Interior Plasters

Definitions:

Setting time: the period of time that elapses from the beginning of mixing of cement and water (zero time) until the material hardens.

Initial setting time: the time that elapses from pouring the cement into the water (zero time) until the time when the distance between the needle and plass plate is 6 mm ± 1 mm.

Final setting time: the time that elapses from zero time to the time when the needle has penetrated the hardened cement paste only to a depth of 0.5 mm.

Worksheet Task No. 3

Test Results:
Initial setting time is the time that elapses from the zero time till the time when the needle penetrates the specified depth of 6 mm ±1 mm. It is read every other minute. It is assessed whether the time meets the standard requirements. Final setting time is the time that elapses from zero time till the time when the needle has penetrated the hardened cement paste only to a depth of 0.5 mm. It is read every five minutes.

Vicat apparatus: the plunder is replaced with a cylindrical steel needle with an effective length of at least 45 mm and a diameter of 1.13 mm ± 0.05 mm
The total mass of the moving part must be 300g ± 1g. It shall move vertically and without significant friction and its axis shall be equal to the axis of the needle.
Before the test, the Vicat apparatus, which is equipped with a needle, is adjusted so that the needle, placed in a test bowl, is placed on the glass plate while the indicator is set to the zero scale mark. Then the needle is raised to the starting position.

Vicat ring: it is filled with the tested paste; the Cicat ring must be made from hardened rubber, plastic or brass. The ring has a conical shape, a depth of 40.0 mm ± 0.2 mm and an inner diameter of 75 mm ± 10 mm.

Test sample: cement paste with standard consistency (prepared and tested in a laboratory, which must have a constant temperature of 20° C ± 2° C and a relative humidity of at least 50%.

Methods

Determination of the setting time

The Vicat ring, placed on glass plate, is filled with a cement paste with standard consistency.
Then the Vicat ring is placed under the Vicat apparatus; the needle is carefully lowered in order to touch the surface of the cement paste. The needle shall remain in this position for 1-2 s.
Then the movable rod is quickly released, so that the needle penetrates vertically into the cement paste. The depth of penetration is read on the scale when the needle no longer penetrates the paste, but no later than 30 s from the release of the needle.
The readings are entered in the test report together with the time that has elapsed since the cement was poured into the water.
The puncture tests are repeated on the same sample of cement paste at suitably selected intervals of time ( e.g. in 10 minutes and at suitable points at least 8 mm from the edge of the ring or 5 mm from each other and 10 mm from the last injection).
The test specimen shall be stored in order to determine the final setting time.

Test result

The time that has elapsed from zero time till the time when the distance between the needle and the glass plate has reached 6 ± 3 mm. The resulting time is rounded to 1 minute.
An assessment of whether the observed time meets the standard requirements is carried out.

The initial setting time occurred …………… a minute  after zero time.

Cement …………………………… … (complies – does not comply)

The onset of solidification occurred …………… minutes from zero time.

Cement …………………………… … (complies – does not comply)

Determination of the final setting time

The filled Vicat ring, used to determine the initial setting time, is inverted so that final setting time determination tests can be performed on the side originally adjacent to the substrate. The Vicat ring is placed under the Vicat apparatus; the needle is carefully lowered in order to touch the surface of the cement paste. The needle shall remain in this position for 1-2 s.

Then the movable rod  is quickly released, so that the needle penetrates vertically into the cement paste. The depth of penetration is read on the scale when the needle no longer penetrates the paste, but no later than 30 s from the release of the needle.

The puncture tests are repeated at suitably selected intervals of time ( e.g. every 30 minutes).

The test specimen shall be stored in order to determine the final setting time.

In the time between the individual injections, the filled Vicat ring is stored in a test container in a storage room. The Vicat needle is cleaned immediately after each injection.

The final setting time is reached when the circular extension on the needle no longer leaves impressions on the surface of the test sample. The final setting time should also be confirmed by repeated injections at two other sides.

Test results

The time that has elapsed from zero time till the time when the needle has penetrated into the hardened cement paste only to a depth of 0.5 mm. The time is rounded to 5 minutes.

The final setting occurred ………… minutes from zero time.