.
- Thus, the national standard requires that the content of SO 3 should not be more than 3.5%.
Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845699550500049
What are the ingredients of concrete Mcq?
Here are 1000 MCQs on Concrete Technology (Chapterwise).1. What is Concrete Technology? a) Concrete Technology deals with the study of bricks b) Concrete Technology is the study of building materials c) Concrete Technology deals with the study of properties of concrete d) None of the mentioned View Answer Answer: c Explanation: Concrete Technology is concerned with the study of concrete characteristics and their practical applications.
- Concrete is most often utilized as the foundation for most projects in the construction sector.2.
- What is concrete? a) A mixture of homogenous materials b) A mixture of material and hydrogen c) A mixture of cement and hydrogen sulphide d) A mixture of cement, water, and aggregates View Answer Answer: d Explanation: Concrete is a hardening building material made up of cement, fine aggregates (sand), and coarse aggregates combined with water.
It is a significant building material that is utilized widely in the construction of buildings, bridges, highways, and dams.3. Why concrete technology is needed? a) Concrete technology is needed to build a building b) Concrete technology is needed to address properties of concrete c) Concrete technology is needed to produce building materials d) None of the mentioned View Answer Answer: b Explanation: Concrete technology covers all elements of concrete, from mix design to batching, mixing, transporting, putting, consolidating, finishing, and curing, and gives guidance on all aspects of concrete from mix design to batching, mixing, transporting, placing, consolidating, finishing, and curing.4.
Concrete technology is useful for civil engineers because it allows them to _ a) know how to appropriately stock the materials needed for concrete b) conduct various concrete tests c) familiarise them with the fundamental principles of concrete d) all of the mentioned View Answer Answer: d Explanation: Concrete technology in civil engineering helps to know how to appropriately stock the materials needed for concrete, conduct various concrete tests and familiarise them with the fundamental principles of concrete.5.
Who is the father of concrete technology? a) William Aspdin b) Royston Saint John c) Joseph Aspdin d) None of the above View Answer Answer: a Explanation: William Aspdin (September 23, 1815 – April 11, 1864), a pioneer of the Portland cement industry, was an English cement maker. 7. How many basic types of concrete are there? a) 20 types b) 24 types c) 22 types d) 21 types View Answer Answer: b Explanation: Depending on the kind of construction, there are typically twenty-four distinct types of concrete used in the building and construction business.8.
- What is the full form of HRM in concrete technology? a) Human Resource Management b) Human Reserve Management c) Humidity and Resource Management d) None of the above View Answer Answer: a Explanation: In concrete technology, HRM is abbreviated as Human Resource Management.9.
- What are the ingredients of concrete? a) Binding material b) Fine aggregate c) Admixtures d) All of the above View Answer Answer: a Explanation: The binding material binds fine and coarse aggregate.
Fine aggregates fill the space in the coarse aggregate. Admixtures affect the setting time of cement.10. What is the objective of concrete technology? a) To find the material strength b) Calculate the amount of cement required c) To define and understand concepts related to Cement d) To define and understand concepts related to Concrete technology View Answer Answer: d Explanation: To identify and comprehend ideas connected to concrete technology, which includes the various types and properties of concrete as well as various adhesive materials and their critical application in the construction of safe and cost-effective structures.11.
- For a compressive strength of 3000 psi, the lightweight cement content is _ pounds per cubic yard.
- A) 400-590 b) 440-560 c) 430-560 d) 730-750 View Answer Answer: b Explanation: Compressive strengths of 3000 psi requires 440-560 pounds per cubic yard, while compressive strengths of 2500 psi requires 400-510 pounds per cubic yard.12.
What is the importance of the Standard Consistency Test? a) It is used to determine the quality of water b) It is used to determine the quality of aggregates c) It is used to determine the quality of cement d) None of the above View Answer Answer: a Explanation: This test is used to assess how much water is needed to make a standard or typical consistency cement paste.
This test also helps to determine soundness, compressive strengths and setting time of the cement.13. Hydration of cement is chemical reaction of cement with _ a) base b) acid c) salt and acid d) water View Answer Answer: d Explanation: As water comes into contact with cement particles, hydration reactions immediately starts at the surface of the particles.
It is an exothermic reaction i.e., heat is released during the process. The resultant product of this reaction is hardened cement.14. Which of the following cement is used in sewage and water treatment plants? a) Sulphate Resisting Cement b) Quick Setting Cement c) Low Heat Cement d) Rapid Hardening Cement View Answer Answer: a Explanation: Sulphate resistance is excellent in cement with composition.
- This type of cement is utilized in the construction of foundations on soils with high sulphate levels in the subsoil.15.
- Which of the following cement is used for interior and exterior decorative works? a) Low Heat Cement b) High Alumina Cement c) Rapid Hardening Cement d) Colored Cement View Answer Answer: d Explanation: Colored cement is made by mixing 5-10% mineral pigments into Portland cement during the grinding process.
The color added to the cement can fade but the cement retains its workability and durability.16. Which of the following ratio is also known as water-cement ratio? a) Weight of water to the weight of aggregates b) Density of cement to the Density of cement c) Weight of water to the weight of cement d) Volume of cement to the volume of cement View Answer Answer: c Explanation: The water–cement ratio is the weight of water in a concrete mix divided by the weight of cement.
- The strength of concrete is proportional to the Cement water ratio and inversely proportional to the w/c ratio.17.
- How many layers of concrete are needed to fill a slump cone? a) 5 layers by volume b) 3 equal layers by height c) 3 equal layers by volume d) 5 layers View Answer Answer: c Explanation: 3 equal layers by volume are placed.
Fill the mold to a height of 12 inches in the shape of a frustum of a cone with a bottom diameter of 8 inches and a top diameter of 4 inches. Then, instead of filling it in three equal levels by height, fill it in three equal layers by volume.18. What is the total percentage of aggregates in concrete in terms of volume? a) 65-80% b) 90% c) 60-75% d) 40% View Answer Answer: c Explanation: Aggregates are split into two groups, accounting for 60-75 percent of the total volume of concrete.
Gravels, crushed stone, Natural gravel, and sand, etc. are the aggregates of the concrete.19. Crushed stone, gravel, and ordinary sand are examples of which type of cement aggregate? a) Heavy-weight aggregate b) Lightweight aggregate c) Normal-weight aggregate d) Both Normal-weight and Heavy-weight aggregate View Answer Answer: c Explanation: Normal weight aggregates include crushed stone, gravel, and regular sand.
They’re widely utilized in the production of regular and asphalt concrete, and highway sub-base.20. What is the relation between the Coefficient of thermal expansion of concrete and the coefficient of thermal expansion in aggregates? a) Equal b) More than c) Inversely proportional d) Directly proportional View Answer Answer: d Explanation: The coefficient of thermal expansion refers to either expansion or contraction of a material with temperature.
- The coefficient of thermal expansion rises in tandem with aggregates’ coefficient of thermal expansion, and vice versa.21.
- What happens if mineral oil is present in mixing for concrete? a) Gives more slump b) Improves strength c) Gives a smooth surface d) Reduces strength View Answer Answer: b Explanation: Mineral oil, when used in mixing, enhances the strength of the by up to 2%.22.
What is wet process? a) Grinding and mixing of the raw materials in their overheated state b) Grinding and mixing of the raw materials in their wet state c) Grinding and mixing of the raw materials in their dry state d) Grinding and mixing of the raw materials in their medium state View Answer Answer: b Explanation: Wet process refers to the grinding and mixing of raw materials in their wet condition, while dry process refers to the grinding and mixing of raw materials in their dry form.23.
Which of the following increases the workability of concrete? a) Decreasing size of aggregates b) Increasing flaky aggregates c) Increasing size of aggregates d) Increasing fine aggregates View Answer Answer: c Explanation: Workability should be obtained by the use of a well-graded aggregate that has the largest maximum particle size possible.
Along with aggregate admixtures and air entrainment also increases the workability.24. The form work is usually removed after _ for walls, columns, and the vertical faces of all structural components. a) 24 to 48 hours b) 72 hours c) 56 hours d) 24 hours View Answer Answer: a Explanation: In all circumstances, 3/7 of the aforesaid period will suffice for rapid hardening cement, with the exception of vertical sides of slabs, beams, and columns, which should be held for 24 hours.25.
How is Creep related to the strength of concrete? a) Directly proportional b) Inversely proportional c) Equal d) Similar View Answer Answer: b Explanation: Creep increases as the cement ratio rises. In other words, it’s possible to say that creep is inversely related to concrete strength.26. What is equivalent flexural strength? a) The load value, which represents the average load-carrying capacity in the post-peak region up to a deflection of L/n b) The value of mean equivalent flexural strength adjusted to mean flexural strength c) The stress is derived when the peak load value is included in the rupture modulus equation d) The stress value produced when Pe,n is utilized in the equation of modulus of rupture to represent the average flexural strength in the post-peak zone up to a specific deflection of L/n View Answer Answer: d Explanation: Equivalent flexural strength is the stress value that represents the average flexural strength in the post-peak zone up to a certain deflection of L/n obtained when Pe,n is employed in the equation of modulus of rupture.27.
Which of the following stress can Plain cement concrete endure? a) Shear stress b) Tensile stress c) Compressive stress d) Tensile, compressive, and shear stresses View Answer Answer: c Explanation: Plain cement concrete is strong in taking compressive stress but weak in tensile stress.
It consists of water, cement, coarse aggregate, and fine aggregate.28. Which of the following is a discontinuity that occurs during the casting of molten metal and is caused by splashing, surging, or interrupted pouring? a) Flaking b) Blow hole c) Cold shut d) Burst View Answer Answer: c Explanation: Cold shut refers to a discontinuity in molten metal casting that can be generated by splashing, surging, halted pouring, or the meeting of two streams of metal coming from separate directions.29.
Which of the following property of a substance that resists abrasion or scratching that causes penetration or indentation? a) Hardness b) Stiffness c) Toughness d) Strength View Answer Answer: a Explanation: Hardness is the property of a material that resists penetration or indentation by abrasion or scratching.30.
Which of the following region absorbs less radiation and transmits more during radiography test for concrete? a) Low density region b) Low and high density regions adsorb c) High density region d) Low and high density regions absorb and transmit same amount of radiation View Answer Answer: a Explanation: In radiography test internal flaws are detected using short wavelength electromagnetic radiations such as X-rays and rays.
The component to be tested is put in the direction of radiations generated by X-rays or rays in this approach.31. Which of the following is not a type of Non-destructive testing? a) Ultrasonic test b) Eddy current testing c) Compression testing d) Visual testing View Answer Answer: a Explanation: Destructive testing, such as compression testing, is a sort of destructive testing.
This test is performed to assess how metals react when compressed. Non-destructive testing includes methods such as visual inspection, ultrasonic inspection, and eddy current testing.32. For a compressive strength of 4000 psi, the light weight cement content is _ pounds per cubic yard. a) 630-750 b) 440-560 c) 740-840 d) 530-660 View Answer Answer: d Explanation: The lightweight cement content for compressive strengths is 4000 psi is 530-660 pounds per cubic yard, whereas compressive strengths of 2500 psi are 400-510 pounds per cubic yard.33.
What happens when chalk is used? a) Crushed raw materials are put into a grinding mill, where they are dried and reduced to a fine powder b) It must be sieved and fed into a rotating dish known as a granulator c) It must be finely broken up and dispersed in water in a wash mill d) It must be blasted, then crushed, usually in two smaller crushers View Answer Answer: c Explanation: Chalk is finely broken up and disseminated in water in a wash mill when it is utilized.
In a similar manner, the clay is broken up and combined with water, usually in a wash mill.34. High strength concrete is defined purely on the basis of _ a) Tensile strength b) Compressive strength c) Good Aggregrates d) Poor Aggregrates View Answer Answer: b Explanation: High strength concrete is defined purely on the basis of its compressive strengths.35.
Which of the following is used to test the Standard consistency of cement? a) Duff Abrams apparatus b) Soundness meter c) Vicat apparatus d) Le Chatalier apparatus View Answer Answer: c Explanation: The standard consistency of a cement paste is described as that which allows the vicat’s plunger to penetrate to a depth of 5 to 7mm from the vicat mould’s bottom.36.
What are the 3 components of cement?
Composition of cement Composition of cement Introduction Portland cement gets its strength from chemical reactions between the cement and water. The process is known as, This is a complex process that is best understood by first understanding the chemical composition of cement. Manufacture of cement Portland cement is manufactured by crushing, milling and proportioning the following materials:
Lime or calcium oxide, CaO: from limestone, chalk, shells, shale or calcareous rock Silica, SiO 2 : from sand, old bottles, clay or argillaceous rock Alumina, Al 2 O 3 : from bauxite, recycled aluminum, clay Iron, Fe 2 O 3 : from from clay, iron ore, scrap iron and fly ash Gypsum, CaSO 4,2H 2 0: found together with limestone
The materials, without the gypsum, are proportioned to produce a mixture with the desired chemical composition and then ground and blended by one of two processes – dry process or wet process. The materials are then fed through a kiln at 2,600º F to produce grayish-black pellets known as clinker.
Chemical shorthand Because of the complex chemical nature of cement, a shorthand form is used to denote the chemical compounds. The shorthand for the basic compounds is:
|Calcium oxide (lime)||Ca0||C|
|Silicon dioxide (silica)||SiO 2||S|
|Aluminum oxide (alumina)||Al 2 O 3||A|
|Iron oxide||Fe 2 O 3||F|
|Water||H 2 O||H|
Chemical composition of clinker The cement clinker formed has the following typical composition:
|Compound||Formula||Shorthand form||% by weight 1|
|Tricalcium aluminate||Ca 3 Al 2 O 6||C 3 A||10|
|Tetracalcium aluminoferrite||Ca 4 Al 2 Fe 2 O 10||C 4 AF||8|
|Belite or dicalcium silicate||Ca 2 SiO 5||C 2 S||20|
|Alite or tricalcium silicate||Ca 3 SiO 4||C 3 S||55|
|Sodium oxide||Na 2 O||N||) )Up to 2|
|Potassium oxide||K 2 O||K|
|Gypsum||CaSO 4,2H 2 O||C S H 2||5|
Representative weights only. Actual weight varies with type of cement. Source: Mindess & Young Properties of cement compounds These compounds contribute to the properties of cement in different ways Tricalcium aluminate, C 3 A:- It liberates a lot of heat during the early stages of hydration, but has little strength contribution.
- Gypsum slows down the hydration rate of C 3 A.
- Cement low in C 3 A is sulfate resistant.
- Tricalcium silicate, C 3 S:- This compound hydrates and hardens rapidly.
- It is largely responsible for portland cement’s initial set and early strength gain.
- Dicalcium silicate, C 2 S: C 2 S hydrates and hardens slowly.
It is largely responsible for strength gain after one week. Ferrite, C 4 AF: This is a fluxing agent which reduces the melting temperature of the raw materials in the kiln (from 3,000 o F to 2,600 o F). It hydrates rapidly, but does not contribute much to strength of the cement paste.
- By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments.
- References: Sidney Mindess & J.
- Francis Young (1981): Concrete, Prentice-Hall, Inc., Englewood Cliffs, NJ, pp.671.
- Steve Kosmatka & William Panarese (1988): Design and Control of Concrete Mixes, Portland Cement Association, Skokie, Ill.
pp.205. Michael Mamlouk & John Zaniewski (1999): Materials for Civil and Construction Engineers, Addison Wesley Longman, Inc., : Composition of cement
Which of the following is not ingredients of cement?
Cement consist of essential compounds like lime or calcium oxide(CaO), Alumina or aluminium oxide(Al2O3) and Magnesia or Magnesium oxide(MgO). Na2O is not an important constituent of cement.
Where is cement made?
China produces the most cement globally by a large margin, at an estimated 2.5 billion metric tons in 2021. China’s cement production share equates to over half of the world’s cement. India was the world’s second-largest cement producer, with production amounting to a distant 330 million metric tons in 2021.
Why Portland is used in cement?
ASTM C150 – Five types of portland cements exist, with variations of the first three according to ASTM C150. Type I portland cement is known as common or general-purpose cement. It is generally assumed unless another type is specified. It is commonly used for general construction, especially when making precast, and precast-prestressed concrete that is not to be in contact with soils or ground water.
- The typical compound compositions of this type are: 55% (C 3 S), 19% (C 2 S), 10% (C 3 A), 7% (C 4 AF), 2.8% MgO, 2.9% (SO 3 ), 1.0% ignition loss, and 1.0% free CaO (utilizing Cement chemist notation ).
- A limitation on the composition is that the (C 3 A) shall not exceed 15%.
- Type II provides moderate sulfate resistance, and gives off less heat during hydration.
This type of cement costs about the same as type I. Its typical compound composition is: 51% (C 3 S), 24% (C 2 S), 6% (C 3 A), 11% (C 4 AF), 2.9% MgO, 2.5% (SO 3 ), 0.8% ignition loss, and 1.0% free CaO. A limitation on the composition is that the (C 3 A) shall not exceed 8%, which reduces its vulnerability to sulfates.
- This type is for general construction exposed to moderate sulfate attack, and is meant for use when concrete is in contact with soils and ground water, especially in the western United States due to the high sulfur content of the soils.
- Because of similar price to that of type I, type II is much used as a general purpose cement, and the majority of portland cement sold in North America meets this specification.
Note: Cement meeting (among others) the specifications for types I and II has become commonly available on the world market. Type III has relatively high early strength. Its typical compound composition is: 57% (C 3 S), 19% (C 2 S), 10% (C 3 A), 7% (C 4 AF), 3.0% MgO, 3.1% (SO 3 ), 0.9% ignition loss, and 1.3% free CaO.
This cement is similar to type I, but ground finer. Some manufacturers make a separate clinker with higher C 3 S and/or C 3 A content, but this is increasingly rare, and the general purpose clinker is usually used, ground to a specific surface area typically 50–80% higher. The gypsum level may also be increased a small amount.
This gives the concrete using this type of cement a three-day compressive strength equal to the seven-day compressive strength of types I and II. Its seven-day compressive strength is almost equal to 28-day compressive strengths of types I and II. The only downside is that the six-month strength of type III is the same or slightly less than that of types I and II.
Therefore, the long-term strength is sacrificed. It is usually used for precast concrete manufacture, where high one-day strength allows fast turnover of molds. It may also be used in emergency construction and repairs, and construction of machine bases and gate installations. Type IV portland cement is generally known for its low heat of hydration.
Its typical compound composition is: 28% (C 3 S), 49% (C 2 S), 4% (C 3 A), 12% (C 4 AF), 1.8% MgO, 1.9% (SO 3 ), 0.9% ignition loss, and 0.8% free CaO. The percentages of (C 2 S) and (C 4 AF) are relatively high and (C 3 S) and (C 3 A) are relatively low.
A limitation on this type is that the maximum percentage of (C 3 A) is seven, and the maximum percentage of (C 3 S) is thirty-five. This causes the heat given off by the hydration reaction to develop at a slower rate. Consequently, the strength of the concrete develops slowly. After one or two years the strength is higher than the other types after full curing.
This cement is used for very large concrete structures, such as dams, which have a low surface to volume ratio. This type of cement is generally not stocked by manufacturers, but some might consider a large special order. This type of cement has not been made for many years, because portland-pozzolan cements and ground granulated blast furnace slag addition offer a cheaper and more reliable alternative.
- Type V is used where sulfate resistance is important.
- Its typical compound composition is: 38% (C 3 S), 43% (C 2 S), 4% (C 3 A), 9% (C 4 AF), 1.9% MgO, 1.8% (SO 3 ), 0.9% ignition loss, and 0.8% free CaO.
- This cement has a very low (C 3 A) composition which accounts for its high sulfate resistance.
- The maximum content of (C 3 A) allowed is 5% for type V portland cement.
Another limitation is that the (C 4 AF) + 2(C 3 A) composition cannot exceed 20%. This type is used in concrete to be exposed to alkali soil and ground water sulfates which react with (C 3 A) causing disruptive expansion. It is unavailable in many places, although its use is common in the western United States and Canada.
- As with type IV, type V portland cement has mainly been supplanted by the use of ordinary cement with added ground granulated blast furnace slag or tertiary blended cements containing slag and fly ash.
- Types Ia, IIa, and IIIa have the same composition as types I, II, and III.
- The only difference is that in Ia, IIa, and IIIa, an air-entraining agent is ground into the mix.
The air-entrainment must meet the minimum and maximum optional specification found in the ASTM manual. These types are only available in the eastern United States and Canada, only on a limited basis. They are a poor approach to air-entrainment which improves resistance to freezing under low temperatures.
Why is cement a mixture?
Hence, cement is a mixture of calcium silicates and aluminates.
What is cement short answer?
Cement is an important material in construction. Sheets, blocks, pillars and pipes are made from concrete produced from cement. Cement is a dry, greenish grey powder with fine particles. It is made from silica (sand), alumina (aluminium oxide), lime, iron oxide and magnesia (magnesium oxide).
What are uses of cement?
Where is cement used? – Cembureau Airports | Green roofs | Bridges | Water pipes | Grain silos | Tunnel | Multi storey car parks | Elevated trains | Swimming pools | High rise office buildings | Water reservoirs | Dikes | Wind Power | Roads | Dams | Cargo ships | Statues | Stairs |High rise residential buildings | Houses Cement plays a key, but often unnoticed, role in our lives.
Cement is mainly used as a binder in concrete, which is a basic material for all types of construction, including housing, roads, schools, hospitals, dams and ports, as well as for decorative applications (for patios, floors, staircases, driveways, pool decks) and items like tables, sculptures or bookcases.
Concrete is a versatile and reliable construction material with a wide range of applications. When looking at possible pathways to reduce the carbon footprint of the European cement industry, it is important to examine some of the characteristics of the industry that will influence the availability or viability of emission reduction options. The cement industry is CO 2 -, energy- and material-intensive. Measures to decrease energy consumption and to improve resource efficiency will de facto, reduce CO 2 emissions (hence the focus on CO 2 emissions). The combination of process emissions (emissions released when limestone is transformed into lime during the production process) and emissions from the required thermal energy leads to substantial CO2emissions for each tonne of cement. The cost of constructing a new cement plant with 1 million tonnes of annual capacity is typically more than €150 million. Modernisation of existing cement plants is also very expensive. In addition, and in order to meet European environmental legislation, operations face major investments and operating costs.30% of the cement industry’s total operating expenses relate to energy costs.
The cost of a new cement plant is equivalent to around three years of turnover, which ranks the cement industry among the most capital-intensive industries. Long periods are therefore needed before these large investments can be recovered. Plant modifications have to be carefully planned, as typical investment cycles in the sector last about 30 years.
Consequently, achieving the 2050 low-carbon economy roadmap for the European cement industry will be based on balancing recent investments with planning new investments in the coming decades. Although produced from naturally occurring raw materials that can vary widely from plant to plant, cement is a product manufactured in Europe according to a harmonised standard. Despite the existence of specialised segments, many cements are interchangeable, which promotes a competitive cement market. This also means that European production can be very vulnerable to cheaper imports. Cement is mostly locally produced and locally consumed. However, it is also transported over long distances by sea, river and land as plants rationalise and exploit efficiencies of scale. Land transportation costs are significant. Transporting cement costs about €10 per tonne for every 100km by road and around €15 per tonne to cross the Mediterranean Sea 2, Cement consumption is closely linked to economic development in the local region or country. In mature markets, such as Europe, where cement consumption per capita still varies considerably from one country to another, cement sales are dependent on activity in the construction sector, which closely follows (usually after a brief delay) general economic activity.
Why limestone is used in cement?
Incorporating superfluous fine limestone powder or coarse limestone powder increases the porosity of cement-based materials due to dilution effect. The chemical effect of limestone powder generates carboaluminate, stabilizes the ettringite and thus reduces the porosity of cement-based materials.
Why is it called gypsum?
3. It was named by the Ancient Greeks – The name “gypsum” is derived from the ancient Greek word “gypsos,” which means plaster. The ancient Greeks used a form of gypsum in the windows of their temples because of the moonlight effect it created on the altars when the sun shone through.
Why fly ash is used in cement?
Introduction – The use of fly ash in portland cement concrete (PCC) has many benefits and improves concrete performance in both the fresh and hardened state. Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete.
Improved workability. The spherical shaped particles of fly ash act as miniature ball bearings within the concrete mix, thus providing a lubricant effect. This same effect also improves concrete pumpability by reducing frictional losses during the pumping process and flat work finishability. Figure 3-1: Fly ash improves workability for pavement concrete. Decreased water demand. The replacement of cement by fly ash reduces the water demand for a given slump. When fly ash is used at about 20 percent of the total cementitious, water demand is reduced by approximately 10 percent. Higher fly ash contents will yield higher water reductions. The decreased water demand has little or no effect on drying shrinkage/cracking. Some fly ash is known to reduce drying shrinkage in certain situations. Reduced heat of hydration. Replacing cement with the same amount of fly ash can reduce the heat of hydration of concrete. This reduction in the heat of hydration does not sacrifice long-term strength gain or durability. The reduced heat of hydration lessens heat rise problems in mass concrete placements.
Benefits to Hardened Concrete. One of the primary benefits of fly ash is its reaction with available lime and alkali in concrete, producing additional cementitious compounds. The following equations illustrate the pozzolanic reaction of fly ash with lime to produce additional calcium silicate hydrate (C-S-H) binder:
|Cement Reaction:||C 3 S +||H → C-S-H + CaOH|
|Pozzolanic Reaction:||CaOH +||S → C-S-H|
|silica from ash constituents|
ul> Increased ultimate strength. The additional binder produced by the fly ash reaction with available lime allows fly ash concrete to continue to gain strength over time. Mixtures designed to produce equivalent strength at early ages (less than 90 days) will ultimately exceed the strength of straight cement concrete mixes (see Figure 3-2).
Figure 3-2: Typical strength gain of fly ash concrete.
Reduced permeability. The decrease in water content combined with the production of additional cementitious compounds reduces the pore interconnectivity of concrete, thus decreasing permeability. The reduced permeability results in improved long-term durability and resistance to various forms of deterioration (see Figure 3-3)
Figure 3-3: Permeability of fly ash concrete.
Improved durability. The decrease in free lime and the resulting increase in cementitious compounds, combined with the reduction in permeability enhance concrete durability. This affords several benefits:
Improved resistance to ASR. Fly ash reacts with available alkali in the concrete, which makes them less available to react with certain silica minerals contained in the aggregates. Improved resistance to sulfate attack. Fly ash induces three phenomena that improve sulfate resistance:
Fly ash consumes the free lime making it unavailable to react with sulfate The reduced permeability prevents sulfate penetration into the concrete Replacement of cement reduces the amount of reactive aluminates available
Improved resistance to corrosion. The reduction in permeability increases the resistance to corrosion.
Figure 3-4: Fly ash concrete is used in severe exposure applications such as the decks and piers of Tampa Bay’s Sunshine Skyway Bridge.
Which chemical is mix in cement?
Calcium chloride is a commonly used effective and economical accelerators, which is available in liquid or flake form. Calcium chloride must meet the requirements of ASTM D98. For non- reinforced concrete, calcium chloride can be used to a limit of 2% by the weight of the cement.
What are the three 3 ingredients of concrete?
Contrary to popular belief, concrete and cement are not the same thing; cement is actually just a component of concrete. Concrete is made up of three basic components: water, aggregate (rock, sand, or gravel) and Portland cement. Cement, usually in powder form, acts as a binding agent when mixed with water and aggregates.
This combination, or concrete mix, will be poured and harden into the durable material with which we are all familiar. Find concrete contractors near me, Following is a group of articles that will be helpful when trying to understand more about concrete and cement. Other items that might be of interest to you include concrete basics such as mix design, and cement information,
Popular Concrete Topics: What is Concrete? Time: 00:52 What is concrete made of? Portland cement, aggregate, sand, etc. Find Concrete Ready Mix Suppliers Article Contents: Components of a Basic Concrete Mix Desired Properties of Concrete Concrete Admixtures Concrete Reinforcement: Fibers vs.
Portland Cement Water Aggregates (rock and sand)
Portland Cement – The cement and water form a paste that coats the aggregate and sand in the mix. The paste hardens and binds the aggregates and sand together. Water – Water is needed to chemically react with the cement (hydration) and too provide workability with the concrete.
The amount of water in the mix in pounds compared with the amount of cement is called the water/cement ratio. The lower the w/c ratio, the stronger the concrete. (higher strength, less permeability) Aggregates – Sand is the fine aggregate. Gravel or crushed stone is the coarse aggregate in most mixes. Podcast: Hear Jim Peterson, founder of ConcreteNetwork.com, answer top concrete questions on the Ask Danny podcast from Today’s Homeowner,
Desired Properties of Concrete 1. The concrete mix is workable, It can be placed and consolidated properly by yourself or your workmen.2. Desired qualities of the hardened concrete are met: for example, resistance to freezing and thawing and deicing chemicals, watertightness (low permeability), wear resistance, and strength.
use the stiffest mix possible use the largest size aggregate practical for the job. Use the optimum ratio of fine to coarse aggregate.
Discuss how to achieve your goals for the concrete with your ready mix supplier. Concrete Admixtures: Most Common Types and What They Do Admixtures are additions to the mix used to achieve certain goals. Here are the main admixtures and what they aim to achieve.
Accelerating admixture- accelerators are added to concrete to reduce setting time of the concrete and to accelerate early strength. The amount of reduction in setting time varies depending on the amount of accelerator used (see your ready mix supplier and describe your application). Calcium chloride is a low cost accelerator, but specifications often call for a nonchloride accelerator to prevent corrosion of reinforcing steel.
Retarding admixtures -Are often used in hot weather conditions to delay setting time. They are also used to delay set of more difficult jobs or for special finishing operations like exposing aggregate. Many retarders also act as a water reducer. Fly Ash – Is a by product of coal burning plants.
Fly ash improves workability Fly ash is easier to finish Fly ash reduces the heat generated by the concrete Fly ash costs to the amount of the cement it replaces
Air Entraining Admixtures – must be used whenever concrete is exposed to freezing and thawing, and to deicing salts. Air entraining agents entrains microscopic air bubbles in the concrete: when the hardened concrete freezes, the frozen water inside the concrete expands into these air bubbles instead of damaging the concrete.
Air entrainment improves concrete workability Air entrainment improves durability Air entrainment produces a more workable mix
Water reducing admixtures -reduces the amount of water needed in the concrete mix. The water cement ratio will be lower and the strength will be greater. Most low range water reducers reduce the water needed in the mix by 5%-10%. High range water reducers reduce the mix water needed by 12% to 30% but are very expensive and rarely used in residential work.
Concrete Reinforcement: Fibers vs. Welded Wire Mesh Fibers can be added to the concrete mix in lieu of welded wire mesh. The problem with welded wire mesh is that it often ends up on the ground from being stepped on as the concrete is being placed. (particularly if no support blocks are used). Another problem is that mesh does not prevent or minimize cracking-it simply holds cracks that have already occurred together.
If you could look into a section of concrete poured with fibers you would see millions of fibers distributed in all directions throughout the concrete mix. As micro cracks begin to appear due to shrinkage as water evaporates form the concrete (plastic shrinkage), the cracks intersect with the fibers which block their growth and provide higher tensile strength capacity at this crucial time.
Click here for how fibers are an important part of ” how to build high quality slabs on grade.” ADJUSTING CONCRETE MIXES TO CORRECT PLACING PROBLEMS When the concrete sticks to the trowel when it is lifted off the concrete, or concrete sticks to the finishers kneeboards, too much sand in the mix or higher than necessary air entrainment are most likely the causes.
Excessive bleedwater will delay the finishing operation and can cause serious problems with the surface of the concrete. Adding more sand to the mix, adding more entrained air, using less mix water, or adding cement or fly ash are possible cures. Make sure your ready mix supplier knows if you will be pumping concrete.
Pumping mixes require a sufficient amount of fines and there are limits to the size of the aggregate in order for the mix to be pumpable. Fly ash and air entrainment improve workability and pumpability. Setting time of the mix can be slowed with retarders. The mix may be cooled in hot weather by replacing part of the mixing water with ice, sprinkling water on the aggregate pile at the ready mix plant, or injecting liquid nitrogen into the batch.
Setting time of the mix can be sped up with accelerators. The mix can be heated at the ready mix plant by heating the mix water and aggregates. Installing Concrete Placing Concrete Normal concrete weighs approximately 150 pounds per cubic foot and should be placed as near as possible to its final position.
Excess handling can cause segregation of the course and fine aggregates. Wetting up the concrete so it can be raked or pushed into a location far from where it is discharged is not acceptable. Concrete is poured directly from the chute of the ready mix truck, wheeled into place with a buggy, or pumped into place with a concrete boom pump (see concrete pumping ).
Concrete is normally specified at a 4-5″ slump. Industrial, commercial, and some residential projects require an inspector on concrete pours who monitors the concrete slump and takes slump measurements at the required intervals. Also see, How To Build High Quality Slabs on Grade Spreading Concrete The purpose of spreading fresh concrete is to place concrete as close as possible to finish level to facilitate straightedging/screeding the concrete.
Short handled, square ended shovels are recommended for spreading concrete. A come-along (a tool that looks like a hoe and has a long straight edged blade) can also be used. Do not use a round edge shovel for spreading concrete since it does not spread the concrete evenly. Any spreader used should be rigid enough to push and pull wet concrete without bending: Normal concrete weighs approximately 150 pounds per cubic foot.
Cold weather concreting Hot weather concreting Curing concrete Decorative Concrete Introduction to decorative concrete Decorative concrete glossary Concrete countertop glossary Concrete History : An Interactive Timeline Concrete Contractors: Find A Concrete Product Supplier or Distributor Other Concrete Resources What is Concrete?- University of Illinois Urbana-Champaign Concrete Industry Management- Middle Tennessee State University ACI Free Downloads- American Concrete Institute (ACI) Cement and Concrete Basics- Portland Cement Association (PCA)
What is cement glue made of?
A bottle of rubber cement, showing a brush built into its cap and a photo about to be cemented to graph paper, Rubber cement ( cow gum in British English ) is an adhesive made from elastic polymers (typically latex ) mixed in a solvent such as acetone, hexane, heptane or toluene to keep it fluid enough to be used.