Cement is an unavoidable part of construction, it is essentially a glue that sticks all other components of construction together. And for that reason, the cement you use in any construction needs to be of good quality so that your structure stays strong. Making use of consistency tests is one way you can know how good your cement is.
When it comes to cement, consistency is the degree of fluidity or stiffness of the cement paste. This consistency is responsible for the strength, setting time, and overall performance of the cement in construction. There is a standard level of consistency called “normal consistency” that is easy to mix, place, and finish. You usually require water that is 25% to 30% of the weight of the cement. But the exact amount can differ depending on the type of cement and its properties
The right water-cement ratio is also responsible for giving the cement paste optimum strength and durability. Even while using the best TMT steel bars, the cement must be of good quality. Then there is the matter of the setting time. The cement is also set at the right pace if it has normal consistency. If there is too much water, the paste becomes too runny and takes too much time to set. On the other hand, if there is not enough water, it can become hard too fast and set at the wrong time.
Before starting construction, experts make use of this cement consistency test to guarantee the project’s performance and quality. By ensuring that the cement does not fracture or become weak, it can prevent different types of failures. In the long term, taking precautions to prevent any predicted problems and delays can also help you save time and money. Also, if everyone adheres to the standard consistency in all batches, it will be easier to maintain the same quality throughout the structure
Consistency Test of Cement Procedure
There are some specific steps and procedures you need to follow along with the right equipment to get accurate results. Here is a simple breakdown of the whole process.
Material required to perform the test :
Vicat apparatus which includes a mold, a plunger that is 10mm in diameter, and a measuring scale
Weighing balance that helps measure the quantity of cement and water with utmost accuracy
Mixing pan that can mix the cement and water to make the paste
Trowel/ Spatula that is used to mix and fill your mold
Cement Samples that can be used for testing. Typically you would require 300 grams of cement for this
Water that is clean and fresh
Use a weighing scale to measure out 300 grams of cement
Now we need to add water to it. You can start by adding 75 grams of water which is 25% of the weight of the cement. This is just an initial estimate. You will need to adjust the water content according to the results you obtain from the tests.
Use a trowel or spatula to mix the water and cement in the mixing pan thoroughly. Mix until you get a smooth and homogeneous past without any lumps
Place the Vicat mold on a solid surface and pour the cement paste into it. Use the trowel or spatula to pat down the cement and get rid of all the air bubbles. This process will also make sure that the paste is evenly packed
Place the mold under the plunger of the Vicat apparatus. Make sure that when you place it, the plunger touches the surface of the cement paste.
Release the plunger so that it comes down and penetrates the cement paste under its weight
You can observe and measure how far the plunger penetrates the paste. This can be read from the scale on the apparatus.
The desired range is 5 to 7 mm from the bottom of the mold. If you do not get the desired range, repeat the test by adjusting the water content in the paste. If the penetration is low, that means the cement is too thick and you need to add more water. If it is too deep, then it means that the paste is too thin and you need to reduce the amount of water you use.
Once you get optimum penetration, record the amount of water used. This is the adequate amount of water that is required to get normal consistency.
