Academics

Vicat Apparatus – Initial and Final Setting Time Of Cement


Vicat Apparatus is a device used to determine the consistency and setting time of cement. Consistency and setting time of cement are significant degrees of consideration for any cement water paste. As these helps in preparing a proper paste of cement which meets all the standard specifications. Vicat apparatus consists of a metallic frame, graduated scale with index, sliding probe of 300g, consistency plunger of 10mm, initial setting time needle of 1mm, an annular needle for final setting time calculation and non-porous plate, like glass base plate or stainless plate.

We also conduct a test of knowing the expansions or volume changes in cement, i.e., Soundness Test Of Cement by Le-Chatelier Apparatus. But before this, we also come to know the Sieve Test Procedure To Check Fineness Of Cement. As the fineness and soundness are very crucial for sustenance or otherwise the structure will not bear the heavy loads. A standard representation of the Vicat apparatus with standard dimension is shown below.

vicat apparatus

Aim

To calculate the initial and final setting time of cement by using Vicat apparatus.

Apparatus

i) Vicat apparatus
ii) Trowel
iii) Balance
iv) Measuring cylinder and
v) Stopwatch.

Theory

  • Cement in the presence of water indulges in the process of hydration. This hydration process is imperative in context to stiffening of cement. During the process of cement hydration form, a compound of aluminium silicate and the process continue until the cement completely hardens and takes the shape of the mould.
  • The initial setting of the cement is time duration time at which the cement start to stiffen to a defined consistency and loses its plasticity, Whereas the final setting time cement is the time duration at which the cement gets harden enough and takes the form of the mould.
  • The initial setting of cement is lies in between 30-60 minute, on the other hand, the final setting time lies in between 9-10 hours.

Procedure

(i) Prepare a paste of cement 400g with 0.85 times the water required for the consistency.
(ii) The gauging time should be a 3-5 minute.
(iii) After gauging properly filled it in the Vicat mould and level it with the help of trowel.

Initial Setting Time

1. For determining the initial setting of cement set the 1mm diameter needle to the lower end of the rod.
2. Immediately place the Vicat apparatus mould filled with cement paste above the non-porous glass plate.
3. Lowers the needle and allow it to penetrate into the mould.
4. Repeat the procedure till the needle fails to pierce the mould to a point  5.0 ± 0.5 mm measured from the bottom of the mould.
5. Now record the period between the water is added to the cement and the needle fails to pierce the mould by 5.0 ± 0.5 mm measured from the bottom (t2).

Final Setting Time

1. For determining the final setting of cement time set an annular needle to the lower end of the rod.
2. Repeat the same procedure for the final setting time as in initial setting time.
3. Lowers the needle and allow it until the annular needle makes an impression on the mould.
4. Now record the time period between the water is added to the cement and the annular needle fails to make an impression on the mould (t3).

Standard Specification

S.NO. Type Of Cement Referenced Indian Stanadard Initial Setting Time, mints (min. Final Setting Time, mints (max.)
1. OPC(33) IS:269 30 600
2. OPC(43) IS:8112 30 600
3. OPC(53) IS:12269 30 600
4. PSC IS:455 30 600
5. High alumina IS:6452 30 600
6. Super sulphated IS:6909 30 600
7. RHPC IS:8041 30 600
8. SRC IS:12330 30 600
9. Low heat IS:12600 60 600
10. PPC IS:1489,P1 30 600
11. Masonry cement IS:3466 90 1440
12. IRS-T-40 Railway 60 600

Calculation

Initial setting time = t2 - t1
final setting time= t3 - t1

where,
t1= time at which water is first added to the cement.
t2= time at which needle fails to penetrate the 5mm to 7mm mark from bottom of the mould.
t3= time at which needle makes an impression but fail to do so.

Precaution

  • The gauging time period should not be less than 3 minutes and not exceeds to 5 minutes.
  • Handle the apparatus of checking the initial and final setting of cement with care.
  • The position of the mould should be changed after every penetration so as avoid the penetration at the same place.
  • The reading should take properly and carefully.

Vicat Apparatus Uses

  • The Vicat apparatus is used to determine the consistency of cement under a defined water to cement ratio.
  • It helps in calculating the initial setting time of the cement so that the time period at which the cement paste losses it plasticity can be determined. It helps in determining the consistency of cement during its transportation to far off places.
  • It also helps in determining the significant time period for complete hardening of cement.
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