Portland cement is made up of four main compounds : tricalcium silicate (3CaO · SiO 2 ), dicalcium silicate (2CaO · SiO 2 ), tricalcium aluminate (3CaO · Al 2 O 3 ), and a tetra-calcium aluminoferrite (4CaO · Al 2 O 3 Fe 2 O 3 ).
- 1 Which of the following compounds is cement?
- 2 What are the 4 compounds?
Which of the following compounds is cement?
|Calcium oxide (lime)
|Silicon dioxide (silica)
|Aluminum oxide (alumina)
|Al 2 O 3
|Fe 2 O 3
What are the components of 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 not used for portland cement Mcq?
Detailed Solution. Tricalcium phosphate (Ca3PO4) is NOT present in Portland Cement.
What are the 3 composition 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)
Why cement is a compound?
🕑 Reading time: 1 minute Compounds in cement mainly are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium alumino ferrite. Not only do these compounds control most of cement properties but also reacts with water to produce new materials (cement hydration) and consequently responsible for concrete strength.
For instance, tricalcium silicate hydrates and hardens rapidly, hence generates heat greatly whereas hydration of the other three compounds are slow and consequently heat of hydration would be much lower. It is demonstrated that tricalcium silicate and dicalcium silicate provide most of concrete strength, but the contribution of tricalcium aluminate and tetracalcium alumino ferrite to the concrete strength are considerably low both at early strength and at ultimate strength.
It is worth mentioning that tricalcium silicate is the only compound that provide high early strength to concrete.
What are the 4 compounds?
The chemical compounds of living things are known as organic compounds because of their association with organisms and because they are carbon-containing compounds. Organic compounds, which are the compounds associated with life processes, are the subject matter of organic chemistry.
- Among the numerous types of organic compounds, four major categories are found in all living things: carbohydrates, lipids, proteins, and nucleic acids.
- Carbohydrates Almost all organisms use carbohydrates as sources of energy.
- In addition, some carbohydrates serve as structural materials.
- Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen and carbon atoms is 2:1.
Simple carbohydrates, commonly referred to as sugars, can be monosaccharides if they are composed of single molecules, or disaccharides if they are composed of two molecules. The most important monosaccharide is glucose, a carbohydrate with the molecular formula C 6 H 12 O 6,
Glucose is the basic form of fuel in living things. In multicellular organisms, it is soluble and is transported by body fluids to all cells, where it is metabolized to release its energy. Glucose is the starting material for cellular respiration, and it is the main product of photosynthesis (see Chapters 5 and 6).
Three important disaccharides are also found in living things: maltose, sucrose, and lactose. Maltose is a combination of two glucose units covalently linked. The table sugar sucrose is formed by linking glucose to another monosaccharide called fructose. Figure 2-2 Glucose and fructose molecules combine to form the disaccharide sucrose. Complex carbohydrates are known as polysaccharides. Polysaccharides are formed by linking innumerable monosaccharides. Among the most important polysaccharides is starch, which is composed of hundreds or thousands of glucose units linked to one another.
- Starch serves as a storage form for carbohydrates.
- Much of the world’s human population satisfies its energy needs with starch in the form of rice, wheat, corn, and potatoes.
- Two other important polysaccharides are glycogen and cellulose.
- Glycogen is also composed of thousands of glucose units, but the units are bonded in a different pattern than in starch.
Glycogen is the form in which glucose is stored in the human liver. Cellulose is used primarily as a structural carbohydrate. It is also composed of glucose units, but the units cannot be released from one another except by a few species of organisms. Wood is composed chiefly of cellulose, as are plant cell walls.
- Cotton fabric and paper are commercial cellulose products.
- Lipids Lipids are organic molecules composed of carbon, hydrogen, and oxygen atoms.
- The ratio of hydrogen atoms to oxygen atoms is much higher in lipids than in carbohydrates.
- Lipids include steroids (the material of which many hormones are composed), waxes, and fats.
Fat molecules are composed of a glycerol molecule and one, two, or three molecules of fatty acids (see Figure 2-3). A glycerol molecule contains three hydroxyl (–OH) groups. A fatty acid is a long chain of carbon atoms (from 4 to 24) with a carboxyl (–COOH) group at one end.
- The fatty acids in a fat may all be alike or they may all be different.
- They are bound to the glycerol molecule by a process that involves the removal of water.
- Certain fatty acids have one or more double bonds in their molecules.
- Fats that include these molecules are unsaturated fats.
- Other fatty acids have no double bonds.
Fats that include these fatty acids are saturated fats. In most human health situations, the consumption of unsaturated fats is preferred to the consumption of saturated fats. Fats stored in cells usually form clear oil droplets called globules because fats do not dissolve in water. Figure 2-3 A fat molecule is constructed by combining a glycerol molecule with three fatty acid molecules. (Two saturated fatty acids and one unsaturated fatty acid are shown for comparison.) The constructed molecule is at the bottom. Proteins Proteins, among the most complex of all organic compounds, are composed of amino acids (see Figure 2-4), which contain carbon, hydrogen, oxygen, and nitrogen atoms. Figure 2-4 The structure and chemistry of amino acids. When two amino acids are joined in a dipeptide, the –OH of one amino acid is removed, and the –H of the second is removed. So, water is removed. A dipeptide bond (right) forms to join the amino acids together.
Many proteins are immense and extremely complex. However, all proteins are composed of long chains of relatively simple amino acids. There are 20 kinds of amino acids. Each amino acid (see the left illustration in Figure 2-4) has an amino (–NH 2 ) group, a carboxyl (–COOH) group, and a group of atoms called an –R group (where R stands for radical ).
The amino acids differ depending on the nature of the –R group, as shown in the middle illustration of Figure 2-4. Examples of amino acids are alanine, valine, glutamic acid, tryptophan, tyrosine, and histidine. The removal of water molecules links amino acids to form a protein.
The process is called dehydration synthesis, and a by-product of the synthesis is water. The links forged between the amino acids are peptide bonds, and small proteins are often called peptides. All living things depend on proteins for their existence. Proteins are the major molecules from which living things are constructed.
Certain proteins are dissolved or suspended in the watery substance of the cells, while others are incorporated into various structures of the cells. Proteins are also found as supporting and strengthening materials in tissues outside of cells. Bone, cartilage, tendons, and ligaments are all composed of proteins.
One essential function of proteins is as an enzyme. Enzymes catalyze the chemical reactions that take place within cells. They are not used up in a reaction; rather, they remain available to catalyze succeeding reactions. Every species manufactures proteins unique to that species. The information for synthesizing the unique proteins is located in the nucleus of the cell.
The so-called genetic code specifies the amino acid sequence in proteins. Hence, the genetic code regulates the chemistry taking place within a cell. Proteins also can serve as a reserve source of energy for the cell. When the amino group is removed from an amino acid, the resulting compound is energy-rich.
- Nucleic acids Like proteins, nucleic acids are very large molecules.
- The nucleic acids are composed of smaller units called nucleotides.
- Each nucleotide contains a carbohydrate molecule (sugar), a phosphate group, and a nitrogen-containing molecule that, because of its properties, is a nitrogenous base.
Living organisms have two important nucleic acids. One type is deoxyribonucleic acid, or DNA. The other is ribonucleic acid, or RNA. DNA is found primarily in the nucleus of the cell, while RNA is found in both the nucleus and the cytoplasm, a semiliquid substance that composes the volume of the cell (see Chapter 3).
What are the 4 chemical compounds?
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities ) containing atoms from more than one chemical element held together by chemical bonds, A molecule consisting of atoms of only one element is therefore not a compound.
- A compound can be transformed into a different substance by a chemical reaction, which may involve interactions with other substances.
- In this process, bonds between atoms may be broken and/or new bonds formed.
- There are four major types of compounds, distinguished by how the constituent atoms are bonded together.
Molecular compounds are held together by covalent bonds ; ionic compounds are held together by ionic bonds ; intermetallic compounds are held together by metallic bonds ; coordination complexes are held together by coordinate covalent bonds, Non-stoichiometric compounds form a disputed marginal case.
What is Portland cement Class 12?
What is Portland cement concrete? Get to know the Answer at BYJU’S UPSC Preparation Portland cement is a type of cement obtained by pulverizing clinker, consisting of hydraulic calcium silicates to which some calcium sulfate has usually been provided as an interground addition.
15.3.1 Make-up of Portland cement – Portland cement is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of gypsum (calcium sulphate dehydrate – CaSO4.2H2O, which controls the set time) and other minor constituents which can be used to vary the properties of the final cement.
The standard Portland cement is often referred to as Ordinary Portland Cement, and European Standard EN197-1 gives the following description: Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO.SiO 2 and 2CaO.SiO 2 ), the remainder consisting of aluminium and iron containing clinker phases and other compounds.
The ratio of CaO to SiO 2 shall not be less than 2.0. The magnesium oxide content (MgO) shall not exceed 5.0% by mass. The US Standard ASTM C 150 defines Portland cement as: Hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverising clinkers consisting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulphate as an inter-ground addition.
- Note: The term ‘hydraulic’ when related to cement materials refers to the property of the material to harden by reacting with water as well as the material’s ability to form a water-resistant product.
- Portland cement clinker is nodules (diameters, 5–25 mm) of sintered material produced by heating a homogeneous mixture of raw materials in a kiln to a sintering temperature of approximately 1450 °C for modern cements.
The resulting clinker consists of four main minerals: 11 1. Alite or tricalcium silicate, Ca 3 SiO 5 (in oxide terms 3CaO.SiO 2 ), abbreviated to C 3 S; 2. Belite or dicalcium silicate, Ca 2 SiO 4 (in oxide terms 2CaO.SiO 2 ), abbreviated to C 2 S; 3. Tricalcium aluminate, CaAl 2 O 6 (in oxide terms 3CaO.SiO 3 ), abbreviated to C 3 A; 4.
- Tetracalcium alumino-ferrite, Ca 2 AlFeO 5 (in oxide terms 4CaO.Al 2 O3.
- Fe 2 O 3 ), abbreviated to C 4 AF.
- The aluminium oxide and iron oxide are present in the main as a flux and contribute little to the mechanical strength of the final concrete.
- The proportions of each mineral in the clinker are important in determining the properties of the resulting cement.
For example, in some special cements, such as Low Heat (LH) and Sulphate Resistant (SR) types, it is necessary to limit the amount of tricalcium aluminate (3CaO-Al 2 O 3 ) that is formed. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781782421160500153
What are the minor compounds in portland cement?
Minor constituents it’s the oxides less than 10% of cements weight which consists of magnesia (MgO), alkali oxides (Na2O and K2O), titania (TiO2), phosphorous pentoxide (P2O5) and gypsum.