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Building Design

How to Estimate the Quantity of Cement That Should Be Used in Concrete Plastering?

To come upon the required quantities of Cement, Sand & Water required for covering project, need to understand well on what features these quantities depend on. a. Quantity of Sand required: Quantity of Sand required depends upon the area of plaster work to be done and its width. It is also dependent on how much plastering material will be required for this area

b. Degree of dry density volume of Sand & Water: Dried density volume of Sand & Water is basically the amount of cement needed per square meter. In most cases, it is better to select dry-density products for more pliable plastering surfaces and cleanliness. However, when the surface to be plastered has some joints or slits in it, wet-density products are preferable to avoid the slipping of the paste into the recesses.

c. First and second coat ratio: This indicates how much cement is required for a particular area of work. Generally, it is in general advised that the first layer of plastering compound is applied on the surface that needs to be covered and then the second coat of cement applied on the bare surface. In some situations, where the surface to be plastered does not have any joint or slits in it, only the top coat is applied. Hence the total required first and second coat ration is different. It is generally advised that the first coat should be thin and translucent, while the second coat should be thick and durable.

d. Sand & Water required for Drying: The sand used in wet-drying processes is very fine because fine sand particles tend to cling to other fine particles like cement or sand. Therefore, too much sand or water can make the finished surface look lumpy. If excess mixture is applied, then the entire plaster will not be dry until the sand and water mixture completely dried up. To determine the proper cement quantity needed, you should determine how much sand and water the surface requires to become totally dry.

e. Total Volume of the Plasters: The total volume of the plaster is calculated by dividing the total volume of the cement by the total volume of the plaster. Note that this calculation only includes plaster surfaces that are being wet-dried. For dry-dried plaster, calculate the dry weight of each batch of plaster and divide it by the number of coats in a batch. Then multiply the result by the number of coats in a batch.

f. Secondary Coating thickness: This refers to the thickness of the coating on the interior surface of the plaster after the plaster has been mixed and thoroughly mixed with the cement. The main difference between first and second coat is the amount of cement used. The first coat is usually less than the second coat. Generally, the second coat is three times stronger than the first coat for ordinary plastering.

g. Rubber Quotient: The rubber quotient is the value used to measure the thickness of a thin layer of plaster. It is measured in grains. For thin wall and ceiling plastering, the value of the rubber quotient is usually in grams. In order to determine the value of the thickness of a second coat of plastering, you should multiply the thickness of the first layer of plastering by two.

h. Exterior Wall Condition: Before doing any concrete plastering, it is important to check the condition of the exterior walls of your home. You can do this by looking at the condition of the walls for cracks, chips, and other damage. You will need to use high quality cement paste for repairing any damage in the exterior walls before starting the process of plastering. If there are significant damages on an exterior wall, you should hire a professional contractor. You can also do it yourself but the result may be sloppy and uneven.

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