The initial setting time of cement is the time when the cement paste begins to harden while the final setting time is the time when the cement paste is sufficiently hardened.
Importance of Initial and final setting time test of cement
- The setting should not be confused with tighter, which refers to the gain in mechanical strength after a certain degree of resistance to penetration of a particular attachment.
- The scheduled time is the time required to harden the cement paste to a defined consistency.
- Indirectly related to the initial chemical reaction of cement with water to form aluminum-silicate compounds.
- The initial setting time is the time when the paste begins to lose its plasticity.
- The initial setting time test is important for the transport, placing, and compaction of cement concrete.
- An initial setting time period is required to delay the hydration or hardening process.
- The final setting time is the time when the paste loses its plasticity completely.
- This is the time taken for cement paste or cement concrete to harden sufficiently and to obtain the shape of the mold in which it is poured.
- Determining the final setting time period allows the scaffolding or form to be safely removed.
- The primary chemical reaction of cement with water is almost complete during this period.
- It is necessary that the cement is neither set too fast nor too slowly. In the first case there may be insufficient time to transport and place the concrete before it becomes too rigid. In the second case, too, the duration of work is slowed for a long period, it may also postpone the actual use of the structure due to insufficient strength at the desired age
Testing Method of Initial and final setting time of cement
Test Standard : IS 4031-Part 5: 1988
- Weighing Balance of accuracy 0.01gm
- Vicat’s apparatus with needle and annular attachment
- Graduated glass measuring jar
- Gauging towels
- Maintained the laboratory at the temperature and relative humidity of 27±2oC and 65±5%.
- Take the representative cement sample to be tested and test sample shall be prepared by adding 300 gms of cement in evaporation dish.
- Mix the water of 0.85 time that is required to form a cement paste of standard consistency by the weight of cement.
- Start the stopwatch exactly when water has been added to dry cement. Care should be taken that the mixing time should not be less than 3 minutes or more than 5 minutes from the time of water adding dry cement.
Initial setting time
- Place the mould of the Vicat’s apparatus on a non-porous plate and fill the mould with the paste.
- After filling smoothen the surface of the paste, making it level with the top of the mould. Shake the mould slightly to expel the entrapped air.
- Place it below needle of Vicat’s apparatus and lower the needle gently to touch the surface of the test block.
- Quickly release the needle, allow it to sink into the paste and record the penetration of needle from the bottom of mould.
- If this is not between 5+/- 0.5 mm, allow it to remain there without any disturbances or vibrations and check the penetration into the cement paste at frequent intervals of time.
- Initial setting time is the time taken for the needle to have a penetration of 5=/- 0.5mm from the bottom of mould from the time of water added to the dry cement.
Final Setting time
- To assess the final setting time do not stop the stopwatch. Remove the needle and attach the needle with the annular attachment to the Vicat’s apparatus.
- Lower the needle with annular attachment gently to touch the surface of the test block. Observe the impression made by the needle with annular attachment.
- If the impression made is only by needle, the cement said to be final set, if not allow it to remain there without any disturbances or vibrations and check the impression made on the cement paste at frequent intervals of time.
- The final setting time is the elapsed time between the time the water is added to the dry cement when the needle makes an impression on the surface of the test block and the coil attachment fails to do so.
- Both the Initial and final setting time of cement shall be reported to the nearest 5 minutes.
- Fineness test of Cement by dry sieving method 90 micron sieve
- Soundness test of cement by Le Chatelier
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