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. |
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
Civil Engineering – Concrete Technology – Discussion
Contents
- 0.1 Which of the following cement compound liberates lot of heat during early stage?
- 0.2 Which of the following cement type is used in high temperature applications?
- 1 What is high heat cement?
- 2 Does cement generate heat?
- 3 Which element has highest heat hydration?
- 4 Which compound will absorb the maximum amount of heat?
- 5 What is the role of C3A and C4AF in the setting time of cement?
- 6 What is C3S and C2S?
- 7 Which among the following admixtures are used in hot climate?
- 8 Which constituent of cement affects the early setting?
Which of the following cement compound liberates lot of heat during early stage?
The correct option is (b) C3S To elaborate: C3S having a faster rate of reaction accompanied by greater heat generation developes early strength of the paste.
Which Bogues compound has maximum heat of hydration?
Tricalcium Aluminate (C3A) is the bogue’s compound maximum heat of hydration.
Which compound is liberates higher heat a C2S B C3S C C3A D c4af?
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. |
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
table>
Civil Engineering – Concrete Technology – Discussion
Which of the following cement type is used in high temperature applications?
Which of the following cement is used in high temperature applications?A.Expansive cement B.High alumina cement C.Portland blast cement D.Portland pozzolan cement Answer Verified Hint: High alumina cement form ceramic bonds at elevated temperature. Expansive cement is used for preventing water leakage and Portland cement is used widely on a daily basis for various purposes.
Complete step by step answer: Thus, the correct option is B. Note:
Cement is a light grey and fine powdered. It is a homogeneous mixture of silicates and aluminates of calcium. Ninety percent of cement is formed of aluminates and silicates. Raw material required to make cement is limestone, clay and gypsum. Limestone provides calcium hydroxide, clay contributes aluminium oxide and silica and gypsum contribute hydrated calcium sulphate.
- Gypsum is also used to slow down the process of setting of cement in order to increase hardness of cement.
- When water is mixed to cement and the mixture is left it becomes very hard, this is known as the setting of cement.
- Portland cement is widely used cement all across the world.
- It is a mixture of mortar, concrete, stucco and grout.
The fine powdered Portland cement is made from heating limestone and clay, with around three percent of gypsum. Its production contributes about 10 percent of present carbon dioxide emissions in the world today. Five types of Portland cement are present namely: general Portland cement, Portland composite cement, Portland blast furnace cement, Portland pozzolanic cement and composite cement.
In the given question, Portland blast furnace cement is the one which has a high contribution of blast furnace slag in it. Portland pozzolanic cement is the one which has about 55 percent contribution by pozzolanic particles.High alumina cement is produced by fusing alumina (bauxite) and lime. This cement is resistant to chemical attacks and chemical corrosion and also hardens at a very high rate.
High alumina cement is used for high temperature applications as alumina provides high tensile and mechanical strength to the cement even at high temperature. It acts as bonding material when added in refractory castables because it forms ceramic bonds at high temperature.
Thus high alumina cements can be used even at high temperature. On the other hand, expansive cement is the one which is used to minimize cracking in concrete as it helps by preventing water leakage from the concrete. Expansive cement as they generate volume expansion and do not shrink and improve ordinary cement concrete.Mortar is a mixture of cement, sand and water to give a proper consistency.
Concrete is a mixture of cement, sand gravel and water. And when concrete is filled in beams of iron bars, it is known as RCC or reinforced concrete cement. : Which of the following cement is used in high temperature applications?A.Expansive cement B.High alumina cement C.Portland blast cement D.Portland pozzolan cement
What is high heat cement?
: a cement capable of resisting high temperatures without fusing, softening, or spalling and suitable for the bonding of refractory materials
Does cement generate heat?
The heat produced by concrete during concrete curing is called heat of hydration. This exothermic reaction occurs when water and cement react. The amount of heat produced during the reaction is mostly related to the composition and fineness of the cement.
Which compound has the highest heat of hydrogenation?
As the conjugation increases, the heat of hydrogenation decreases. Thus, alkene (C) with 2 isolated double bonds has the highest heat of hydrogenation.
Which element has highest heat hydration?
Be2+ ion has small size and high charge. Hence, it has high polarizing power and can attract several water molecules. Thus it has highest hydration energy among the given ions.
Which compound will absorb the maximum amount of heat?
Expert-Verified Answer NH4NO3 (delta H = + 16.85 ) will absorb the maximum amount of heat when dissolved in the same amount of water.
What is C3A and C3S in cement?
Master of Science at University of Trondheim (NTH), Norway – Published Nov 25, 2015 C3S is the main contributor to Strength of cured Concrete in early phases. C3S & C3A are the main contributors to Heat in the early phases. C3A develops approximately 840 Joules/ gram and C3S 500 Joules / gram.
- Cement used in Concrete contains approximately 5 times as much C3S as C3A.
- Thus C3S is the main contributor to the Heat Development as well.
- To Predict Temperature & Strength Development, C3S & C3A content must be stable! But known Regulations does not specify limits! It turns out that C3S content may vary as much as 22% between suppliers and even between batches from the same supplier.
C3A content may vary as much as 16%! (1) HPC-09 v6 has means of Discrepancy Detection that reveals these Concrete Mix variations and provides Safe Maturity Calculations ! HPC-09 v6 combined with the Quality Control Regime of the plant provides the best Quality Control of your end product.
- Variation in Cement Properties and Its Effect on Quality of Concrete, Thushara PRIYADARSHANA and Ranjith DISSANAYAKE, University of Peradeniya, 20400, Sri Lanka
- “Integrated Materials and Construction Practices for Concrete Pavement”. A State-of-the-Practice Manual, FHWA Publication No. HIF-07-004, December 2006
- “Predicting Temperature Rise and Thermal Cracking in Concrete”. Michael Edward Robbins 2007
-
What is the role of C3A and C4AF in the setting time of cement?
Chemistry of Hydration – It is assumed that each compound hydrates independently of others in Portland cement. This is not completely true because interaction between hydrating compounds will affect the mix. Calcium Silicates – The hydration reaction of the two calcium silicates, which make up the largest percent of Portland cement, are similar.
- The principle products are: 1) calcium silicate hydrate, poorly crystalline material of extremely small particle size and 2) calcium hydroxide, a crystalline material. The reaction can be measured by the rate of heat generation.
- Stage 1 – Rapid heat generation (15 min.) – on mixing with water, calcium and hydroxide ions are released from the surface of the C 3 S; pH rises to a very alkaline solution. When the calcium and hydroxide reach critical concentrations, crystallization of CH and C-S-H begins. Early chemical reactions are temperature dependent.
- Stage 2 – Dormant period – causes cement to remain plastic (2-4 hours). The reaction slows. CH crystallizes from the solution, C-S-H develops on the surface of the C 3 S and forms a coating. As the thickness increases, the time it takes water to penetrate the coating increases, thus the rate of reaction becomes diffusion controlled. C 2 S hydrates at a slower rate because it is a less reactive compound.
- Stage 3 – Acceleration period – Critical concentration of ions is reached and silicate hydrates rapidly, maximum rate occurs at this stage. Final set has passed and early hardening begins (4-8 hours).
- Stage 4 – Deceleration – rate of reaction slows; completely diffusion dependent reaction.
- Stage 5 – Steady state – constant rate of reaction (12-24 hours). Temperature has little effect on hydration at this point.
Tricalcium Aluminate – Hydration of C 3 A occurs with sulfate ions supplied by dissolved gypsum. The result of the reaction is calcium sulfoaluminate hydrate, called “ettringite” after a naturally occurring mineral.
- If the supply of sulfate from the gypsum is exhausted before the C 3 A is completely hydrated, a second reaction can occur. The product of this reaction is monosulfoaluminate. This reaction may occur before the formation of the ettringite if the reaction of C 3 A and the sulfate ions is faster than the gypsum will allow.
- The ettringite decreases the reaction by forming a diffusion coating around the C 3 A similar to the reaction of C 3 S. The coating can be broken down by the conversion to monosulfoaluminate.
- If the monosulfoaluminate is exposed to another source of sulfate ions, the a new reaction will occur forming more ettringite. This new formation causes volume to increase and leads to tensile cracking. This tendency is the basis for sulfate attack of Portland cements.
- In the absence of sulfates, C 3 A reacts with water to form two unstable calcium hydrates which later convert to hydrogarnet. This is the same process found in HAC. A pure C 3 A paste will not develop significant strength.
Ferrite Phase (C 4 AF) forms the same hydration products as C 3 A, with or without gypsum. The reaction is slow and is decreased further by gypsum. If the iron oxide content is increased, the reaction is slower.
- Experience has shown cements low in C 3 A and high in C 4 AF are sulfate resistant. The conversion from ettringite to monosulfoaluminate is inhabited by the presence of the iron component.
- ** The rate of hydration is on the order of C 3 A > C 3 S > C 4 AF > C 2 S. Reactions for even identical compounds may vary due to: 1) fineness, 2) rate of cooling of clinker, and 3) impurities.
Some general comments on the properties of hydration products affecting the overall behavior of the cement. C-S-H, calcium silicate hydrate – very poor crystallinity; the exact chemical compound is variable. The ratio of C/S varies between 1.5 and 2.0 and depends on many factors; temperature, w/c ratio, impurities, etc.
Likewise, measures of the water content vary considerably. Because of the poor crystallinity, C-S-H develops very small irregular particles and consequently a very high surface area. In general, the surface area of the hydrated cement is about 1000 times larger than the unhdyrated cement. Therefore, the increase in surface area greatly influences physical properties of the C-S-H hydrate.
Considerable work has been done in modeling the structural components of C-S-H, with much disagreement among scientists. C-S-H is considered a layer structure composed of calcium silicate sheets randomly connected by strong ionic-covalent bonds. The remainder of the interlayer space is classified as: 1) capillary pores, relatively large openings where water can form menisci; 2) micropore, smaller spaces where water cannot form menisci.
- Powers-Brunauer – a chemical structure model based on the layered claylike configuration. The sheets are randomly arranged and contain absorbed water on their surfaces. Water can penetrate the interlayer, micropore region. Interlayer water can be permanently removed with strong drying.
- Feldman and Sereda – a model composed of a completely random array of single layers forming irregular interlayer space. Water can move in and out of the interlayer space even after drying.
- Munich – a physical model where C-S-H is considered a three-dimensional arrangement of colloidal particles. The chemical nature of the model is secondary. Van der Walls’ forces bind surfaces together, but strong covalent bonds are more common. Water is attracted to the solid particles resulting in disjoining pressures which reduce particle interaction.
*** In all these models, water affects the structure of the C-S-H. As water is removed from capillaries, a resultant compressive stress is induced. Loss of interlayer water affects particle or sheet bonding. Calcium Hydroxide – a well understood hexagonal crystalline material.
Crystals are much larger than C-S-H particles and are sometimes visible to the naked eye. Calcium Sulfoaluminate (ettringite) – These hexagonally-shaped prism crystals are considerably longer than CH crystals. Large clusters of ettringite needles may be visible in concrete affected by sulfate attack. Monosulfoaluminate tends to form very thin, hexagonal plates.
The development of cement microstructure relates to the five chemical stages described earlier in this chapter. C-S-H – the largest component of the cement paste (50-70%) and is the most important component in the hydration process. The amount of C-S-H coating on a C 3 S grain is very small during stage 2 of hydration and increases rapidly in stage 3.
- The spines of the forming C-S-H radiate outward from each grain with the bulk of the material below the spines.
- As the C-S-H hydrates further, the coating thickness grows forcing the outward spines of adjacent particles to interlock to form solid bonds.
- As hydration continues the intermeshed spines contribute to an increase in the undercoating of C-S-H growth.
The effect is to bond the cement grains together with the C-S-H coating. CH – constitutes 20-25% of the cement volume. In the acceleration stage, CH grows in the capillary pore space. CH will only grow in free space; on encountering another CH crystal it will grow in another direction; also it will grow completely around a hydrating cement grain.
- The latter effect gives the CH a larger apparent volume in cement pastes than it would have as a pure crystal.
- Calcium Sulfoaluminate – a small component of cement pastes (10-15%) having little effect on microstructure.
- Young spiny ettringite crystals grow into capillary space and later convert to flat monosulfoaluminate crystals.
There will be unhydrated residues in the cement paste, mainly caused by calcium hydroxide, even in very matured hydrated pastes. Porosity – a major component of microstructure which will influence paste properties. Pore size distribution is difficult to measure.
- Capillary pore – space formed between hydrating gains.
- Gel pores – very small spaces in the C-S-H coating. Constitutes the bulk of porosity in a cement paste.
Hydration products have lower specific gravities and larger specific volumes than their parent cement compounds. Therefore, every hydration reaction is accompanied by an increase in solid volume.
- Calcium Silicates – hydration of these materials is not accompanied by an increase in volume. Recall, these crystals will only occupy free space. If this space is filled, the growth or hydration will stop.
- Calcium Aluminate – The hydration product of this material (ettringite) will continue to form even when a solid surface is encountered. Since there is no volume in which the crystal can grow, internal pressures develop.
Volume change is directly related to porosity. It is possible to calculate pore space by measuring the loss of evaporable water and nonevaporable water. The evaporable water describes water held in capillary and gel pores. This amount can be determined by oven drying a sample.
- Nonevaporable water is a measure involving the microstructure of the hydration product and is obtained from a paste heated to very high temperatures (1000 C0).T.C.
- Powers developed several empirical relationships for degree of hydration based on the amount the two types of water described above.
- W n = 0.24a g/g of original cement where a = degree of hydration and w n = nonevaporable water w g = 0.18a g/g of original cement where w g = gel water or evaporable water Other relationships for volume of hydration products and porosity are available (see p.105).
Based on these, a minimum water/cement ratio relationship for complete hydration can be formed. w min = ( w n + w g ) g/g of original cement ( w/c ) min = 0.42a Therefore, for complete hydration, the w/c ratio should not fall below 0.42. However, complete hydration is not required for high ultimate strength.
This means that paste with low w/c ratios will self-desiccate unless external water is added. Generally, this is not a problem in the field. This website was originally developed by Charles Camp for his CIVL 1101 class. This site is maintained by the Department of Civil Engineering at the University of Memphis,
Your comments and questions are more than welcome.
What is C3S and C2S?
For that, a series of experiments were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement) and their mixtures, in order to obtain different C-S-H gel structures during their hydration.
Which of the following material are used for high temperature application?
Materials Science Questions and Answers – High Temperature Alloys This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “High Temperature Alloys”.1. Which of the following is not an alloy? a) Duralumin b) Bismuth c) Magnalium d) Alnico View Answer Answer: b Explanation: Bismuth is a metal with symbol Bi and atomic number 83.
- Duralimn is an alloy of copper, magnalium is an alloy of magnesium and Alnico is an alloy of aluminium, copper and cobalt.2.
- Which of the following is a high temperature alloy resistant to? a) Tensile compression b) Tensile elongation c) Creep d) Fatigue View Answer Answer: c Explanation: Alloys resistant to creep have high melting temperature and therefore are high temperature alloys.3.
Alloys resistant to creep have a high modulus of elasticity. a) True b) False View Answer Answer: a Explanation: The above statement is true. An alloy which is resistant to creep have a high modulus of elasticity and have high melting point thus giving then the name high temperature alloys.4.
Which of the relationship holds? a) Higher the melting temperature greater is the elastic modulus b) Lower the melting temperature greater is the elastic modulus c) Higher the melting temperature smaller is the elastic modulus d) There is no relationship between the melting temperature and elastic modulus View Answer Answer: a Explanation: The melting temperature of an alloy and its modulus of elasticity hold a direct relationship.
Therefore, higher the melting temperature greater is the elastic modulus.5. Which of the following doesn’t have high resistance to creep? a) Stainless steel b) Refractory metals c) Superalloys d) Magnesium View Answer Answer: d Explanation: Stainless steel, refractory metals and super alloys have resistance to creep and hence are used for high temperature usage.
Magnesium doesn’t have a high resistance to creep.6. Which of the following does not enhance the creep resistance of an alloy? a) Solid-solution alloying b) Addition of a dispersed phase c) directional solidification d) Heat treatment View Answer Answer: d Explanation: Heat treatment does not enhance the creep resistance of an alloy.
Solid-solution alloying and addition of dispersed phase are used for that outcome. Other advanced techniques like directional solidification can also be employed.7. Which of the following is created by directional solidification? a) Single crystal components b) Polycrystalline components c) Short grains d) Elongated grains View Answer Answer: a Explanation: In directional solidification, highly elongated grains or single-crystal components are formed.8.
Controlled unidirectional solidification of an alloy is a technique to increase creep resistance. a) True b) False View Answer Answer: a Explanation: The above statement is true. Controlled unidirectional solidification of alloys is a technique used to increase the creep resistance of an alloy. Sanfoundry Global Education & Learning Series – Materials Science.
To practice all areas of Materials Science,, Next Steps:
Get Free Participate in Become a Take Chapterwise Practice Tests: Chapterwise Mock Tests:
, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry, He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at, Subscribe to his free Masterclasses at & technical discussions at, : Materials Science Questions and Answers – High Temperature Alloys
Which among the following admixtures are used in hot climate?
Which of the following admixtures are used in the constructi Free 10 Questions 10 Marks 10 Mins Explanation: Retarders are chemicals that delay the initial setting time of concrete, Their chemical is often used in hot weather to counter the rapid setting due to high temperature. Therefore, retarders often used in the construction of oil well at which temperature increases up to 200°.
Admixtures Functions Typical compounds Application Disadvantages Accelerating admixtures or accelerators More rapid gain of strength or higher early strength. More rapid setting. - Calcium chloride Calcium formate Triethanolamine (TEA)
- Soluble inorganic salts
- Sodium nitrite
- Sodium sulphate
- Sodium aluminate
- Sodium silicate
1. Normal rate of strength development at low temperature.2. To counter retarding effects 3. Shorter stripping times.4. Plugging of pressure leaks.5. Sprayed concreting. 1. Possible cracking due to heat evolution.2. Possibility of corrosion of embedded effects reinforcement. Retarding admixtures or retarders Delayed setting - Soluble carbohydrate
- derivatives:
- starch
- Hydroxylated carboxylic acids,
- Inorganic retarders
- Sugars
1. Maintain workability at high temperatures.2. Reduce rate of heat evolution.3. Extend placing times, e.g., ready-mixed concrete.4. Prevent cold joint formation. May promote bleeding. Water-reducing accelerators Increased workability with faster gain of strength. Mixtures of calcium chloride and lignosulfonate. Water reducer with faster strength development. Risk of corrosion. Water-reducing retarders Increased workability and delayed setting Mixtures of sugars or hydroxylated carboxylic acids and lignosulfonate. Water reducer, with slower loss of workability. Air-entraining agents Entrainment of air into concrete. Natural wood resins, fats, lignosulfonates, alkyl sulfates, sodium salts of petroleum, sulfonic acids. Enhanced durability to frost without increasing cement content, improvement in workability, lowered permeability and cellular concrete. Careful control of air content, water-cement ratio, temperature, type and grading of aggregate and mixing time is necessary. Damp-proofing or water-proofing agents 1. Water-repellent, i.e. prevention of water from entering cap 2. Reduced water permeability of concrete. Potash soaps, calcium-stearate, aluminium-stearate, butylstearate, petroleum 1. Reduced permeability.2. Enhanced durability.3. Increased freeze-thaw resistance.4. Reduced drying shrinkage.5. Reduced surface staining.6. Water tightness of structures without using every low water-cement ratio. 1. Not efficient under high hydrostatic pressure.2. Requires low water-cement ratio and full compaction. Plasticizers (water reducers)-8 to 15 percent water reduction Higher flowability Hydroxylated carboxylic acid derivatives Calcium and sodium lignosulfonates. 1. Higher workability with strength unchanged.2. Higher strength with workability unchanged.3. Less cement for same strength and workability. Certain special types of cements like sulphate resistant cement (low C 3 A content) and expansive cement do not perform well. Superplasticizers (Super-water reducers) – 15 to 30 per cent water reduction Greatly enhanced workability. Sulfonated Melamine formaldehyde resin, sulfonated naphthalene-formaldehyde resin, Mixtures of saccharates and acid amides. 1. Water reducer, but over a wider range.2. Facilitate production of flowing or self-leveling concrete 1. Tendency to segregate.2. Flowability is not long lasting.3. During hot weather the workability retention period decreases fast. India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses Practice Question Bank Mock Tests & Quizzes Trusted by 3.4 Crore+ Students : Which of the following admixtures are used in the constructi
Which of the following compound is responsible for early setting of cement?
Ruchir said: (Jun 12, 2018) Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength. In general, the early strength of Portland cement concrete is higher with increased percentages of C3S. Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days. Which compound is responsible for early heat of hydration?
C3S readily reacts with water, producing more heat of hydration and is responsible for early strength of concrete.
Which component of cement provides early strength?
1. Introduction – The compressive strength achieved in concrete is one of the most important and desirable properties of concrete. Many admixtures have been tried by experts to achieve the desired compressive strength. This paper aims at achieving compressive strength in concrete; however, the authors of the paper have tried to use a nutrition medium containing a bacterium named Sporosarcina pasteurii as an admixture in concrete.
- The focus of the work has been to decrease the time taken by the cement to hydrate and achieve maximum strength at early ages.
- Early strength gain in normal concrete is mainly associated to the water/cement ratio.
- Mixes with low water cement ratio gain strength more rapidly than those with higher water cement ratio.
This is because the cement grains are closer to one another and a continuous system of gel is established more rapidly. There are actually many different types of accelerators present in the market but the common problems posed by the accelerators are low slump, low initial setting time, and thus reduced workability.
- These adverse properties of accelerators refrain most of the experts from using the same in concrete.
- The use of blended cements presently has also been on rise in construction industry; blended cements with a defined amount of cement replaced with flyash are commonly being used.
- The addition of flyash to cement, however, has little disadvantage; that is, for flyash to hydrolyse and form into a strong component like cement it needs Ca(OH) 2,
The Ca(OH) 2 is a biproduct of cement hydration process; hence for the flyash to form the C-S-H gel it requires calcium hydroxide in adequate quantity and this can occur only if adequate cement hydrolisation takes place. If calcium carbonate is present in cement, the hydrolisation process takes place quickly and inturn provides Ca(OH) 2 in requisite quantity for flyash to hydrolyse and give the desired compressive strength.
- Sporosarcina pasteurii formerly known as Bacillus pasteurii is a bacterium with the ability to precipitate calcium carbonate in the presence of any carbonate source.
- This microorganism is well known for its resistive properties to resist the harsh conditions of sea water and very high temperatures whichare generally found in shallow waters and in Sahara desert.
This bacterium is used in the present work for checking the improvement in the compressive strength of concrete. Sporosarcina pasteurii secretes calcium carbonate. This calcium carbonate inturn acts as a positive catalyst for the cement hydration process as discussed by Ramachandran, Péra et el.
, and Kakali et al. It was found that the Sporosarcina pasteurii bacteria attain their maximum activity rate at 16 hours and maintain this till the time the nutrition medium is consumed. Thus the secretion of maximum amount of calcium carbonate takes place only 16 hours after the concrete has been mixed, thus providing enough workable time for concrete.
Also it has been seen that this nutritional medium neither allows for the loss in slump nor causes immediate setting of the concrete. In the present work the bacterial admixture has been added in different compositions and concentrations along with other products like urea, sodium carbonate, calcium chloride, and so forth in differing proportions to study its impact on compressive strength at 3, 7, 14, and 28 days of curing.
- The compressive strength obtained of bioconcrete that is with Sporosarcina pasteurii bacteria is compared with the strength gained by controlled concrete at 3, 7, 14, and 28 days, respectively.
- The work also tries to examine the use of sodium carbonate along with the nutrient medium in concrete and simulate the chemical reaction which is the major contribution of the authors to the research wherein earlier only urea had been tried by experts.
The below chemical reactions ( 1 ) and ( 2 ) depict the formation of calcium carbonate that acts like a catalyst for the formation of C-S-H gel which is required for the hydrolization of cement. Using urea, (Kashyap and Radhakrishna ). Using sodium carbonate, (experimental work).
Which constituent of cement affects the early setting?
Free Gujarat Engineering Service 2019 Official Paper (Civil Part 1) 150 Questions 150 Marks 90 Mins Explanation: The initial setting of Portland cement is due to tricalcium aluminate. Tricalcium aluminate (C 3 A):
This is also called Celite. It is the quickest one to react when the water is added to the cement. It is responsible for the flash setting.
Tricalcium silicate (C 3 S):
This is also called Alite, Tricalcium silicate hydrates quickly and contributes more to the early strength
Tricalcium silicate (C 2 S):
This is also called as Belite, The contribution of dicalcium silicate takes place a fter 7 days and may continue for up to 1 year.
Tetra calcium Alumino ferrite (C 4 AF):
This is called as Felite, Tetracalcium alumino-ferrite is comparatively inactive.
The rate of hydration is highest for C 4 AF and heat of hydration is highest for C 3 A. From the above, the decreasing order of rate of hydration of Portland cement compounds is C 4 AF > C 3 A > C 3 S > C 2 S. For the heat of hydration, decreasing order of heat of hydration of portland cement is C 3 A > C 3 S > C 4 AF > C 2 S Latest GPSC Engineering Services Updates Last updated on Oct 1, 2022 The Gujarat Public Service Commission (GPSC) has released a new notification for the GPSC Engineering Services Recruitment 2022. The commission has released 28 vacancies for the recruitment process. Candidates can apply for the applications from 15th October 2022 to 1st November 2022 and their selection will be based on Prelims, Mains and Interview. Candidates with a Graduation degree as the basic GPSC Engineering Services Eligibility Criteria are eligible to appear for the recruitment process. The finally selected candidates will get a salary range between Rs.53100 to Rs.208700.
