We have already talked a lot about the properties of Cement and conducted some tests.
Today we are going to see the consistency of cement test.
What is Consistency of Cement?
A Minimum quantity of water required to initiate the chemical reaction between water and cement to form a paste is known as consistency of cement.
Standard Consistency – It is that cement consistency which will allow the Vicat plunger to penetrate to 5-7 mm point from the bottom of Vicat mould is known as standard consistency.
Importance of Cement Consistency
As we all know the strength of concrete depends on the quality material used in it. Cement is one of them. In order to attain the required cement strength, we need to add the right amount of water.
Water less than the standard consistency would not initiate the chemical reaction between water and cement resulting in the strength of cement. Water more than the consistency result in excess water and strength reduction. That’s why it is important to know the standard consistency of cement material.
Why is Consistency Test Done?
We know that the cement we used on our site is mostly affected by
- Weather Conditions
- Excessive combination of Silica. One of the cement ingredients which determines the initial and final setting time of cement paste.
- The fineness of cement. We have discussed this in specific gravity of cement
- Manufacturing Defects
By Standardising the consistency of cement, we know that how much of water is required to produce an effective cement which will eventually produce good quality of concrete.
Standard Consistency of an ordinary Portland cement varies between 25-35%. That means we need 25% of water in volume to make a standard consistency of cement.
For Example, If we need to calculate the amount of water required for a 200 g of cement which has 30% consistency means then we need 200*30% = 60g water to prepare a standard consistency.
This is what we are going to find in this test.
Cement Consistency Test with Vicat Apparatus
The whole test is conducted in test and error method.
First, we assume some percentage as the standard consistency. We test it out against our Vicat apparatus.
The Aim of this test is to find the basic required quantity of water to form a cement paste as specified by IS Code 4031 (Part 4 – 1988) which the Vicat plunger will penetrate to 5-7mm point to the bottom of Vicat mould.
- Weighing balance of 1000g with 1g accuracy
- Vicat Apparatus
- Vicat Mould
- Measuring Cylinder 200 ml
- Glass Plate
- The Test should be conducted at Room Temperature.
- The humidity of the room should be + or – 65+
- The whole process of mixing should be made on Glass Sheet.
- Take 400 grams of Cement.
- Assuming that consistency would be 29.5% since we are taking OPC. This is trial and error method.
- Take 29.5% of water that means (400×29.5%) = 118 Grams of water.
- Mix the water with cement and wait for 3-5 Minutes.Mix the cement well as shown in the video.
- Now fill the Vicat mould with the cement paste.
- Ensure to compact the paste well after filling the mould.
- Fill the cement paste to the top of the mould. Remove the excess paste by the trowel.
- Now place the mould at the Vicat apparatus.
- Now remove the plunger and allow it to penetrate through the paste.
- After Removing wait for 3 seconds.
- Note down the reading on the Vicat measuring scale.
Consistency Test Video
- The test result should be – 5-7 mm measurement in Vicat apparatus.
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