The diameter of needle used in Vicat's apparatus for the determination of initial setting time is prescribed as

Explanation:

The following table attachment of Vicat's apparatus for different tests

Additional Information

The Vicat Apparatus is used to determine the setting time and consistency of cement and other hydraulic binders.

It helps assess:

• Initial setting time: When the paste begins to stiffen.

• Final setting time: When the paste hardens sufficiently.

• Standard consistency (normal consistency): Water content required to prepare cement paste of a standard plasticity.

Components of Vicat Apparatus

• Frame with movable rod: Holds the plunger or needle.

• Plunger/Needles:

  • Plunger (10 mm dia, 50 mm long): for consistency test.

  • Initial setting needle: for initial setting time.

  • Final setting needle with annular collar: for final setting time.

• Graduated scale: Measures penetration depth.

• Mould (Vicat mould): Conical frustum-shaped mould, typically:

  • Top diameter: 60 mm

  • Bottom diameter: 70 mm

  • Height: 40 mm.

• Glass base plate: on which the mould is placed.