Initial setting time of concrete is the time period between addition of water to cement till the time at 1 mm square section needle fails to penetrate the cement paste, placed in the Vicat’s mould 5mm to 7mm from the bottom of the mould. This test is required to understand the time cement takes for initial setting between mixing and transporting and placing of concrete.
Procedure to Find Setting Time of Cement
- Vicat’s apparatus
- Measuring cylinder
- Stop watch
- Glass plate
- Enamel tray
- Consistency test to be done before starting the test procedure to find out the water required to give the paste normal consistency (P).
- Take 400 g of cement and prepare a neat cement paste with 0.85P of water by weight of cement.
- Gauge time is kept between 3 to 5 minutes. Start the stop watch at the instant when the water is added to the cement. Record this time (T1).
- Fill the Vicat mould, resting on a glass plate, with the cement paste gauged as above. Fill the mould completely and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared is called test block.
- Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle.
- Lower the needle gently until it comes in contact with the surface of test block and quick release, allowing it to penetrate into the test block.
- In the beginning the needle completely pierces the test block. Repeat this procedure i.e. quickly releasing the needle after every 2 minutes till the needle fails to pierce the block for about 5 mm measured from the bottom of the mould. Note this time (T2).
ObservationsWeight of cement taken (g) = _________ Quantity of water added to cement = =0.85 X Quantity of water required for standard consistency in ml = _____ Time at which water is first added to cement (T1) in sec = _____ Time when needle fails to penetrate 5 mm to 7 mm from bottom of the mould (T2) in sec = _____
Initial Setting Time = T2-T1
ResultThe initial setting time of the given sample of cement= _____ min
PrecautionsSome necessary precaution taken while performing initial setting time test are,
- Release the initial and final setting time needles gently.
- The experiment should be performed away from vibration and other disturbances.
- Needle should be cleaned every time it is used.
- Position of the mould should be shifted slightly after each penetration to avoid penetration at the same place.
- Test should be performed at the specified environmental conditions.
Standard Specification of Setting Time for Different Type of CementDepending upon the admixtures added into the cement in the process of manufacture of cement, the setting time differs for different cement. Standard setting times are listed in the below table as per IS 4031, IS 269. Table-1: Setting Time for Different Type of Cement
|Cement Type||Initial Setting Time in Min As per IS Codes|