Complete Guide on Consistency of Cement | Procedure | Calculation | Vicat Apparatus Test

What is the consistency of cement?

Consistency of cement is defined as the term which is used to indicate the degree of fluidity or degree of mobility of cement or else it’s defined as the amount of water that is needed to be added to the cement for obtaining standard consistency. Less amount of water added to the cement will not complete the chemical reaction and results in a reduction of strength.

So correct proportion of water to cement is to be known to achieve maximum strength while using the cement in any structure. The normal consistency of cement depends on various factors like the temperature and fineness of the cement. When the temperature increases the fineness and cement will give higher consistency.

Why do we use the consistency test of cement?

The main purpose of the consistency test of cement is to determine the percentage of water required for preparing cement pastes for other tests. Standard consistency is used for finding the setting time, final setting time and soundness of cement. The standard consistency of cement is defined as the consistency which will permit a Vicat plunger having 10mm diameter and 50mm length to penetrate to a depth of 33-35 mm from the top of the mould.

The Apparatus used is called Vicat Apparatus. Using Vicat Apparatus the percentage of water required to produce a cement paste of standard consistency can be found. The Standard Consistency of cement paste is also called Normal Consistency.

And also the cement used by different companies may not be of the same properties and there is a need to standardize the consistency using standard equipment. And also the consistency of cement has a remarkable effect on other properties of cement and it is necessary to check the consistency of cement.

Procedure for finding consistency of cement

Vicat Apparatus Test

The standard consistency of cement is calculated using the Vicat Apparatus. It consists of a frame that is attached to a movable rod weighing 300gm with 10mm diameter and 50mm length. There is an indicator attached to the movable rod for measuring the penetration of the rod. The mould used for placing the cement is a cylindrical one with 80mm diameter and 40mm height. (Fig.1)

This experiment must be carried out a room temperature between 20 and 27⁰C.

The other apparatuses used in the test are weighing balance, trowel, measuring glass, clean platform to make cement paste.

• 500gms of cement is taken and a paste is made with the weighted quantity of water for the first trial
• The paste made then is filled into the Vicat mould within 3 to 5 minutes and that time is known as the gauging time.
• The mould is then shaken to expel air
• A standard Plunger of 10 mm diameter and 50mm length is attached to the Vicat apparatus
• And it is released into the sample mould to make it sink into the paste by its weight
• The reading is taken by measuring the depth of penetration of the plunger
• The second trial is conducted by increasing the quantity of water added to the cement to make the paste
• The trials with increasing water-cement ratios are carried out till the penetration reaches a depth of 33 to 35 mm from the top
• The percentage of water that allows the plunger to penetrate only to a depth of 35 to 35 mm from the top is known as the percentage of water required to produce a cement paste of standard consistency (denoted by P)

Fig. 1: Vicat Apparatus and Plungers

Also Read: Various Tests on Cement

Calculation of Cement Consistency

Consistency = Percentage of water content when the depth of penetration is between 33 to 35 mm

\[\text{Standard}\ \text{Consistency}=\frac{\text{Weight}\,\text{of}\,\text{water}\,\text{added}}{\text{Weight}\,\text{of}\,\text{cement}}\times 100%\]

Consistency can also be calculated by plotting a graph between the amount of water added and the depth penetration. And by determining the amount of water required for 10mm penetration.

Also Read: Manufacturing of Cement By Dry and Wet Process

FAQs on Consistency of Cement