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Initial and Final Setting Time of Cement | Definition, Apparatus, Procedure, Observations.

“You only live once, but if you do it right, once is enough.”

During Construction using concrete, cement paste, mortar certain time is required for mixing, transportation, placing, compacting and finishing. During this time concrete, mortar, cement paste should be in plastic condition and should not harden and it is mandatory that one should use the concrete before it starts to loose its plasticity. So How should someone know how long is concrete workable? and How much travel time is permitted for concrete?

Well its Setting time that tells us how long concrete is going to be workable. Now the question is What is Setting Time of Cement?

Setting Time of Cement

The question was What is Setting Time?

Setting time of cement is the time required to stiffening of cement paste to a defined consistency. Setting time is then classified in two types Initial setting time and Final setting time based on plasticity.

What the is Initial Setting Time of Cement?

Time elapsed between water added and time at which cement paste just starts loosing its Plasticity is called as Initial Setting Time of Cement. Normally for OPC Initial Setting Time is 30 minutes but should not be more than 60 minutes.

Basically the time interval for which the cement products remain in the plastic condition is known as the initial setting time.

What is the Final Setting Time of Cement?

Time elapsed between water added and time at which cement paste completely loose its Plasticity is called as Final Setting Time. Normally for OPC Final Setting Time is 10 hrs and not more than that.

Basically it is time taken by the cement paste or concrete to harden sufficiently or completely loose its plasticity.

Significance of initial and final setting time of cement

Setting time of Cement plays a vital role in any kind of construction work. Concrete should not set too early nor too late. Concrete set before placing results in rigidity before placing or low workability. In the converse scenario, late setting will result in inadequate strength at desired age.

Initial setting time is time span between time of addition of water and the time when cement paste starts to loose its plasticity. That is why Initial setting time test is important for transportation, placing, compacting and curing of cement concrete.

Final Setting time is the time span between water added and the time when concrete completely loose its plasticity. Final setting time of cement helps in the safe removal of scaffolding.

Determination of Initial and Final Setting Time of Cement

Aim:

To determine Initial and Final setting time of Cement.

Apparatus:

1) Vicat Apparatus:

A device used to determine Standard Consistency and Setting Times consists of rod weighing 300 grams, having a needle at one end and supported in the frame with Graduated scale for measuring the Penetration. Also having a mould to put the cement.  

2) Needles for Tests :

  • Needle for Initial Setting Time: The needle is having a cross-sectional area of 1mm2. The end of the needle is flat.
  • Needle for Final Setting Time: The needle is circular having a cross-sectional area of 1mm2. The needle is fitted with a metal attachment. The end of the needle projects beyond the cutting edge.

3) Vicat Mould:

Vicat mould is having internal diameter 80 mm and 40 mm height. With non-porous base plate is provided at the base of the mould. Mould is having suitable clamping ring.  

4) Weight Balance:

To take the weight of Sample of Cement. It should at least be with least count of 1 gram.  

5) StopWatch:

It is a timer used to record the time. Stop watch should be used to note down the reading of Consistency Test.  

Procedure:

Preparation:

  1. First, take 300 grams of Cement in a pan and mix with the known percentage of water by weight of Cement, assume starting from 26% and then increase it by every 2% until the normal Consistency is achieved.
  2. With continuous mixing.
  3. Start the Stopwatch as soon as the water added to Cement.
  4. Now fill the paste into the Mould with a non-porous plate below.
  5. Level and Smoothen the surface of the paste.

Initial Setting Time Test:

  1. Place the mould in the Vicat Apparatus allow the Needle to touch the surface of paste and then quickly release allowing it to freely sink into paste.
  2. Repeat this procedure until the needle when released fails to penetrate the block beyond 5mm from the bottom of the mould.
  3. Record this time and this shall be the Initial setting Time.                                                                   

Final Setting Time Test:

  1. Replace the needle by final setting time needle.
  2. The cement shall be considered as finally set when, upon applying the needle gently on the surface of the test block, the needle makes an impression and fails to penetrate.
  3. The time elapsed between the time when water is added and the time at which the needle makes an impression on the surface of the test block shall be considered as Final Setting Time of Cement sample.

Figure:

Observations Table:

  • Weight of sample of Cement _ _ _ _ _gms
  • The Standard Consistency of given sample of cement is _ _ _ _ _%
  • Volume of Water added _ _ _ _ _ml
Sr. No.Setting TimePenetration (mm)
1
2
3
4

Calculations :

Formula for Initial Setting Time:

Initial Setting Time = T2 – T1

Formula for Final Setting Time:

Final Setting Time = T3 – T1

where,

T1= Time of addition of water to Cement

T2= Time when the needle released fails to penetrate the block beyond 5mm from the bottom of the mould.

T3= The time at which the needle makes an impression on the surface of the test block.

Results:

Initial Setting Time of given Cement is : __________

Final Setting Time of given Cement is : __________


Video Explanation on Initial and Final Setting Time of Cement:


Standard Setting Times for Different Type of Cement

Type of CementInitial Setting Time (Min)
Min
Final Setting Time (Min)
Max
OPC 3330600
OPC 4330600
OPC 5330600
Sulphate Resistant Cement30600
Super Sulphated Cement30600
Low Heat Cement60600

Setting Time of Concrete PPT

FAQs on Initial and Final Setting Time of Cement

What is the initial setting time of cement?

Time elapsed between water added and time at which cement paste just starts loosing its Plasticity is called as Initial Setting Time of Cement. Normally for OPC Initial Setting Time is 30 minutes but should not be more than 60 minutes.

What is the Final Setting Time of Cement?

Time elapsed between water added and time at which cement paste completely loose its Plasticity is called as Final Setting Time. Normally for OPC Final Setting Time is 10 hrs and not more than that.

How can we reduce the setting time of cement?

To reduce setting time gypsum is added during manufacture.
For further reduction of setting time one can always use Retarding Admixtures.

Why gypsum is added in cement?

Gypsum is added to reduce the setting time of cement by slowing down the rate of hydration of cement.


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