Hint: We must know that the portland cement is a common material and is the basic ingredient of concrete. Portland cement forms a paste with water that hardens on binding with sand and rock. Complete step by step answer: We can use portland cement popularly as a binding material in the form of a finely ground powder that is prepared by burning and grinding a mixture of limestone and clay or limestone and shell.
When it is mixed with water, the Constituents of Portland cement reacts chemically with the water that leads to the process of hydration and decomposition or hydrolysis. These processes make the mixture harden and thus it develops strength. Portland cement is composed of following chemicals, namely, \ ( tricalcium aluminate), \ ( tricalcium silicate), \ ( Dicalcium silicate), \ (Sodium oxide), \ (Potassium oxide), \ (Calcium sulfate dihydrate ) and \ (Tetracalcium- aluminatferrite) The Portland cement is composed of 60% calcium oxide, 25% silica, 7% of alumina, 2 to 2.5% magnesia and 2 to 2.5% ferric oxide.
We know calcium silicates and calcium aluminates are forms of Calcium oxide. So, Portland cement does not contain calcium phosphate. $\therefore $The correct option is the option D. Additional information: We must know that Joseph Aspdin from England is the inventor of the basic process of Portland cement manufacturing.
Portland cement has been named so for the resemblance of the cement when set to portland stone from the Isle of Portland. There are five types of Portland cement available in the world market depending upon their content, properties and usage. Percentage of above mentioned contents of Portland cement varies from type to type.
Note: Calcium phosphate has nutritive value; we can use it as an antacid and also as a dietary supplement in veterinary medicines. It is used in medicine as a calcium supplement dose.
- 1 What are the 4 components of cement?
- 2 What are the 3 components of concrete?
- 3 Which of the following oxide is not a part of composition of Portland cement?
- 4 What are the 5 composition of concrete?
- 5 What is Type 10 Portland cement?
- 6 Is Portland cement type of cement?
- 7 What is Type 4 Portland cement used for?
- 8 What are 3 common raw materials to manufacture portland cement?
- 9 What is the main ingredient in ordinary portland cement?
What are the components 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
Which is not a part 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.
What are the 4 components of cement?
Chemical composition 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 ).
How many types of Portland cement are there?
TYPE IA, IIA, IIIA Specifications for three types of air-entraining portland cement (Types IA, IIA, and IIIA) are given in ASTM C 150.
What are the 3 components 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)
Which of the following oxide is not a part of composition of Portland cement?
Calcium oxide is present in the form of calcium silicates and calcium aluminates. Portland cement does not contain calcium phosphate.
Which material is not used in cement industry?
Which of the following is not a raw material used in the cement industry ?(A) Limestone(B) Silica(C) Manganese (D) Gypsum Answer Verified Hint: It is a mineral present in various plants, such as almonds, legumes, beans, tea, whole grains, and green leafy vegetables.
- As the body needs it to function correctly, it is called an essential food.
- They are used by people as medicine.
- Complete answer: For construction activities, such as building homes, factories, bridges, highways, airports, dams and other commercial establishments, cement is important.
- Manganese is often used by the steel industry in deoxidizing and desulfurizing additives and as an alloying constituent.
On the other hand Manganese is an important raw material for the iron and steel industry. In this industry, roomy and heavy raw materials such as limestone, silica, alumina and gypsum are required. There are 128 large plants and 332 small cement plants in the region Iron and steel is a heavy industry where both raw materials and finished products are heavy and voluminous, resulting in heavy shipping costs.A new method of introducing manganese in High Alumina cements can be obtained by using manganese raw materials already in mixing up the raw meal before sintering.
By the addition of manganese sulphate to High Alumina cements a control of hydration similarly as by the use of gypsum can be obtained, despite other hydration products being formed. In the iron and steel industry, manganese is an important raw material since it is used to harden steel and keep it from rusting.
It is found in batteries consisting of dry cells It is used in the manufacturing of a number of alloys. It is used in the electrical, glass and chemical sectors. So the correct answer is option (C) Manganese. Note: The ready availability of raw materials for producing cement is an essential factor that supports the growth of this industry.
What are 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 the main components of cement?
Portland cement consists essentially of compounds of lime (calcium oxide, CaO) mixed with silica (silicon dioxide, SiO2) and alumina (aluminium oxide, Al2O3). The lime is obtained from a calcareous (lime-containing) raw material, and the other oxides are derived from an argillaceous (clayey) material.
What are the 5 composition of 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.
What is Type 3 Portland cement used for?
TDS. TCC.100722 PRODUCT DESCRIPTION Portland Cement Type III is a low-alkali, special purpose hydraulic cement used to make concrete for a variety of building construction, repairs, grouts, or mortar applications where higher early strength than Type I-II Portland is needed.
What is Type 10 Portland cement?
The store will not work correctly in the case when cookies are disabled. Part number 60.14.S30 (6011S30) A general purpose cement, suitable for most projects requiring cement. It is used in the majority of concrete and sand-cement mixes. The amount of cement used in the mix depends on the properties required.
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Is Portland cement type of cement?
This article is about the building product of cement. For the Australian heritage-listed production site, see Portland Cement Works Precinct, Bags of portland cement wrapped and stacked on a pallet. Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout, It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and is usually made from limestone,
- It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum,
- Several types of portland cement are available.
- The most common, called ordinary portland cement (OPC), is grey, but white Portland cement is also available.
Its name is derived from its resemblance to Portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of “modern” portland cement due to his developments in the 1840s.
What is Type 4 Portland cement?
TYPES OF CEMENT AND WHAT THEY DO – Portland Cement is a type of cement, not a brand name. Many cement manufacturers make Portland Cement. It is a basic ingredient of concrete, made using a closely controlled chemical combination of calcium, silicon, aluminum, iron and small amounts of other ingredients to which gypsum is added in the final grinding process to regulate the setting time of the concrete.
The Portland Cement Association’s How cement is made provides detailed information of the process. To find out more about what concrete is made of, concrete mix designs, admixtures, and water to cement ratios, read our section ” What Is Concrete ?” Type 1 – Normal portland cement. Type 1 is a general use cement.
Type 2 – Is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern. Type 3 – High early strength. Used when high strength are desired at very early periods. Type 4 – Low heat portland cement. Used where the amount and rate of heat generation must be kept to a minimum.
- Type 5 – Sulfate resistant portland cement.
- Used where the water or soil is high in alkali.
- Types IA, IIA and IIIA are cements used to make air-entrained concrete.
- They have the same properties as types I, II, and III, except that they have small quantities of air-entrained materials combined with them.
Types IL, IS, IP and It are blended hydraulic cements that offer a variety of special performance properties. A cement factory (Juan Enrique del Barrio / Shutterstock). These are very short descriptions of the basic types of cement. There are other types for various purposes such as architectural concrete and masonry cements, just to name two examples. Your ready mix company will know what the requirements are for your area and for your particular use.
What is Type 4 Portland cement used for?
D. Uses of Type IV Portland Cement –
This type of cement is used where the amount and rate of heat generation must be kept to a minimum.This type of cement is used where low heat of hydration is required.
What is a false set of Portland cement?
Efeitos da temperatura e do tempo de armazenamento no comportamento de falsa pega do cimento Portland CPI-S – R.M. Mota A.S. Silva V.H.S. Ramos J.C.T. Rezende E. de Jesus About the authors The false setting is when cement stiffens prematurely in a few minutes after adding water. Some variables could cause false setting in CPI-S-32 Portland cement, for example, alkali concentration in the cement, the formation of alite (C 3 S) with low reactivity, and cement storage temperature and time in silos.
- Temperature increases cause calcium sulfate dihydrate to dehydrate, forming hemihydrate (CaSO 4,0.5H 2 O) or anhydrite (CaSO 4 ), which causes the false setting.
- In this study, the influence of cement storage temperature (100, 105, 110, 120, and 130 °C) combined with the cement storage time (30, 60, and 120 min) in a silo was studied regarding the CPI-S-32 false setting behavior.
It was verified that temperatures above 110 °C and storage time above 60 min are conditions that favor the false setting of CPI-S-32 cement. Physicochemical analysis, TG/DTG, XRF, and XRD were applied as complementary analyzes for the false setting assays of CPI-S-32.
Keywords: false setting; CPI-S-32 Portland cement; cement storage temperature; cement storage time Falsa pega é a denominação dada ao enrijecimento prematuro anormal do cimento em poucos minutos após a adição de água. Alguns fatores podem ocasionar falsa pega no cimento Portland CPI-S-32, por exemplo, concentração de álcalis no cimento, formação de alita (C 3 S) com baixa reatividade e temperatura e tempo de armazenamento do cimento nos silos.
O aumento da temperatura causa a desidratação do sulfato de cálcio di-hidratado formando o hemi-hidrato (CaSO 4,0,5H 2 O) ou anidrita (CaSO 4 ), que causa a falsa pega. Assim, neste trabalho foi avaliada a influência da temperatura de armazenamento do clínquer (100, 105, 110, 120 e 130 °C) combinada com o tempo de armazenamento do cimento (30, 60 e 120 min) no comportamento de falsa pega do CPI-S-32.
- Foi verificado que temperatura de armazenamento acima de 110 °C e tempo de armazenamento acima de 60 min são condições que favorecem a falsa pega do cimento CPI-S-32.
- Análises físico-químicas, TG/DTG, FRX e DRX foram utilizadas como análises complementares aos ensaios de falsa pega do CPI-S-32.
- Palavras-chave: falsa pega; cimento Portland CPI-S-32; temperatura de armazenamento; tempo de armazenamento The population growth, as a rule, causes an increase in materials used for housing construction 1 1 E.I.
El-Shafey, S.N.F. Ali, S. Al-Busai, H.A.J. Al-Lawati, J. Environ. Chem. Eng.4 (2016) 2713., and cement can be highlighted among these materials. Cement can be defined as a material with adhesive and cohesive properties, which make it able to join mineral fragments in the form of a compact unit 2 2 J.P.
- Lopes, T. Rudnick, C.H.
- Martins, Rev. Eletr. Eng.
- Civil 14 (2018) 216.
- Portland cement is a hydraulic binder obtained by grinding a Portland clinker with the addition of one or two forms of calcium sulfate during the production process.
- Portland cement CPI-S-32 is composed of 6% to 10% (m/m) of carbonate material containing at least 75% CaCO 3 3 3 ABNT NBR 16697, “Cimento Portland: requisitos”, Ass.
Bras. Norm. Técn., Rio Janeiro (2018). processed by milling 4 4 R. Pilar, R.A. Schankoski, A.J. Dal Moro, W.L. Repette, Matéria 21 (2016) 92.), ( 5 5 S. Demirhan, K. Turk, K. Ulugerger, Constr. Build. Mater.196 (2019) 115.), ( 6 6 W.P. Gonçalves, V.J. Silva, J. Gomes, R.R.
- Menezes, G.A.
- Neves, H.C.
- Ferreira, L.N.L.
- Santana, Cerâmica 60, 355 (2014) 316.
- During the cement milling and storage stages, operational parameters must be controlled according to NBR 16697 standard.
- Among these parameters, the cement storage temperature may cause an alteration in the physical-chemical behavior of cement, such as the anomalous behavior of a false setting.
Gypsum is added to the clinker in this stage to delay the hydration reaction of tricalcium aluminate (C 3 A), which is the clinker constituent that features the biggest reactivity with water. The reactions in which the CPI-S becomes a binder material occur in the paste, constituted by the direct addition of some water molecules and cement.
- In other words, the presence of water and the silicates and aluminates of cement create hydrated products, which result in a resistant and steady mass over time.
- Among the several hydration products of CPI-S, the hydration reaction of silicates, calcium hydroxide, and aluminates can be highlighted.
- Both calcium silicates, named as tricalcium silicate or alite (C 3 S) and dicalcium silicate or belite (C 2 S), are the main components of cement, with the first experiencing hydration faster than the second 7 7 A.M.
Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman. Porto Alegre (2013) 448. due to higher reaction speed compared to the C 2 S, considering that C-S-H gel is the final complete hydration product of both C 3 S and C 2 S 7 7 A.M. Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman.
Porto Alegre (2013) 448.), ( 8 8 P.K. Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782. Furthermore, both calcium silicates during their hydration form the hydrated calcium silicate (C-S-H), which performs a dominant role in determining the mechanical and physical-chemical properties of the concrete 9 9 E.
Gartner, I. Maruyama, J. Chen, Cem. Concr. Res.97 (2017) 95. The C-S-H normally consists of 50% to 60% of the solid volume in a fully hydrated cement paste, therefore being the most important phase in determining the properties of the paste. Unlike C-S-H, calcium hydroxide has its stoichiometry defined as Ca(OH) 2 and constitutes 20% to 25% of the solid volume in the hydrated cement paste.
However, the C 3 A reaction with water is immediate and creates crystalline hydrates of C 3 AH 6 (tricalcium aluminate hydrate), C 4 AH 19 (hexagonal calcium aluminate hydrate), and C 2 AH 8 (dicalcium aluminate hydrate) with heat release, and occupy around 15% to 20% of the solid volume in a hydrated cement paste 10 10 A.M.
Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912. In the hydration process of CPI-S, both the hydration of C 3 A and its hydration in the presence of gypsum are important, being responsible for slowing down the hydration reaction and the immediate setting of the cement.
This effect can be explained by the fact that when gypsum and alkalis go into solution quickly, the C 3 A solubility is reduced in the presence of hydroxyl, sulfate, and alkalis 8 8 P.K. Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782. The setting refers to the cement paste going from a fluid state to a rigid state where the paste acquires a certain consistency which makes it improper for work, and in which the physicochemical process occurs by means of exothermal reactions.
The initial setting is the start of plasticity loss in the water and cement mixture, followed by the paste temperature rising. The final setting is when the paste ceases to be deformed by a small load and starts to form a rigid block. In addition to the setting, another behavior that is highlighted in CPI-S cement is the false setting, which is when abnormal premature stiffening of the cement occurs a few minutes after adding water.
False setting differs from the instantaneous setting since there is no important heat release 10 10 A.M. Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912. When the cement C 3 A has low reactivity, as is the case of partially hydrated cement or carbonated cement that may have been stored in inappropriate form, and a large amount of gypsum is present in the cement at the same time, the solution will contain a low concentration of aluminate ions, making it rapidly supersaturated with calcium and sulfate ions, leading to the rapid formation of large gypsum crystal with a corresponding loss in the consistency, which therefore causes the false setting of the cement 8 8 P.K.
Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782. Some factors influence the false setting in CPI-S such as cement alkalis, the activation of C 3 S due to high moisture, the clinker milling temperature, and storage temperature and time of cement in silos.
Partially calcined gypsum (CaSO 4,2H 2 O) loses 75% of its crystallization water, forming a hemihydrate or basanite (CaSO 4,0.5H 2 O) or anhydrite (CaSO 4 ) which possesses five times more solubility than gypsum, and then forms a supersaturated solution when mixed with water which tends to deposit dihydrate crystals.
Moreover, the cement hydrates in needle calcium sulfate form when mixed with water. Thus, a false setting can be named ‘calcium sulfate setting’, resulting in the paste stiffening 7 7 A.M. Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman. Porto Alegre (2013) 448.), ( 8 8 P.K.
Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782.), ( 10 10 A.M. Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912.), ( 11 11 F.L.A Bauer, Materiais de construção, 5 ed., LTC (2000) 471. In a previous study 12 12 S.M.
Pinheiro, “Gesso reciclado: avaliação das propriedades para uso em componentes”, Tese Dout., Unicamp, Campinas (2011) 304., calcium sulfate hemihydrate was the first chemical species of gypsum dehydration, in which the reaction process began at 106 °C.
- In another study 13 13 V.M.
- John, M.A.
- Cincotto, in “Materiais de construção civil”, G.C.
- Isaia (Ed.), Ibracon, S.
- Paulo (2007) 727.
- The occurrence of gypsum dehydration was maximized at temperatures above 125 ºC, which led to the cement presenting false setting behavior.
- An additional factor that must be studied is the storage time of cement in silos.
This can cause a false setting as a result of the cement compacting inside the silo, causing a rise in the temperature of the stored cement and, consequently, dehydration reactions in the CPI-S. There are generally aeration systems in the silos which cause the cement to be in constant movement, preventing the increase in cement temperature.
- This storage period must be sufficient for the cement to lose the necessary heat in the interior of silos before shipping, as this factor can be crucial to the occurrence of problems in the concrete.
- Thus, the objective of the present study is to evaluate the influences of the storage temperature and time of cement on the false setting behavior of CPI-S-32, which is the Portland cement with the highest production volume in the Brazilian market, used in general construction services with no special properties required.
Preparation of raw materials : the clinker used in this study came from the clinkerization process of a cement company located in Capanema-PA (Brazil). First, 55 kg of clinker was processed in a jaw crusher (Pragotec, 3020) for the granulometric reduction of the material.
After crushing, clinker grinding was performed using a disc mill (Renard, MSA 200-4472) until all the material reached a particle size that was able to pass through a 170-mesh sieve (NBR 14656). The homogenization was performed in a mechanical mixer (Pragotec, Type V) with three volumetric chambers. This stage was necessary to ensure the clinker samples had uniformity.
The gypsum was supplied by a cement company located in Capanema-PA (Brazil). The raw material was initially placed in an oven (Fanem, 313/SE) at 55±5 °C for 10 h. After this treatment, 8.0 kg of gypsum was milled in the disc mill until all the material reached between 1.0% and 3.5% of material retained in a 325-mesh sieve.
- Next, homogenization was performed in a plastic bag and stored in the plastic bag itself.
- The limestone was provided by a cement company located in Capanema-PA (Brazil).
- The material was initially dried in the oven at 110±10 °C for 2 h.
- Next, 8.0 kg of this material was ground in the disc mill until all the material presented a particle size passing through a 170-mesh sieve.
Next, the homogenization was performed in a plastic bag and then stored. Preparation of CPI-S-32 cement : CPI-S-32 was prepared by mixing 88.5% clinker, 5.5% gypsum, and 6.0% limestone (mass percent) using a ball mill (Pragotec, 1A). The milling operation produced a material with 4.0% to 6.5% of granulometry retained in a 325-mesh sieve.
Lastly, homogenization was performed in a plastic bag. Influence of storage temperature and time : samples containing 3.0 kg of CPI-S-32 were stored in the oven at different temperatures (100, 105, 110, 120 and 130 ºC) and different times (30, 60 and 120 min) inside metal containers with a height of 52 mm and diameter of 304 mm (simulating the storage in a silo), according to Table I,
The samples were stored at atmospheric pressure (1 atm). Table I Experimental conditions of the CPI-S-32 sample production. Tabela I Condições experimentais de produção das amostras de CPI-S-32. Determination of the CPI-S-32 false setting : determination of false setting was performed in accordance with the ASTM C451-13 standard 14 14 ASTM C451-13, “Standard test method for early stiffening of hydraulic cement (paste method)”, Am.
- Soc. Test. Mater. (2013).
- The CPI-S-32 paste preparation was performed in a room at 23±2 ºC and relative humidity higher than 50%, with 350.0±0.1 g of CPI-S-32 cement and 122.5±0.1 g of distilled water.
- The water-cement CPI-S-32 paste was prepared in a stainless vat, and the mixing was performed with the aid of a spreader for 1.5 min.
Vicat apparatus (Solotest, 1.111.001) was used to determine the false setting. The paste had no false setting when the Tetmajer probe of the Vicat equipment reached a value ≥33 mm of the base plate after 30 s, starting from the instant it was released.
- Characterization of materials : the raw materials and CPI-S-32 were characterized according to NBR 14656 standard 15 15 ABNT NBR 14656, “Cimento Portland e matérias-primas: análise química por espectrometria de raios X, método de ensaio”, Ass. Bras. Norm.
- Técn., Rio Janeiro (2001).
- X-ray fluorescence spectroscopy (XRF) was performed with a spectrometer (Oxford Instr., X-Supreme8000) with incident radiation energy of 10 keV.
Cast pellets were produced in a Vulcan Fusion machine (FluXana, 2M). Pressed pellets for the gypsum and CPI-S-32 samples were made in a hydraulic press (Carver, 3853-0), at a pressure of 15.0 kgf/cm 2, The analyzes performed in the physicochemical characterization of CPI-S-32 were loss on ignition (LOI) 16 16 ABNT NBR NM 18, “Cimento Portland: análise química, determinação de perda ao fogo”, Ass.
- Bras. Norm.
- Técn., Rio Janeiro (2012).), ( 17 17 R.R.
- Menezes, M.M.
- Ávila Júnior, L.N.L.
- Santana, G.A.
- Neves, H.C.
- Ferreira, Cerâmica 54, 330 (2008) 152.), ( 18 18 M.G.
- Silva-Valenzuela, M.M.
- Chambi-Peralta, I.J.
- Sayeg, F.M.
- De Souza Carvalho, S.H.
- Wang, F.R.
- Valenzuela-Díaz, Appl.
- Clay Sci.155 (2018) 111.), ( 19 19 S.H.
Ngo, T.P. Huynh, T.T.T. Le, N.H.T. Mai, IOP Conf. Ser. Mater. Sci. Eng.371 (2018) 12007., insoluble residue 20 20 ABNT NBR NM 15, “Cimento Portland: análise química, determinação de resíduo insolúvel”, Ass. Bras. Norm. Técn., Rio Janeiro (2012)., magnesium oxide and sulfur trioxide contents, specific mass 21 21 ABNT NBR 16605, “Cimento Portland e outros materiais em pó: determinação da massa específica”, Ass.
Bras. Norm. Técn., Rio Janeiro (2017)., retention index with a 75 µm sieve 22 22 ABNT NBR 12826, “Cimento Portland e outros materiais em pó: determinação do índice de finura por meio de peneirador aerodinâmico”, Ass. Bras. Norm. Técn., Rio Janeiro (2014)., normal paste consistency 23 23 ABNT NBR 16606, “Cimento Portland: determinação da pasta de consistência normal”, Ass.
Bras. Norm. Técn., Rio Janeiro (2017)., initial and final setting time 24 24 ABNT NBR 16607, “Cimento Portland: determinação dos tempos de pega”, Ass. Bras. Norm. Técn., Rio Janeiro (2017)., Le-Chatelier’s heat expansion 25 25 ABNT NBR 11582, “Cimento Portland: determinação da expansibilidade de Le Chatelier”, Ass.
- Bras. Norm.
- Técn., Rio Janeiro (2016).
- And specific area 26 26 ABNT NBR 16372, “Cimento Portland e outros materiais em pó: determinação da finura pelo método de permeabilidade ao ar (método de Blaine)”, Ass. Bras. Norm.
- Técn., Rio Janeiro (2015).
- After different cement storage temperatures and times in a silo.
By the X-ray diffraction (XRD) analysis, the crystalline phases of the CPI-S-32 cement samples were identified employing a diffractometer (Bruker, D8 Advance) with CuKα radiation, 40 kV voltage, 40 mA current, 2θ range from 2° to 65°, a scan speed of 1 °.min -1, step width of 0.02°, and time step of 0.2 s.
- The mineral crystalline phases were identified using the MATCH! analysis program, in which the ICSD (Inorganic Crystal Structure Database) crystallographic files were inserted 27 27 A.C.S.
- Alcântara, M.S.S.
- Beltrão, H.A.
- Oliveira, I.F.
- Gimenez, L.S.
- Barreto, Appl.
- Clay Sci.39 (2008) 160.), ( 28 28 C.P.
- Santos, H.A.
Oliveira, R.M.P.B. Oliveira, Z.S. Macedo, Cerâmica 62, 362 (2016) 147. The thermogravimetry/derivative thermogravimetry (TG/DTG) of CPI-S-32 was performed in a thermal analyzer (Netzsch, STA 449 F1 Jupiter) using an aluminum crucible and a flow rate of 100 mL.min -1 of N 2 from 25 to 1200 °C using a heating rate of 10 °C.min -1,
The CPI-S-32 samples in powder form were dispersed on a carbon tape and coated with a thin layer of gold in a metallizer (Kurt J Lesker, 108) and then analyzed using a scanning electron microscope (SEM, Jeol, JJSM-6510LV). The loss on ignition and compositions of raw materials in terms of oxides used in the preparation of CPI-S-32 samples are shown in Table II,
The low loss on ignition value of clinker was due to the decomposition of all organic material and volatiles of the mixture of limestone, clay, and correctives during the clinkerization process. In contrast to the clinker, the limestone showed a higher loss on ignition value combined with the presence of a significant quantity of CO 2 in its composition.
As loss on ignition is a chemical requisite established by NBR 16697 standard for CPI-S-32, the added quantity of limestone is limited due to its high values of loss on ignition. As observed in the clinker, the calcium and silicon oxides were the main constituents, corresponding to an amount higher than 80.0% of the chemical composition, proving that clinker is a product that is mostly composed of calcium silicates 3 3 ABNT NBR 16697, “Cimento Portland: requisitos”, Ass.
Bras. Norm. Técn., Rio Janeiro (2018). For gypsum, the presence of the main components calcium oxide and sulfur trioxide was observed ( Table II ) with percentages of 32.90% and 40.29%, respectively. The presence of these compounds related to the chemical composition of calcium sulfate was much higher than the other oxides present in the gypsum composition.
According to the literature 29 29 K.K.S. Melo, A.P.C. Lima, M.C. Santana, V.C.P. Andrade, A.L.C. Braga, K.V. Correia, Holos 6 (2017) 194., the mean stoichiometric composition of gypsum is around 32.0% CaO and 45.0% SO 3, A predominance of calcium oxide is observed in the limestone composition with a content higher than 45.0%.
The limestone added to the mixture of clinker and gypsum for the production of CPI-S-32 contained 85.7% CaCO 3, which constituted a value higher than 75% established by NBR 16697 as a condition to add carbonate materials. Table II Loss on ignition (LOI) and chemical composition of raw materials by XRF (wt%).
- Tabela II Perda ao fogo (LOI) e composição química das matérias-primas por FRX (% em massa).
- Table III shows the result of the percentage of CPI-S-32 retained in the 75 µm sieve, a procedure performed before determining the CPI-S false setting.
- It was noted that the evaluated granulometry was below the limit established by NBR 16697 and equal to 0.50% retained in the 75 µm sieve.
Table IV presents the false setting values for the CPI-S-32 cement samples. It was verified that the storage temperature and time of the cement in the silo influenced the false setting behavior of the cement. It was verified that CPI-S-32 samples were falsely adjusted for cement storage temperatures above 110 °C and silo storage time over 60 min due to gypsum dehydration reactions and hemihydrate formation above 106 °C 12 12 S.M.
Pinheiro, “Gesso reciclado: avaliação das propriedades para uso em componentes”, Tese Dout., Unicamp, Campinas (2011) 304. It was also observed that the CPI-S-32 presented a false setting of 29 mm when the storage temperature was 110 °C and the cement storage time was 60 min, which represented a much higher value when compared to the CPI-S-32 samples that presented no false setting.
There was a transition stage in these specific experimental conditions where there was a need for a deeper investigation in terms of dehydration kinetics to more accurately verify the onset on the loss of plasticity in the CPI-S until its premature stiffness.
Table III Fineness of CPI-S-32 retained in the 75 µm sieve. Tabela III Finura do CPI-S-32 retido na peneira de 75 µm. Table IV False setting values obtained for CPI-S-32 at different experimental conditions. Tabela IV Valores obtidos de falsa pega do CPI-S-32 para diferentes condições experimentais. After suffering a dehydration process, the gypsum (calcium sulfate dihydrate) contained in the clinker mixture forms calcium sulfate hemihydrate between its products, which deposits dihydrate crystals due to having a higher solubility than gypsum, thereby causing the paste to stiffen 7 7 A.M.
Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman. Porto Alegre (2013) 448.), ( 8 8 P.K. Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782.), ( 11 11 F.L.A Bauer, Materiais de construção, 5 ed., LTC (2000) 471.
This result was confirmed by the XRD analyses, which showed that the cement with false setting behavior lost the characteristic gypsum peak when compared to the cement that did not show a false setting. The CPI-S-32 storage time in the silo only influences the false setting of the CPI-S-32 if combined with any factor that may cause an anomaly in the cement.
Table IV shows that the false adjustment occurred in all CPI-S-32 samples for storage time above 60 min and temperatures above 110 °C. This occurred due to the compaction effect of the cement inside the silo since the temperature of cement grains rises, causing advanced stiffening of the cement paste.
However, it was also observed that the cement samples in the studied temperatures did not show false setting behavior for storage periods close to 30 min, from which it was inferred that there was not enough time for the stored cement to suffer a compaction process and consequently an increase in the grain temperature, and thus the false setting was not possible.
The results obtained for the chemical requirements of loss on ignition and insoluble residue of the CPI-S-32 samples for all storage temperature range and storage time in a silo are shown in Table V, All the produced CPI-S-32 samples presented loss on ignition values below 6.5%, which is the limit established by NBR 16697.
- It was also noticed that the loss on ignition values did not have a major change when comparing the six samples presenting a false setting to those which did not.
- Thus, the mass loss of the cement after heating in a furnace around 1000 °C was maintained stable for all the storage temperature and time ranges in a silo.
Also, the insoluble residue calculated for all conditions showed values less than 3.5%, which is the limit established by NBR 16697. This showed that the false setting phenomena of the studied CPI-S-32 samples did not influence the chemical properties of the insoluble residue.
- Table V Loass on ignition and insoluble residue values of CPI-S.
- Tabela V Valores de perda ao fogo e resíduo insolúvel do CPI-S-32.
- Table VI shows the obtained results for the physical requisites of the specific mass, normal paste consistency, initial and final setting time, heat expansion, and specific area for both the CPI-S-32 samples, which presented false setting behavior as compared to the ones which did not.
It was possible to verify that the specific mass of the cement samples which presented false setting behavior was similar to the samples which did not show alteration. Although it is an optional requisite, its determination is fundamental to calculate the specific area of CPI-S samples.
- A normal paste consistency was obtained with enough water to provide a standardized pattern.
- The test value is presented in terms of water/cement mass ratio, which indicated how much water the CPI-S demanded to produce a workable concrete.
- According to the results, a slight percentage increase of water was needed to produce a workable paste with the increase in both the CPI-S-32 storage temperature and time in the silo.
This is probably justified on the dehydration process suffered by the calcium sulfate dehydrated 8 8 P.K. Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782.), ( 10 10 A.M. Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912.
- As proven by the XRD analyses of the CPI-S cement 130.120 when compared to CPI-S 100.30.
- The determination of normal paste consistency identified the necessary quantity of water to be added to the cement for the determination tests of initial and final setting time, constituting a normative physical requisite for CPI-S production.
Table VI Physical requirements of specific mass, normal consistency, initial and final setting times, heat expansion, and specific area of CPI-S-32. Tabela VI Requisitos físicos de massa específica, consistência normal, tempo de início e fim de pega, expansibilidade a quente e área específica das amostras de CPI-S-32.
In evaluating the setting times, all the CPI-S-32 samples presented an initial setting time longer than 1 h, which is the limit established by NBR 16697 as the physical demand in CPI-S-32 production and a final setting time less than 10 h. The results showed that all samples which presented false setting behavior had more difficulties for plasticity loss of the water and cement mixture, which meant longer times of setting, showing that the increase in temperature caused an increase in the initial and final setting time of this cement 7 7 A.M.
Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman. Porto Alegre (2013) 448.), ( 10 10 A.M. Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912. All CPI-S-32 samples exhibited Le-Chatelier heat expansion values less than 5.0 mm, which is the limit imposed by NBR 16697.
- This meant that all CPI-S-32 samples did not present volumetric variation due to the hydration process of cement 3 3 ABNT NBR 16697, “Cimento Portland: requisitos”, Ass. Bras. Norm.
- Técn., Rio Janeiro (2018).), ( 7 7 A.M.
- Neville, J.J.
- Brooks, Tecnologia do concreto, 2 ed., Bookman.
- Porto Alegre (2013) 448.
It was noted that the specific area of the samples of CPI-S cement presented values with low variation, both for samples that presented false setting and those that not. The specific area had a direct relationship with the cement granulometry due to the grains presenting in its composition; moreover, the CPI-S samples were prepared with the same granulometry (retained material in 75 μm sieve), justifying the obtained results.
- Table VII presents the chemical constituents of the CPI-S-32 samples.
- The calcium and silicon oxides were the major constituents in the studied samples and together were responsible for the hydration reactions of silicates, corresponding to more than 60% of volume in the cement reactions 6 6 W.P.
- Gonçalves, V.J.
Silva, J. Gomes, R.R. Menezes, G.A. Neves, H.C. Ferreira, L.N.L. Santana, Cerâmica 60, 355 (2014) 316. The variation of the calcium and silicon elements in the cement directly interferes in the C 3 S and C 2 S anhydrous phases, in which a higher concentration of calcium leads to a preponderant production of alite, and is the main element responsible for the hydrated C-S-H and Ca(OH) 2 phases 30 30 L.
- Simão, N.J. Lóh, D. Hotza, F.
- Raupp-Pereira, J.A.
- Labrincha, O.R.K.
- Montedo, Cerâmica 64, 371 (2018) 311.), ( 31 31 J.E.F.
- Nascimento, A.C.V.
- Nóbrega, H.C.
- Ferreira, G.A.
- Neves, L.N.L.
- Santana, Cerâmica 65, 373 (2019) 85.
- The aluminum and iron oxides are no less important, being responsible for aluminate reactions and corresponding to 20% of the volume of the reactions which occur in the cement.
The oxide percentages were not influenced by the false setting phenomena of the CPI-S-32 samples. The magnesium oxide and sulfur trioxide were below the values required by NBR 16697, being lower than 6.5% and 4.5%, respectively. The low MgO content makes the CPI-S-32 normally self-hydratable and loses the capacity to cause cracks by expanding inside the already hardened concrete.
- Likewise, low values of SO 3 originated from the gypsum decreases the possibility of interference in the initial strength of the cement, as shown by theoretical studies 10 10 A.M.
- Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912.
- Table VII Chemical composition of CPI-S-32 samples by XRF (wt%).
Tabela VII Composição química das amostras de CPI-S-32 por FRX (% em massa). X-ray diffraction ( Fig.1 ) and TG/DTG analyses ( Fig.2 ) were performed on two CPI-S-32 samples, sample CPI-S-32 130.120, which presented false setting, and CPI-S-32 100.30 sample, which did not show false setting.
It was possible to note the presence of the main crystalline compounds in both samples as alite (C 3 S), belite (C 2 S), tricalcium aluminate (C 3 A), tetracalcium ferroaluminate (C4AF), and calcite (CaCO 3 ) 32 32 R.C.O. Romano, A.L. Fujii, R.B. Souza, M.S. Takeashi, R.G. Pileggi, M.A. Cincotto, Cerâmica 62, 363 (2016) 215.), ( 33 33 P.C.
Aïtcin, R.J. Flatt, Science and technology of concrete admixtures, Woodhead Publ. (2016) 666.), ( 34 34 T.R.S. Nobre, T.A. Santos, R.A. Argolo, Ribeiro, D.V. Ribeiro, in VIII Enc. Cient. Fís. Apl., Blucher Proc. (2017) 49.), ( 35 35 E.G.A. Ferreira, F. Yokaichiya, J.T.
- Marumo, R.
- Vicente, F.
- Garcia-Moreno, P.H. Kammc, M. Klaus, M.
- Russina, G.
- Gunther, C.E.
- Jimenez, M.K.K.D.
- Franco, Physica B Condens.
- Matter 551 (2018) 256.), ( 36 36 W.H.
- Duda, Manual tecnológico del cemento, Edit. Técn.
- Asoc., Barcelona (1977) 332.), ( 37 37 M.C.G.
- Juenger, F.
- Winnefeld, J.L.
- Provis, J.H.
- Ideker, Cem.
Concr. Res.41 (2011) 1232.), ( 38 38 O. Labahn, Prontuario del cemento, 5 ed., Edit. Técn. Asoc., Barcelona (1985) 1016.), ( 39 39 H.F.W. Taylor, Cement chemistry, 2 ed., Thomas Telford, London (1997) 102. In addition to these compounds, the presence of gypsum (CaSO 4,2H 2 O) was observed in the CPI-S-32 100.30 sample at 11.6° and 20.8° (2θ).
- Also, the disappearance of dihydrated calcium sulfate peaks was observed in the CPI-S-32 130.120 sample, since the gypsum was consumed by dehydration process forming basanite (CaSO 4,0.5H 2 O).
- As this compound is about 5 times more soluble than gypsum, it allowed the formation of a supersaturated solution that tended to deposit dihydrate crystals, which caused early stiffness in the mass of CPI-S-32 130.120, characterizing the false setting in this studied sample 7 7 A.M.
Neville, J.J. Brooks, Tecnologia do concreto, 2 ed., Bookman. Porto Alegre (2013) 448.), ( 8 8 P.K. Mehta, P.J.M. Monteiro, Concreto: microestrutura, propriedades e materiais, 2 ed., IBRACON, S. Paulo (2014) 782.), ( 10 10 A.M. Neville, Propriedades do concreto, 5 ed., Bookman, Porto Alegre (2016) 912.)- ( 12 12 S.M.
Pinheiro, “Gesso reciclado: avaliação das propriedades para uso em componentes”, Tese Dout., Unicamp, Campinas (2011) 304. Figure 1 X-ray diffraction patterns of CPI-S-32 100.30 (a) and CPI-S-32 130.120 (b) samples. C3: alite; C2: belite; CA: tricalcium aluminate; C: calcite; B: brownmilerite; G: gypsum; Pe: periclase; He: hematite.
Figura 1 Difratogramas de raios X das amostras CPI-S-32 100.30 (a) e CPI-S-32 130.120 (b). C3: alita; C2: belita; CA: aluminato tricálcico; C: calcita; B: brownmilerita; G: gipsita; Pe: periclásio; He: hematite. Figure 2 TG (a) and DTG (b) curves of the CPI-S-32 100.30 (A) and CPI-S-32 130.120 (B) cement samples.
Figura 2 Curvas de TG (a) e DTG (b) das amostras CPI-S-32 100.30 (A) e CPI-S-32 130.120 (B). The results of thermogravimetric analysis (TG/DTG) for the CPI-S-32 100.30 and CPI-S-32 130.120 samples are presented in Fig.2, The CPI-S-32 samples presented continuous mass loss with lower or larger loss rates in the analyzed temperature range.
The thermograms of the CPI-S-32 100.30 and CPI-S-32 130.120 samples showed the decomposition in three stages. The first occurred between 30 and 180 °C, with the highest band maximum identified by the DTG at 130 °C being attributed to water loss from the dehydration of calcium sulfate dihydrate, equivalent to 1.3% for CPI-S-32 100.30 and 0.2% for CPI-S-32 130.120.
- Between 180 and 500 °C, the highest band value at 440 °C was observed with a mass loss of 0.7% for CPI-S-32 100.30 and 0.6% for CPI-S-32 130.120, corresponding to dehydration of calcium hydroxide 40 40 J.
- Hoppe Filho, A. Gobbi, E.
- Pereira, R.S.
- Tanaka, M.H.F.
- Medeiros, Matéria 22 (2017) 18.
- Then between 500 and 800 °C, at the highest band maximum at 730 °C, mass losses of 3.2% for CPI-S-32 100.30 and 3.4% for CPI-S-32 130.120 were observed due to the loss of CO 2 by decomposition of calcium carbonate.
Thus, the total mass loss was 5.2% for CPI-S-32 100.30 and 4.2% for CPI-S-32 130.120. Accordingly, it was verified that the mass loss of the CPI-S 100.30 sample was higher than CPI-S 130.120 because of the higher dehydration mass loss of calcium sulfate dehydrate.
It was observed that the decomposition band of dehydrated calcium sulfate of the CPI-S 130.120 cement was smaller than that of the CPI-S 100.30 cement, probably due to the partial or total decomposition of dehydrated calcium sulfate added during the storage, which can transform into hemihydrate calcium sulfate.
Analyzing Fig.3, it was noted that the sample CPI-S-32 130.120 had a uniform morphology and little porosity, compared to the sample CPI-S-32 100.30, which can be attributed to the interaction temperature and time used. Probably this little porosity made it difficult to hydrate the constituents of the cement, which may have led to a false setting.
Figure 3 SEM micrographs of the samples CPI-S-32 100.30 (a) and CPI-S-32 130.120 (b). Figura 3 Micrografias de MEV das amostras CPI-S-32 100.30 (a) e CPI-S-32 130.120 (b). Based on the performed tests and analyses, it was concluded that the storage temperature above 110 °C and the storage time of CPI-S-32 above 60 min influenced the false setting behavior of cement.
Six of 15 samples of analyzed cement showed this anomaly, with the cement paste stiffening instantaneously without the release of characteristic heat. The false setting did not influence the parameters of loss on ignition, insoluble residue, fineness retained in the 75 µm sieve, MgO and SO 3 content, initial and final setting time, heat expansion, specific mass, specific area, and normal paste consistency as established by NBR 16697 standard.
X-ray diffraction analysis showed in a cement sample with false setting behavior (CPI-S-32 130.120 – stored at 130 °C and 120 min) the absence of CaSO 4,2H 2 O phase, since the gypsum was consumed by the dehydration process during the storage stage and transformed into CaSO 4,0.5H 2 O, differently from that observed in a sample that did not show false setting (CPI-S-32 100.30 – stored at 100 °C and 30 min) in which the gypsum was present.
This was confirmed by thermogravimetric analysis that showed a higher mass loss of the CPI-S-32 100.30 cement sample (5.2%) than the CPI-S-32 130.120 cement (4.2%), which the difference mainly occurred between 30 and 180 ºC when water loss from the dehydration of the calcium sulfate dihydrate occurred.
In the other temperature ranges, the mass losses by calcium hydroxide dehydration and due to the loss of CO 2 by decomposition of calcium carbonate were similar. The results showed the optimal operating conditions of the storage temperature and time of the cement in order to avoid false setting and a loss in the CPI-S-32 product quality.
It was identified that the CPI-S-32 could present a false setting in the storage temperature range of 110 to 130 ºC combined with storage time from 60 to 120 min, which causes financial loss to the industry. As a false setting is a specific quality parameter, mainly for CPI-S-32 cement, its control is necessary to attend the consumers.
Higher consumption of energy and raw materials can be avoided by knowing that the temperature and the storage time of the cement in silos are variables that need to be controlled by the cement industry. The authors are grateful to CAPES, FAPITEC-SE, the Federal University of Sergipe, the Laboratory of Industrial Chemistry, and LMDCEM/UFS for their support in the accomplishment and participation of the obtained results.
To the cement industry located in Capanema-PA, for the supply of clinker, gypsum, and limestone and support in carrying out the experimental activities.
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Publication in this collection 17 July 2020 Date of issue Jul-Sep 2020
Received 13 Dec 2019 Reviewed 08 Feb 2020 Reviewed 06 Apr 2020 Accepted 09 Apr 2020
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What are the three ingredients used to make portland cement?
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.
What is the composition of portland cement Class 11?
Portland cement consists compounds of lime (calcium oxide, CaO) mixed with silica (silicon dioxide, SiO2) and alumina (aluminum oxide, Al2O3). The lime is obtained from a calcareous (lime-containing) raw material, and the other oxides are derived from an argillaceous (clayey) material.
What are 3 common raw materials to manufacture portland cement?
Chemical Composition of Portland Cements – The raw material that is used in the manufacturing of Portland cement mainly consists of lime, silica, alumina and iron oxide. In the cement, the oxide content is about 90%. The oxide composition of ordinary Portland cement is given below: During the heating of raw material in the kiln, the oxides interact with each other and forms more complex compounds. The Portland cement consists of 4 basic chemical compounds. These four compounds are given in the table below:
What is the main ingredient in ordinary portland cement?
The important ingredients present in Portland Cement are dicalcium silicate (Ca2SiO4)) (26%), tricalcium silicate (Ca3SiO5)) (51%), tricalcium aluminate (Ca3Al2O6)) (11%).