Initial and final setting time of cement test done to find out the time when the cement starts losing its plasticity and the time when the cement has completely lost its plasticity
Initial setting time of cement is the time in-between the addition of water in cement and when the cement starts losing its plasticity. Cement can be moulded into any desired shape without losing its strength during this period.
The final setting of time is the time from the addition of water in cement to when the cement has completely lost its plasticity. During this period, the cement paste becomes a hard mass and reach its optimum strength.
Initial and final setting time of cement test can be determined with a simple experiment using the Vicat apparatus.
Apparatus required
- Vicat apparatus
- Weighing machine
- Trowel
- Stopwatch
- Measuring Cylinder
Procedure
1) For the initial setting time of cement (OPC cement say)
- Let us take 300 gm of cement-free from lumps to measure the initial setting time of cement.
- Then, 0.85P of water is added to the cement.
i.e. =76.5 ml
where, P= Normal consistency of cement= 30% for 0PC cement
- Now, 76.5 ml of water is added to 300 gm of cement and mixed well. The time is recorded.
- The mixture is placed and levelled well in Vicat mould within 3-5 minutes of adding water to the cement and placed under Vicat apparatus.
- 1 mm² needle is used to find the initial setting time of cement.
- At first, the needle is kept in such a way that it just touches the surface of the mould and then it is allowed to fall freely.
- The test is repeated within 2 minutes till the needle penetrates 5- 7 mm from the bottom of the mould. The time is recorded.
- Initial setting time is calculated using the formula:
Final Setting Time = T3 – T1
Where T1=Initial time = time when the mixture is placed within the mould.
T2= Final time = time when the needle penetrates 5-7 mm from the bottom of the mould.
- The initial setting time of OPC cement is 30 minutes.
2) For the final setting time of cement
- Let us take 300 gm of cement-free from lumps to measure the final setting time of cement the same as in the initial setting time experiment.
- Then, 0.85P of water is added to the cement.
where, P= Normal consistency of cement= 30% for 0PC cement
- Now, 76.5 ml of water is added to 300 gm of cement and mixed well. The time is recorded.
- The mixture is placed and levelled well in Vicat mould within 3-5 minutes of adding water to the cement and placed under Vicat apparatus.
- 5 mm² annual collar is used to find the final setting time of cement.
- The collar is set in the apparatus and allowed to fall freely.
- The test is repeated within 30 minutes.
- Final setting time of cement is the time when the collar doesn’t make an impression on the mould on falling. The time is recorded.
- Final setting time is calculated using the formula:
Final Setting Time = T3 – T1
Where T1=Initial time=time when the mixture is placed in the mould.
T3=Final time=time when annual collar stops making impression on the mould.
- The final setting time of cement of OPC cement is 600 minutes (i.e. 10 hours).
Precaution for Initial and Final setting time of cement test
- The needle should be cleaned after every use.
- The mould should be slightly moved so that the penetration would not be at the same place.
- The experiment should be carried out at a place where there is no external vibration or disturbance.
- The mould should not have any type of movement from initial setting time to final setting time.
- The temperature of the room in which the experiment is conducted should be maintained around 27º-29º C and hydration should be maintained in between 60-70%.
I hope this post remains helpful for you.
Happy Learning – Civil Concept
Contributed By–
Civil Engineer – Sushmita Niraula
Read Also,
Fineness test of cement | Formula with Table of Calculation
Different grades of cement- IS Codes, Compressive Strength, Uses
17 Types of cement used for construction of the structure
Difference between OPC and PPC Cement- Strength, Grade, Durability
