Free 10 Questions 30 Marks 10 Mins The setting and hardening of cement after addition of water is due to hydration of some of the constituent compounds of cement such as Tricalcium aluminate, Tricalcium silicate, Dicalcium silicate, and Tetra calcium aluminoferrite.
These compounds are known as Bogue’s Compounds. Hydration of Bogues Compounds Tricalcium aluminate (C 3 A): Celite is the quickest one to react when the water is added to the cement. It is responsible for the flash setting. The increase of this content will help in the manufacture of Quick Setting Cement.
The heat of hydration is 865 J/Cal, Tricalcium silicate (C 3 S): This is also called as Alite, This is also responsible for the early strength of the concrete. The cement that has more C 3 S content is good for cold weather concreting. The heat of hydration is 500 J/Cal,
- Dicalcium Silicate (C 2 S): This compound will undergo reaction slowly.
- It is responsible for the progressive strength of concrete.
- This is also called as Belite,
- The heat of hydration is 260 J/Cal.
- Tetra calcium Alumino ferrite (C 4 AF): This is called as Felite,
- The heat of hydration is 420 J/Cal,
- It has the poorest cementing value but it responsible for long term gain of strength of the cement.
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- 1 What is responsible for hardening cement?
- 2 Which is responsible for initial setting of cement?
- 3 Which compound is responsible for setting of cement?
- 4 Which of the following helps in setting the cement?
What is responsible for hardening cement?
The setting of cement and hardening of concrete – planete-tp : All about public works Cement hardens when it comes into contact with water. This hardening is a process of crystallization. Crystals form (after a certain length of time which is known as the initial set time) and interlock with each other.
Concrete is completely fluid before the cement sets, then progressively hardens. The cement and water mixture that has crystallized in this way encloses the aggregate particles and produces a dense material. The concrete continues to harden over several months. Hardening is not a drying process and can very well take place in water.
Heat speeds up the setting and hardening of cement, and cold slows it down and can even completely stop the processes. In order to crystallize or hydrate) cement requires a quantity of water equal to 25% of its weight. But in order for it to be laid and remain sufficiently workable, twice this amount is usually required. However, too much water can reduce the strength and durability of the concrete.
Which is responsible for initial setting of cement?
Tricalcium Aluminate (C3A) – It is responsible for the initial setting time, high heat of hydration and has greater tendency to volume changing causing cracking.
Which compound is responsible for setting of cement?
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.
Which of the following is responsible for the hardening of hydraulic cement?
Portland cement – Portland cement, a form of hydraulic cement, is by far the most common type of cement in general use around the world. This cement is made by heating limestone (calcium carbonate) with other materials (such as clay ) to 1,450 °C (2,640 °F) in a kiln, in a process known as calcination that liberates a molecule of carbon dioxide from the calcium carbonate to form calcium oxide, or quicklime, which then chemically combines with the other materials in the mix to form calcium silicates and other cementitious compounds.
- The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum ( CaSO 4 ·2H 2 O ) into a powder to make ordinary Portland cement, the most commonly used type of cement (often referred to as OPC).
- Portland cement is a basic ingredient of concrete, mortar, and most non-specialty grout,
The most common use for Portland cement is to make concrete. Portland cement may be grey or white,
What is setting and hardening of cement with equation?
6H2O + Ca(OH)2 +250 KJ/Kg Dicalcium silicate tobermonite gel Page 3 3 Final setting and hardening of cement paste is due to the formation of tobermonite gel and crystallisation of calcium hydroxide and hydrated tricalcium aluminate.2(2 CaO.SiO2) + 6 H2O.3 CaO.2SiO2.3H2O + 3Ca(OH)2 +500 KJ/Kg.
What is responsible for rapid hardening cement high early strength?
It has a higher proportion of limestone and shale (Clinker), which results in early high strength. It has a high proportion of tricalcium silicate (C3S) which boosts up the strength gain, in early stages due to higher heat of hydration. Shrinkage during curing and hardening of cement is less in case of RHC.
Which of the following helps in setting the cement?
Consider the following statements: 1. Setting and hardening of cement takes place after the addition of water.2. Water causes hydration and hydrolysis of the constituent compounds of cement which act as binders. Which of these statements is/are correct? No worries! We‘ve got your back. Suggest Corrections 0 : Consider the following statements: 1. Setting and hardening of cement takes place after the addition of water.2. Water causes hydration and hydrolysis of the constituent compounds of cement which act as binders. Which of these statements is/are correct?
What is the role of gypsum in setting of cement?
(2) The Mixing Amount of Gypsum – Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat.
The major reason is that C 3 A in the clinker can dissolve in water quickly to generate a kind of calcium aluminate hydrate, a coagulant agent, which will destroy the normal use of cement, the retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C 3 A quickly to generate calcium sulfoaluminate hydrate (ettringite) which deposits and forms a protection film on the cement particles to hinder the hydration of C 3 A and delay the setting time of cement.
If the content of gypsum is too little, the retardation affect will be unobvious. Too much gypsum will accelerate the setting of cement because gypsum can generate a coagulating agent itself. The appropriate amount of gypsum depends on the content of C 3 A in the cement and that of SO 3 in gypsum, and it also related to the fineness of cement and the content of SO 3 in clinker.
The amount of gypsum should account for 3% ~ 5% of the cement’s mass. If the content of gypsum exceeds the limit, it will lower the strength of cement and it can even lead to poor dimensional stability, which will cause the expanded destruction of cement paste. Thus, the national standard requires that the content of SO 3 should not be more than 3.5%.
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