Concept: The four major compounds which are constituents of cement are: a) Tricalcium silicate (C 3 S): 3CaO.SiO 2 b) Dicalcium silicate (C 2 S): 2CaO.SiO 2 c) Tricalcium Aluminate (C 3 A): 3CaO.Al 2 O 3 d) Tetra-calcium Alumino Ferrite (C 4 AF): 4CaO.Al 2,Fe 2 O 3 These compounds are also known as Bogue Compounds,
C 3 S readily reacts with water, produces more heat of hydration and is responsible for the early strength of concrete. C 2 S hydrates more slowly and produce less heat of hydration and are responsible for later strength of concrete.
1. Tricalcium Silicate C 3 S – (25 – 50%) – Normally 40%
It is considered as the best cementing material and is well-burnt cement. It hydrates rapidly generating high heat and develops an early hardness and strength. Raising of C 3 S content beyond the specified limits increases heat of hydration and solubility of cement in water. The heat of hydration is 500 J/g,
2. Dicalcium Silicate (C 2 S) – (25 – 40%) – (Normally 32%)
It hydrates and hardens slowly and takes a long time to add to the strength (after a year or more) i.e. it is responsible for ultimate strength, It imparts resistance to chemical attack. Raising of C 2 S content renders clinkers harder to grind, reduces early strength, decreases resistance to freezing and thawing at an early age and decreases heat of hydration. At an early age, less than a month, C 2 S has little influence on strength and hardness. While after one year, its contribution to the strength and hardness is proportionately almost equal to C 3 S. The heat of hydration is 260 J/g.
3. Tricalcium Aluminate (C 3 A) – (5 – 11%) -(Normally 10.5%).
It rapidly reacts with water and is responsible for the flash set of finely grounded clinkers. The rapidity of action is regulated by the addition of 2-3% of gypsum at the time of grinding the cement. It is most responsible for the initial setting, the high heat of hydration and has a greater tendency to volume changes causing cracking. Raising the C 3 A content reduces the setting time, weakens resistance to sulphate attack and lowers the ultimate strength, heat of hydration and contraction during air hardening. The heat of hydration of 865 J/g.
4. Tetracalcium Alumino Ferrite – (C 4 AF 8 – 14%) (Normally 9%)
It is responsible for the flash set but generates less heat. It has the poorest cementing value. Raising C 4 AF content reduces the strength slightly. The heat of hydration 420 J/g,
The rate of heat evolution of the principal compound if equal amount of each is considered will be in following descending order: C 3 A (865 J/g) > C 3 S (500 J/g) > C 4 AF (420 J/g) > C 2 S (260 J/g), Thus by increasing the C 2 S content the heat of hydration decreases, Note: The development of strength of the four principal compounds of cement with age: The rate of hydration is increased by an increase in the fineness of the cement. However total heat evolved is the same. The rate of hydration of the principal compounds is shown in the figure and will be in the following descending order: C 4 AF > C 3 A > C 3 S > C 2 S Important Points Hydration products of C 2 S are considered better than that of C 3 S. It is because of the lesser time formation of lime when C 2 S hydrates than those in hydration of C 3 S.2C 3 S + 6H → C 3 S 2 H 3 + 3 Ca(OH) 2 2C 2 S + 4H → C 3 S 2 H 3 + Ca(OH) 2 Last updated on Sep 22, 2022 The Chhattisgarh Public Service Commission (CGPSC) has activated the link to submit any objection against the CGPSC AE (Assistant Engineers) Provisional Answer Key.
Contents
- 1 Which cement compound liberates lot of heat during early stage?
- 2 Which compound has highest hydration energy?
- 3 What is the heat of hydration of cement?
- 4 Which has more hydration energy nacl or KCL?
- 5 Which one of the following is highly hydrated?
- 6 Which ion liberates the most hydration energy?
Which compound produces highest heat of hydration in cement?
Discussion :: Concrete Technology – Section 3 ( Q.No.) –
| 123 said: (Jan 18, 2015) | |
| C3A generates 320cal/g heat of hydration which is highest. Also it reacts fast with water. |
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Civil Engineering – Concrete Technology – Discussion
Which constituent contribute high in heat of hydration?
Heat of hydration is most influenced by the proportion of C 3 S and C 3 A in the cement, but is also influenced by water-cement ratio, fineness and curing temperature. As each one of these factors is increased, heat of hydration increases.
Which cement compound liberates lot of heat during early stage?
Discussion :: Building Materials – Section 3 ( Q.No.2 ) –
| PRITHVI said: (May 30, 2014) | |
| Early gain of strength is caused due to tricalcium silicate and thus setting time too. |
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Civil Engineering – Building Materials – Discussion
What are the compounds that contribute much to the hydration of cement?
Background – Concrete is made by the combination of cement, water, and aggregate of various sizes to make a workable slurry that has the consistency of a thick milk shake.
| Name | Percent by Weight | Chemical Formula |
| Tricalcium silicate | 50% | 3Ca0 SiO2 |
| Dicalcium silicate | 25% | 2Ca0 SiO2 |
| Tricalcium aluminate | 10% | 3Ca0 Al2 O3 |
| Tetracalcium aluminoferrite | 10% | 4Ca0 Al2 Fe2 O3 |
| Gypsum | 5% | CaSO4 H2O |
The binding quality of portland cement paste is due to the chemical reaction between the cement and water, called hydration. Portland cement is not a simple chemical compound, it is a mixture of many compounds. Four of these make up 90% or more of the weight of portland cement: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.
In addition to these major compounds, several other play important roles in the hydration process. Different types of cement contain the same four major compounds, but in different proportions. The cement in concrete needs water to hydrate and harden. Even though the chemical reactions may be complete at the surface of the concrete, the chemical reactions at the interior of the concrete take much longer to complete.
The strength of the concrete keeps growing as long as the chemical reactions continue. When water is added to cement, the chemical reaction called hydration takes place and contributes to the final concrete product. The calcium silicates contribute most to the strength of concrete.
- Tricalcium silicates are responsible for most of the early strength (first seven days).
- The original dicalcium silicate hydrates, which form more slowly, contribute to the strength of concrete at later stages.
- The following word equations describe the production of concrete.
- Tricalcium silicate + Water (yields) Calcium silicate hydrate + Calcium hydroxide + heat Dicalcium silicate + Water (yields) Calcium silicate hydrate + Calcium hydroxide + heat Of the five chemical reactions important for providing the strength for concrete the above reactions are the most important.
The two calcium silicates, which constitute about 75 percent of the weight of portland cement, react with water to form two new compounds: calcium hydroxide and calcium silicate hydrate. The latter is by far the most important cementing component in concrete.
- The engineering properties of concrete—setting and hardening, strength and dimensional stability—depend primarily on calcium silicate hydrate gel.
- It is the heart of concrete.
- When concrete sets, its gross volume remains almost unchanged, but hardened concrete contains pores filled with water and air that have no strength.
The strength is in the solid part of the paste, mostly in the calcium silicate hydrate and crystalline phases. The less porous the cement paste, the stronger the concrete. When mixing concrete, therefore, use no more water than is absolutely necessary to make the concrete plastic and workable.
Which compound has highest hydration energy?
Hydration energy increases with an increase in the charge density. So Be2+ has the highest hydration enthalpy.
Which element has maximum hydration energy?
Among the following species, which has the maximum hydration energy? No worries! We‘ve got your back. Try BYJU‘S free classes today! No worries! We‘ve got your back. Try BYJU‘S free classes today! No worries! We‘ve got your back. Try BYJU‘S free classes today! Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses Open in App Suggest Corrections 1 : Among the following species, which has the maximum hydration energy?
Which compound is liberates higher heat?
This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Hydration of Cement”.1. What is hydration of cement? a) Chemical reaction of cement with acid b) Chemical reaction of cement with water c) Chemical reaction of cement with base d) Chemical reaction of cement with salt, and acid View Answer Answer: b Explanation: As water comes into contact with cement particles, hydration reactions immediately starts at the surface of the particles.2.
As the hydration proceeds the deposits of hydrated products on the original cement grains makes the diffusion of water to unhydrated nucleus _ a) Easy b) Very difficult c) Very easy d) Average View Answer Answer: b Explanation: It is difficult thus the rate of hydration decreases with time & as result hydration may take several years.3.
The development of first 28 days strength is on account of the hydration of _ a) C 2 S b) C 3 S c) C 3 A d) C 4 AF View Answer Answer: b Explanation: Higher C 3 S→higher early strength-higher heat generation (roads, cold environments). Higher C S→lower early strength-lower heat generation (dams).4.
Which compound is liberates higher heat? a) C 2 S b) C 3 S c) C 3 A d) C 4 AF View Answer Answer: b Explanation: C3S having a faster rate of reaction accompanied by greater heat generation developes early strength of the paste.5. Which compound is liberates lower heat? a) C 2 S b) C 3 S c) C 3 A d) C 4 AF View Answer Answer: a Explanation: C 2 S hydrates & hardens slowly so results in less heat generation & developes most of the ultimate strength.6.
Which compound may lead to a rapid stiffening of the paste with a large amount of the heat generation? a) C 2 S b) C 3 S c) C 3 A d) C 4 AF View Answer Answer: c Explanation: C 3 A is characteristically fast reacting with water & may lead to a rapid stiffening of the paste with a large amount of the heat generation (Flash-Set)-(Quick-Set).7.
In order to prevent this rapid reaction _ is added to the clinker. a) C 4 AF b) Gypsum c) Water d) Extra cement View Answer Answer: b Explanation: In order to prevent this rapid reaction gypsum is added to the clinker. Gypsum, C3A&water react to form relatively insoluble Calcium-Sulfo-Aluminates. Sanfoundry Global Education & Learning Series – Concrete Technology.
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What does a higher heat of hydration mean?
Heat of hydration is the heat generated when water reacts in contact with the cement powder. The amount of heat released depends on the cement composition, curing temperature, water to cement ratio, and cement fineness. High temperature resulting from heat of hydration may cause thermal cracking of concrete and consequent reduction of mechanical properties.
Which grade of cement has high heat of hydration and why?
Consider the following statements: High Alumina Cement (HAC) 1. has high early compressive strength and high heat of hydration than OPC-43 grade 2. is not suitable to be used in cold regions Which of these statements is/are correct? Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses No worries! We‘ve got your back. Suggest Corrections 0 : Consider the following statements: High Alumina Cement (HAC) 1. has high early compressive strength and high heat of hydration than OPC-43 grade 2. is not suitable to be used in cold regions Which of these statements is/are correct?
What is the heat of hydration of cement?
Hydration of Cement | Heat of Hydration |Stages of Hydration of Cement The hydration of cement is an exothermic reaction that is carried out when cement comes in contact with water. The reaction will result in several by-products that will contribute to the strength of the concrete or mortar formed. Please enable JavaScript
| Fig.1. Hydration Reaction – Changing Microstructure of Cement |
The chemical reaction that takes place between the cement and water is referred to as hydration of the cement. The hydration reaction is an exothermic reaction.The cement hydration will liberate a considerable amount of heat. This is called as Heat of liberation or Heat of Hydration.
- The mixing of cement with water will result in rapid evolution of heat that will last for few minutes.
- This evolution of heat is probably due to the reaction of a solution of aluminates and the sulfates.
- This rapid heat and reaction are depressed by the addition of gypsum.
- The Early heat of hydration is due to the hydration of C3S.
The rate of development of heat is greatly influenced by the fineness of the cement. The normal cement generally produces 89-90J/g in 7 days and 100J/g in 28 days. The hydration process is not instantaneous. The reaction is faster in the early stages and will go decreasing with the time period.
 |
| Table.1: Bogues Compounds |
Hydration is an exothermic process, that will liberate heat through chemical reactions. The process of hydration can be easily followed by monitoring the production of heat that accompanies the reaction. This is done by civic mortar from a batch of concrete and weighing it into a bottle which is placed into an insulated container.
A thermistor is then impeded into the fresh mortar. The output of the thermistor is recorded by the computer. The result is plotted as a curve of temperature v/s the time. The area under the major peak can be related to the early strength development. The five stages involved in the hydration of cement are explained with respect to the figure-2.
There are Five stages of cement hydration:
Initial Hydrolysis Advertisements Induction Period or the Dormant Period Acceleration Deceleration Steady State
- The mixing of cement with water will result in rapid evolution of heat that will last for few minutes.
- This evolution of heat is probably due to the reaction of a solution of aluminates and the sulfates.
- This rapid heat and reaction are depressed by the addition of gypsum.
- The Early heat of hydration is due to the hydration of C3S.
- A thermistor is then impeded into the fresh mortar.
- The output of the thermistor is recorded by the computer.
- The result is plotted as a curve of temperature v/s the time.
- The area under the major peak can be related to the early strength development.
- The five stages involved in the hydration of cement are explained with respect to the figure-2.
- The layer acts as a protective barrier and temporarily delays the dissolution of the particle.
- This slows down the reaction for a period of several hours.
- This is called as the Dormant Period.
- The existence of the dormant period allows the concrete to be transported to the construction site and placed and finished in the forms.
| Fig.2.The Heat of Hydration – Calorimetry curve. |
/ol> Stage 1- Initial Hydrolysis: The initial dissolution of cement will result in the sort release of heat shown by the first peak in the calorimetry curve. Stage 2 – Induction or Dormant Period: After the initial dissolution process, the hydration products are precipitated on the surface of each cement particle.
The layer acts as a protective barrier and temporarily delays the dissolution of the particle. This slows down the reaction for a period of several hours. This is called as the Dormant Period. The existence of the dormant period allows the concrete to be transported to the construction site and placed and finished in the forms.
Heat of Hydration of Cement || Hydration of Cement #2 ||
Stage 3 – Hydration Acceleration: The end of the dormant period shows the beginning of the setting at which time the cement starts to react more rapidly with water. This will result in the formation of new hydration products. Stage 4- Hydration Deceleration: This period will undergo formation of hydration products but the rate of reaction and the dissolution is very controlled and slow.
What chemicals are involved in hydration?
In chemistry, a hydration reaction is a chemical reaction in which a substance combines with water. In organic chemistry, water is added to an unsaturated substrate, which is usually an alkene or an alkyne. This type of reaction is employed industrially to produce ethanol, isopropanol, and butan-2-ol.
Which has more hydration energy nacl or KCL?
Which is more soluble in water $NaCl$ or $KCl$? Answer Verified Hint: We must have to know that the solubility is the ability of a compound, it may be a liquid, solid or gaseous substance to dissolve in solvent and there is a formation of a solution.
- Complete answer: Note:
Among these given compounds, sodium chloride is more soluble in water than potassium chloride. Because the solubility of a compound mainly depends upon the hydration energy and lattice energy. If the hydration energy of the compound is greater than lattice energy, the solubility is more.
Here, the lattice energy of potassium chloride is greater than its hydration energy. Therefore, potassium chloride is insoluble in water. But for sodium chloride, the hydration energy of sodium chloride is greater than its lattice energy. Hence, it is highly soluble in water. And the size of sodium ions is smaller than potassium ions.
Therefore, the sodium ion can easily create a hydration sphere around the ion than potassium ions. If the potassium chloride is dissolved in water, there is a formation of potassium and chloride ions. And when the sodium chloride is mixed with water, due to the covalent bonds, the salts will dissolve in water.We must know that the sodium chloride is more soluble than potassium chloride due to its small size and high hydration energy.
Which one of the following is highly hydrated?
Solution : ` Li^(o+)` due to highest positive charge density gets hydrated to maximum extent.
Which has maximum hydration energy Li+ Na+ K+ Rb+?
Correct option 1 Li+ > Na+ > K+ > Rb+ > Cs+ Explanation:Li⊕ having minimum radius so maximum hydration and maximum hydration radii.
Which ion liberates the most hydration energy?
varun 304 Points 5 years ago Hello, Be2+ is the right answer because see the below explanation below The hydration enthalpies of alkali metal ion decreases with increase in ionic sizes So, the order is Li+>Na+>K+>Rb+>Cs So hydration enthalpy for Li+ is more But Be2+ is also there right So ionic size for Li+>Be2+ so the size of Be2+ is less so hydration energy for Be2+ is more than Li+ AND WE HAVE ALSO OTHER METGOD TO SOLVE THIS PROBLEM ie small the size of ion the greater the hydration energy so BE2+ IS THE ANSWER please approve me if the answer is correct THANK YOU somi teez 105 Points 5 years ago hi, The extent of hydration of ion decreases with increase in ionic size, Li+>Na+>K+>Rb+>Cs and Be + is next to lithium, we know, atomic size decreases across a period so, the ionic size of Li+ > Be + hence, Be + has greatest hydration energy among all. if you go the answer approve it.
What is the heat of hydration of cement?
Hydration of Cement | Heat of Hydration |Stages of Hydration of Cement The hydration of cement is an exothermic reaction that is carried out when cement comes in contact with water. The reaction will result in several by-products that will contribute to the strength of the concrete or mortar formed. Please enable JavaScript
| Fig.1. Hydration Reaction – Changing Microstructure of Cement |
The chemical reaction that takes place between the cement and water is referred to as hydration of the cement. The hydration reaction is an exothermic reaction.The cement hydration will liberate a considerable amount of heat. This is called as Heat of liberation or Heat of Hydration.
The rate of development of heat is greatly influenced by the fineness of the cement. The normal cement generally produces 89-90J/g in 7 days and 100J/g in 28 days. The hydration process is not instantaneous. The reaction is faster in the early stages and will go decreasing with the time period.
| |
| Table.1: Bogues Compounds |
Hydration is an exothermic process, that will liberate heat through chemical reactions. The process of hydration can be easily followed by monitoring the production of heat that accompanies the reaction. This is done by civic mortar from a batch of concrete and weighing it into a bottle which is placed into an insulated container.
There are Five stages of cement hydration:
Initial Hydrolysis Advertisements Induction Period or the Dormant Period Acceleration Deceleration Steady State
| Fig.2.The Heat of Hydration – Calorimetry curve. |
/ol> Stage 1- Initial Hydrolysis: The initial dissolution of cement will result in the sort release of heat shown by the first peak in the calorimetry curve. Stage 2 – Induction or Dormant Period: After the initial dissolution process, the hydration products are precipitated on the surface of each cement particle.
Stage 3 – Hydration Acceleration: The end of the dormant period shows the beginning of the setting at which time the cement starts to react more rapidly with water. This will result in the formation of new hydration products. Stage 4- Hydration Deceleration: This period will undergo formation of hydration products but the rate of reaction and the dissolution is very controlled and slow.
