Consistency test of cement | Standard or Normal consistency, hi guys in this article we’ll know about consistency test on cement and normal or standard consistency test of cement. As you know standard or normal consistency test of cement is done by Vicat appartus with Plunger.
Consistency is defined as the way in which a substance holds together; thickness or viscosity. When we mix water in cement, it provides perfect uniform viscosity yet it is good for construction work. As we know cement is made of fine particle, so all the particles of cement are held between water particles together and make a uniform paste of cement.
Generally cement consistency test is done by Vicat appartus consist of Vicat instrument, mould cement specimen,plunger, weight balance and water measuring cylinder.
Consistency of cement is defined as minimum quantity of water added in cement to form uniform paste that provide sufficient viscosity and desirable strength for different type of structural work. Adding less or excess amount of water in cement causes reduction in its strength.
In this article we study about normal or standard cement consistency test by Vicat appartus, let us now discuss one by one.
What is Consistency of Cement?
A minimum quantity of water (in percentage) added to cement that initiate the chemical reaction between water and cement to form a uniform paste of sufficient viscosity and desirable strength is known as consistency of cement.
Consistency test of cement is done by Vicat appartus consist of Vicat apparatus, Plunger, Vicat Mould, scale and weighing balance, measuring cylinder and glass plate.
● 1) Normal or Standard Consistency of cement – the minimum quantity of water required for cement to form uniform paste that provide sufficient viscosity which will allow the Vicat plunger to penetrate to 5-7 mm point from the bottom and 33 -35mm from top of Vicat cement mould according to standard condition of temperature and humidity is known as cement normal or standard consistency.
Now question is “What is Standard or Normal consistency of cement? Their answer will be following:
The standard or normal consistency of ordinary Portland cement varies between 25-35%.
Why normal or standard consistency of cement varies?
Normal or standard cement consistency varies because of weather conditions, temperature, humidity, excessive composition of silica in cement, fineness of cement and we know that cement are provided and made by different companies have some different consistency.
Importance of Cement Consistency
As we all familiar that strength of concrete and cement mortar depends on water cement ratio, so right amount of water percentage is necessary in the concrete mix to gain accurate strength. the quality material used in concrete and cement mortar, Cement is one of them. In order to attain the required sufficient cement strength, we need to add the right amount of water.
Water less than the Normal or standard consistency would not initiate the chemical reaction between water and cement resulting reduction in the strength of cement. excess or less percentage of water added to cement resulting strength reduction. That’s why it is important to know the standard consistency of cement.
Why is Consistency Test of cement Done?
We know that the cement we used on our site is mostly affected by Weather Conditions temperature and humidity, Excessive composition of Silica. Silica is one of the cement ingredients which determines the initial and final setting time of cement paste and The fineness of cement.
By Standardising the consistency of cement, we know that how much of water is required to produce an effective cement viscosity which will eventually produce good quality of cement mortar and concrete. For calculating the exact quantity of water percentage should be added with cement to perform good concrete, cement consistency test should be done.
Standard Consistency of an ordinary Portland cement varies between 25-30%. That means we need minimum 25% of water and maximum 30% in volume to make a standard consistency of cement paste.
For Example, If we need to calculate the amount of water required for a 300 g of cement which has minimum 25% consistency means then we need 25% of 300g = 75g water minimum and maximum 30% of 300 = 90g to prepare a standard consistency of cement.
Consistency test of cement with Vicat Apparatus
Let us do the Lab test, how to find normal or standard cement consistency. All the test should be done at Standard method:
● 1) Environment factors: should be done at normal condition of weather, temperature should be 27 +_ 2℃ (25℃ or 29℃) and humidity should be 90% about, these are the two important environmental factor which are responsible for standard consistency calculation.
● 2) Objective of cement consistency test:The Aim of this consistency test is to find the basic required percentage quantity of water to form a cement paste of uniform viscosity according to specified by IS Code 4031 (Part 4 – 1988) which the Vicat Plunger will penetrate in Vicat mould specimen of cement to 5-7mm point to the bottom or 33-35mm from top of Vicat mould.
● Apparatus Required:
1) Weighing Balance of 1000 gram with 0 gram error accuracy.
2) Measuring Cylinder of 200ml for measuring of water quantity
3) Vicat Apparatus consist of glass plate, scale, cap load and plunger and Vicat mould. Genera Plunger should be 50mm height and 10mm dia and vicat mould size is 80mm dia and 40mm height.
Cement consistency Test procedure
Now do the Test procedure to find out normal or standard cement consistency in following steps:-
1) take fresh quantity of 300 gram of cement and place it in bowl or tray.
2) assume standard consistency 25-30% of water, measure 75g -90 g of water
3) first we mix 75g (25%of cement) of water in cement and mix properly, if cement paste is not uniform then add extra amount of water increasing up to 30%. Care should be taken that cement paste should be ready in just 3 to 5 minute, the time taken to obtain cement paste after adding water is also known as gouging time.
4) now fill the cement paste in Vicat mould upto the level, and care should be taken that remain part of excessive cement paste taken off by using towel.
5) now put The Vicat mould specimen on glass plate centrally to the direction of plunger just below.
6) now release the plunger to penetrate cement mould specimen after few second measurements of depth of penetration should be done. Note down the reading on the Vicat measuring scale
● Result of cement consistency test: At about 28% of water quantity of cement are sufficient to form cement paste which allow the Vicat Plunger will penetrate in Vicat mould specimen of cement to 5-7mm point to the bottom or 33-35mm from top of Vicat mould. So consistency of cement is 28%.
● Precautions of Test procedure: The Test should be conducted at Room Temperature. The humidity of the room should be 90% and temperature should be 27+_ 2℃. The whole process of mixing should be made on Glass Sheet.
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