Procedure to Determine Setting Time of Cement –
Take 400 gm of cement for making a paste.The required quantity of water is 0.87 P, P = consistency of water. Water should be potable or distilled water. You can determine consistency from the standard consistency test of cement,Prepare a paste of weighed quantity of Cement and water.Maintain the time of gauging, gauging time is not less than 3 minutes and not more than 5 minutes. The gauging must be completed before any sign of setting occurs.Start a stop-watch at the instant when water is added to the cement. The gauging time is started to count from the time of adding water to the dry cement.The mould resting upon a non-porous plate, fill it with this pasteAfter completely filling the mould, smoothen the surface of the paste, making it level with the top of the mould. The mould may be slightly shaken for remove the air.
(a) Initial Setting Time of Cement
Place the mould under the rod bearing the needle. (needle for determining the initial setting time)Lower the needle slightly until it comes in contact with the surface of the test block and quickly release, allowing it to penetrate the test block.In the starting, the needle will completely penetrate the test block.Repeat this procedure until the needle fails to penetrate the block to the 5.0 ± 0.5 mm from the bottom of the mould.The period elapsing between the time when water is added to the cement and the time at which the needle fails to penetrate the test block to the 5.0 ± 0.5 mm from the bottom of the mould is called the initial setting time.
(b) Final Setting Time of Cement
To determine the final setting time the first needle is replaced by the (needle for determining the final setting time) needle with an annular attachment.When applying the needle gently to the surface of the mould, the needle makes an impression thereon.Cement called as final set while the attachment fails to make an impression on the surface of the test block.The period elapsing between the time when water is added to the cement and the time at which the needle fails to make an impression on the surface of the test block is called the final setting time.
- 0.1 What is the initial setting of cement?
- 0.2 Which apparatus used to determine the setting time of cement?
- 1 What is the initial setting?
- 2 What is the ASTM specification for the setting time of cement?
What is the initial setting of cement?
The initial setting of Portland cement is due to tricalcium aluminate. Tricalcium aluminate (C3A): This is also called Celite. It is the quickest one to react when the water is added to the cement.
What is the initial setting time of OPC cement?
Initial setting time should not be less than 30 minutes and final setting time should not be greater than 600 minutes as per IS 12269.
Which apparatus used to determine the setting time of cement?
Determination of Setting Time of Cement as per IS 4031 (Part 5) 1988 – Apparatus to determine Setting Time of Cement: Followings are the apparatus used in setting time test of cement paste : 01. Vicat Apparatus: The Vicat apparatus shall consist of
Vicat apparatus consists a frame has a movable rod with a platform at one end and the needle which can be attached at the other end. Needle:
I) Needle for determining the initial setting time – The needle shall have a diameter 1.13 ±05 mm, 50 ± 1 mm length and flat end. II) Needle for determining the final setting time – The needle shall be of the same diameter as a needle for initial setting time, but length shall be 30 ±1, and connected with a brass covering hollowed out.
Graduated Scale: length of graduated scale is 40 mm and the smallest division is 1 mm Vicat Mould: Mould is having an Internal diameter of 70 ± 5 mm at the top and 80 ± 5 mm at the bottom and a height of 40 ± 0.2 mm.
02. Weighing Machine: At a load of 1000 g, the allowable variation shall be ± 1.0 g.03. Stop Watch 04. Gauging Trowel 05. Measuring Cylinder 06. Tray Vicat Apparatusto Determine Setting Time of Cement
What is the initial setting?
2 The Setting Time – The setting time of cement includes the initial setting time and the final setting time. The initial time refers to the time that cement turns into paste by mixing with water and begins to lose its plasticity. And the time that cement completely loses its plasticity by mixing with water and begins to have a certain structural strength is known as the final setting time.
The national standards prescribe that the initial setting time of Portland cement should not be earlier than 45 min and the final setting time should not be later than 6.5 h. All the products off-grade at the initial setting time are spoiled products and those unqualified at the final setting time are sub-quality products.
The setting time of cement is measured by time determinator. The sample is the standard cement paste of which the temperature is 20 °C ± 3 °C and humidity is more than 90%. Various mineral components of the cement clinker are different in the water consumption of their normal consistency.
The finer the cement is ground, the more water the normal consistency will need. The normal consistency of Portland cement is within 24% ~ 30%. The setting time of cement is very important in the construction projects. The initial setting time should not be too fast in order to ensure that there is enough time to complete every process, such as casting, before the initial setting time; and the final setting time should not be too late in order to enable the cement to complete its setting and hardening as soon as possible after pouring and tamping to make the next process occur earlier.
Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845699550500049
What is the importance of determining setting time of cement?
Importance of Initial and Final Setting Time of Cement – Cement is a widely used material for making mortar and concrete for construction and building projects. After mixing cement with water, it takes time to place the cement paste in position. Initial setting time of cement possess a primary role in strength and it is mandated that cement paste is placed in position before it crosses initial setting time, that is approximately 30 minutes.
- Cement should set neither too rapidly nor too slowly. In the first case if a cement paste sets very rapidly there might be there might be insufficient time to transport and place the concrete before it becomes too rigid. In the second case too long a setting period tends to slow up the work unduly, also it might postpone the actual use of the structure because of inadequate strength at the desired age.
- Setting of cement should not be confused with hardening, which refers to the gain in mechanical strength after the certain degree of resistance to the penetration of a special attachment pressed into it.
- Determination of setting time is the time required for concretizing of cement paste to a defined consistency.
- During setting of cement, the initial chemical reaction of cement with water indirectly related to form aluminum-silicate compound.
- Initial setting time of cement paste is regarded as the time within which the cement can be molded in any desired shape without losing its strength.
- Initial setting time of cement is the time when the hardening of the cement starts and the cement paste starts losing its plasticity. We have the only time available for mixing the paste and placing it in position.
- Initial setting time test of cement is important for transportation, placing and compaction of cement paste.
- Determination of initial setting time duration is required to delay the process of hydration or hardening.
- Final setting time of cement is regarded as the maximum time when the cement paste completely loses its plasticity and becomes hard.
- This is the time taken for the cement paste to reach its optimum strength to reach the highest tensile strength possible by the cement paste and attain the shape of the mould in which it is cast.
- Determination of final setting time facilitates safe removal of scaffolding or form.
- During the final setting time, primary chemical reaction of cement with water is almost completed.
- Determination of initial and final setting time of cement is important because different types of cement have different hydration and hardening time.
Which cement sets faster OPC or PPC?
OPC cement hardens faster than PPC, has higher heat of hydration and thus it requires more care in curing.
What is the ASTM specification for the setting time of cement?
An ASTM C403 initial time or setting of 3 to 5 hours for a concrete mixture in the laboratory is considered reasonable. It is important for the time of setting to be consistent from load to load.
What is the initial setting?
Test Procedure : –
A cement paste is prepared by adding water 0.85P% by weight of cement. The time of mixing should not be less than 3 minutes and should not be more than 5 minutes. Now the paste is filled in the Vicat mould and the top is levelled off. The mould is now placed under the square needle with annular collar and is brought down touch the surface of the paste. Now the square needle with annular collar is suddenly released and allowed to make on impression on the cement paste by its own weight. The impression made by this square needle with annular collar is observed. The whole experiment is repeated with incremental time intervals until such a time when the square needle makes an impression on the paste while the annular collar fails to do so. The time elapsed between the moments when water is added to the cement to the time when the square needle makes an impression on the paste while the annular collar fails to do so is known as the Final Setting Time of the cement. The final setting time of cement should not be more than 600 minutes for Ordinary Portland Cement.
Also Read : Workability of Concrete & Factors Affecting It
Is 4031 initial setting time?
Initial setting time is that time period between the time water is added to cement and time at which 1 mm square section needle fails to penetrate the cement paste, placed in the Vicat’s mould 5 mm to 7 mm from the bottom of the mould. Final setting time is that time period between the time water is added to cement and the time at which 1 mm needle makes an impression on the paste in the mould but 5 mm attachment does not make any impression.