Manufacturing – Although there are several variations of commercially manufactured portland cement, they each share many of the same basic raw materials and chemical components. The chief chemical components of portland cement are calcium, silica, alumina and iron.
- Calcium is derived from limestone, marl or chalk, while silica, alumina and iron come from the sands, clays and iron ore sources.
- Other raw materials may include shale, shells and industrial byproducts such as mill scale (Ash Grove Cement Company, 2000 ).
- The basic manufacturing process heats these materials in a kiln to about 1400 to 1600°C (2600 – 3000°F) – the temperature range in which the two materials interact chemically to form calcium silicates (Mindess and Young, 1981 ).
This heated substance, called ” clinker ” is usually in the form of small gray-black pellets about 12.5 mm (0.5 inches) in diameter. Clinker is then cooled and pulverized into a fine powder that almost completely passes through a 0.075 mm (No.200) sieve and fortified with a small amount of gypsum.
- 1 Which of the following is main ingredient of Portland cement?
- 2 What is the main ingredient in cement?
- 3 What is the ordinary Portland cement?
- 4 Is Gypsum main ingredient of cement?
- 5 Why is ordinary Portland cement used?
- 6 What minerals are in portland cement?
- 7 Does portland cement contain silica?
Which of the following is main ingredient of Portland cement?
The important ingredients present in Portland Cement are dicalcium silicate (Ca2SiO4)) (26%), tricalcium silicate (Ca3SiO5)) (51%), tricalcium aluminate (Ca3Al2O6)) (11%).
What 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.
What is Portland cement made of?
18.1.1 Portland cement – Portland cement is obtained by heating limestone and clay or other silicate mixtures at high temperatures (>1500°C) in a rotating kiln. The resulting clinker, when cooled, is mixed with gypsum (calcium sulfate) and ground to a highly uniform fine powder. Anhydrous Portland cement consists mainly of lime (CaO), silica (SiO 2 ), and alumina (Al 2 O 3 ), in addition to small amounts of magnesia (MgO), ferric oxide (Fe 2 O 3 ), sulfur trioxide (SO 3 ), and other oxides that are added as impurities in the raw materials during its manufacture. When these oxides are blended together, they form the four basic components of Portland cement, namely: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. Table 18.1 describes the main oxide compositions, their chemical formulas, and abbreviations, in addition to listing the average of each in commercially available ordinary Portland cement (OPC) (wt.%), Table 18.1, The main oxide compositions, their oxide formulas, and abbreviations in addition to the average of each in commercially available Portland cement (wt.%).
|Oxide constituent||Oxide composition and abbreviation||Average weight (%)|
|Tricalcium silicate||3CaO·SiO 2 (C 3 S)||40–60|
|Dicalcium silicate||2CaO·SiO 2 (C 2 S)||13–50|
|Tricalcium aluminate||3CaO·Al 2 O 3 (C 3 A)||4–11|
|Tetracalcium aluminoferrite||4CaO·Al 2 O 3 ·Fe 2 O 3 (C 4 AF)||7–13|
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What is the ordinary Portland cement?
4.2.2 Ordinary Portland Cement – Ordinary Portland cement (simply called ordinary cement) refers to the hydraulic binding material ground by mixing Portland cement clinker, 6% ~ 15% blended materials, and appropriate amount of gypsum, code-named P• O.
The maximum amount of active blended materials mixed in cement should not exceed 15% of the total mass. They are allowed to be replaced by kiln ash and inactive blended materials which should be no more than 5% and 10% of the cement mass respectively. The maximum amount of inactive blended materials mixed in cement should not exceed 10% of the total mass.
According to Portland Cement, Ordinary Portland Cement (GB175-1999), the national standard, the strength grades of ordinary cement can be divided into: 32.5, 32.5 R, 42.5, 42.5 R, 52.5, 52.5 R, and their ages should be no less than the numerical value in Table 4.3,
The initial setting time of ordinary cement should not be earlier than 45 min, and final setting time should not be later than 10 h. The screenings left on the square-hole sieve of 0.08 mm should not exceed 10%. And boiling stability must be qualified. The ignition loss of cement should be less than 5.0%.
Table 4.3, Requirements for the Strength of Ordinary Portland Cement at Various Ages (GB175-1999)
|Strength Grade||Compressive Strength (MPa)||Bending Strength (MPa)|
Note: R——rapid strengthening type. The majority of ordinary Portland cement is Portland cement clinker whose performance is similar to Portland cement. Due to the mixture of a few blended materials, however, the early hardening rate of the Portland cement linker is slow, 3d compressive strength is low, and the frost-resistance and wear-resistance are relatively poor, compared with Portland cement.
Is Gypsum main ingredient of cement?
The ingredients of cement are lime (CaO), clay, silica along with some other oxides of aluminium, iron and magnesium. Gypsum (CaSO4,2H2O) is usually added to regulate the setting rate of cement. Was this answer helpful?
Which of the following is not an ingredient of Portland cement?
Tricalcium phosphate (Ca3PO4) is NOT present in Portland Cement.
Why is ordinary Portland cement used?
OPC is a general purpose Portland cement suitable for all uses where the special properties of other types are not required. It is used where cement or concrete is not subject to specific exposures, such as sulfate attack from soil or water, or to an objectionable temperature rise due to heat generated by hydration.
What minerals are in portland cement?
Portland cement consists of four main compounds listed in order of their importance: β-dicalcium silicate (β-Ca 2 SiO 4 ), tricalcium silicate (Ca 3 SiO 5 ), tricalcium aluminate (Ca 3 Al 2 O 6 ), and calcium aluminoferrite (Ca 2 AlFeO 5 ).
What are the two types of portland cement?
The standard types of portland cement are: Type I – for general purpose. Type IA – same as Type I, but when air entrainment is desired. Type II – for moderate sulfate resistance.
Does portland cement contain silica?
PORTLAND CEMENT OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force. CAS: 65997-15-1; Chemical Formula: None OSHA formerly had a limit of 50 mppcf (approximately 15 mg/m 3 ) for Portland cement containing less than 1 percent crystalline silica.
The ACGIH has a TLV-TWA of 10 mg/m 3 for Portland cement as total dust containing less than 1 percent quartz. The proposed PEL was 10 mg/m 3, measured as total particulate, and this is the limit established in the final rule; the 5-mg/m 3 respirable fraction limit is retained. Portland cement refers to a class of hydraulic cements that are odorless gray powders containing less than 1 percent crystalline silica.
Portland cement is insoluble in water and contains tri- and dicalcium silicate, in addition to varying amounts of alumina, tricalcium aluminate, and iron oxide. Intraperitoneal injection of Portland cement in guinea pigs produced an absorptive reaction, which is an effect typical of inert particulates.
- Portland cement is eventually eliminated from the tissue and is generally not considered harmful when ingested (Miller and Sayers 1941/Ex.1-595).
- In a study of industrial exposures, Gardner and associates (1939/Ex.1-589) found no evidence of Portland-cement-related pneumoconiosis in 2,278 workers who had been heavily exposed to this substance for prolonged periods of time (Gardner, Durkan, Brumfiel, and Sampson 1939/Ex.1-589).
Conflicting reports of pneumoconiosis (Parmeggiani 1951, as cited in ACGIH 1986/ Ex.1-3, p.494; Prosperi and Barsi 1957/Ex.1-1093) are attributed to the presence of silica in the inhaled dust rather than to exposure to Portland cement itself (ACGIH 1986/Ex.1-3, p.494).
Cement dermatitis does occur among exposed workers, however, as a consequence of the alkaline, abrasive, and hygroscopic properties of the wet cement, which cause irritation of the skin (Schwartz, Tulipan, and Birmingham 1957a/Ex.1-1168). NIOSH, the only commenter on this substance, reported that it has not thoroughly reviewed the health effects for Portland cement (Ex.8-47, Table N4).
OSHA is establishing 8-hour TWA PELs of 10 mg/m 3 (total particulate) and 5 mg/m 3 (respirable fraction) for Portland cement containing less than 1 percent quartz. The Agency concludes that these limits will protect workers against the significant risks associated with on-the-job exposures to Portland cement dust.
These risks include eye, skin, and mucous membrane irritation, and may include more severe respiratory effects, all of which constitute material health impairments. In addition, revising the total particulate limit to 10 mg/m 3 as an 8-hour TWA will simplify employee exposure monitoring for Portland cement, since gravimetric rather than impinger methods can then be used.
: PORTLAND CEMENT
What ingredients make up Portland cement quizlet?
Portland cement is made by mixing calcareous material, like limestone, with silica, alumina, and iron oxide-containing materials. These materials are burned together and the resulting product, or admixture, is ground up to form Portland cement.
What are the main oxides found in Portland cement?
Four main oxides present in ordinary Portland cement are CaO,Al2O3SiO2 and Fe2O3. Identify the correct ascending order of their proportions in a typical composition of OPC No worries! We‘ve got your back. Try BYJU‘S free classes today! No worries! We‘ve got your back. Suggest Corrections 1 : Four main oxides present in ordinary Portland cement are CaO,Al2O3SiO2 and Fe2O3. Identify the correct ascending order of their proportions in a typical composition of OPC