Initial And Final Setting Time Of Cement Test

Contents

What Is Initial Setting Time Of Cement?

The time elapsed between when water is introduced to the cement and when the cement paste begins to lose its fluidity is known as the initial setting time of cement.

Alternatively, it may be described as the period between adding water to the cement and the Vicat square needle penetrating a depth of 33-35 mm from the top (5 to 7 mm from the bottom) of the Vicat Apparatus’s mould.

What Is Final Setting Time Of Cement?

The interval between when water is introduced to the cement and when the cement paste has totally lost its fluidity is known as the final setting time of cement.

The amount of time after the water has been added to the cement and the square needle has made an impression on the paste, while the annular collar has failed to do so.

Apparatus Required

• Vicat’s apparatus: IS5513-1976 should be followed while using Vicat apparatus. It comprises a system to hold a 10 mm diameter plunger and two additional needles that are free to fall into a mould filled with cement paste. The three needles’ penetration can be monitored using vertical graduations ranging from 0 mm to 50 mm.
• Balance: At a load of 1000 g, the allowed deviation in balance in use is 1.0 g. On a fresh balance, the permitted variance is one-half of this figure. The reciprocal of the sensitivity must not be more than twice the permissible variation.
• Measuring cylinder stopwatch
• Glass plate
• Enamel tray
• Trowel

Procedure Of Initial Setting Time Test

1. Mix water and 0.85 percent cement by weight to make a cement paste.

2. The time it takes to mix should be between 3 and 5 minutes.

3. Pour the paste into the vicat mould properly and level the top surface.

4. Put the mould beneath a square needle, which is gradually lowered until it touches the paste’s surface.

5. Now release the square needle abruptly and allow it to sink into the cement mixture independently.

6. Measure the square needle’s penetration depth in the paste and record it.

7. Repeat the experiment with increasing time intervals until the square needle is pierced to a depth of 33 to 35 mm from the mold’s top.

8. The Initial Setting Period of cement is the time between adding water to the cement and the square needle penetrating a depth of 33 to 35 mm from the top of the mould.

8. In the case of Ordinary Portland Cement (OPC), the first setting time should be at least 30 minutes.

Procedure Of Final Setting Time Test

1. Add water 0.85 percent by weight of cement to make a cement paste.

2. The time it takes to mix should be between 3 and 5 minutes.

3. Now pour the paste into the Vicat mould and level its top surface.

4. Put the mould beneath a square needle with an annular collar lowering it to the paste’s surface.

5. Release the square needle with the annular collar abruptly, allowing it to produce an impression on the cement paste by its own weight.

6. This square needle with an annular collar leaves a mark that you can see.

7. Repeat the experiment with increasing time intervals until the square needle, but not the annular collar, makes an impression on the paste.

8. The Final Setting Period of the cement is the time between adding water to the cement and the square needle making an impression on the paste while the annular collar fails to do so.

9. For Ordinary Portland Cement (OPC), the ultimate setting time should not exceed 600 minutes.

Test Results

Initial setting time: Note the time when the needle fails to penetrate 5–7 mm from the bottom of the test block during the initial setting time of the cement. The initial setting time of cement is defined by this time.

Final setting time: Note the period when the needle fails to produce an impression on the test block’s surface. The final setting time of cement is defined by this time.

Criteria for Acceptance: The following are the results recommended by standard recommendations for various types of cement and their setting times:

Suppose your test value differs from the recommended result. In that case, there could be many causes for this, including a change in chemical composition during production (manufacturing defect), a problem in the testing device, or a testing error.

In that situation, you’ll have to be careful about the timing of your task. If the first setting time is shorter than this figure, the entire operation, including mixing, transporting, and placing, will complete within the time limit; otherwise, the cement paste/concrete/mortar will begin to set.

If the ultimate setting time exceeds this figure, scaffolding and form sides must be retained until the cement paste/concrete/mortar is entirely stiff, and the curing must be started carefully.

Importance Of Initial & Final Setting Time Of Cement

The cement mustn’t lose its fluidity too soon or too late. There is inadequate time for transportation and placement of concrete if cement sets too early.

If the cement sets too late, the construction work will delay. Additionally, the concrete will not achieve adequate strength quickly enough, causing the formwork removal operation to be delayed.

The amount of time it takes for cement paste to harden to a particular consistency.

It is linked to the aluminum–silicate combination formed by the chemical reaction of cement with water.

The initial setting time is crucial for concrete transportation, placement, and curing.

The initial setting time is also used to prolong the hydration or hardening process.

The final setting time is used for the safe dismantling of scaffolding or forms.

Factor Affecting Initial And Final Setting Time Of Cement

Cement composition, water-cementitious material ratio (w/cm), temperature, and admixtures are the main elements influencing the time it takes for concrete to be set.

Setting time is lowered when cement hydrates more quickly. As the w/cm ratio rises, the time it takes to set rises as well.

As the temperature rises, the time it takes to set drops. Additives can speed up or slow down the setting process depending on the kind.