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HOW TO CALCULATE QUANTITY OF CEMENT REQUIRED FOR PLASTERING?

CEMENT MORTAR PLASTERING


Among different plastering methods like lime, cement, mud plastering, the cement plastering is considered as an ideal plastering method for external renderings. It is used and best recommended for damp conditions like
  • Ø  Bathrooms
  • Ø  Floors
  • Ø  Copings
  • Ø  Water Tanks
  • Ø  Areas where non-adsorbent surfaces are demanded





HOW IS CEMENT MORTAR APPLIED? 



The cement plasters are applied mainly in a single coat. In situations where the thickness of the plaster is more than 15mm, it is recommended to have a finer finish and have to be applied in two coats.
The table: 1 shows the details of the plaster in three coats with cement mortar


TABLE-1



CEMENT MORTAR PLASTERING RATIOS



Before you start to calculate the amount of cement and sand (cement mortar), you need to identify the purpose and hence the ratio for which the calculation has to be done. Some of the common cement mortar ratios for different plastering needs are mentioned below in Table-2.

TABLE-2

HOW MUCH CEMENT REQUIRED FOR ONE SQUARE METER OF PLASTERING?


The determination of cement for 1sq.ft of plastering area involves the following steps:


Step 1: Determine the Plastering purpose and Plastering Thickness


First, determine the area where you wish to plaster. Based on the purpose choose the plastering ratio, as in Table 1. These can vary based on the suggestion given by the engineer.


Step 2 : Calculation of Volume of Cement Mortar


For example: Let the area to be plastered be 100m2

Ratio of Cement Mortar = 1:6
Plastering Thickness = 12mm = 0.012m

Volume of the cement Mortar Required (V) = Plastering Area x Thickness
    V = 100m2 x 0.012 = 1.2m3

Here the volume obtained ‘ V ‘ is the wet volume. That means this must be the volume that we must get after mixing water. So to take into account for dry volume. Here we must account for:
Ø  Bulking of sand = 30 – 35%
Ø  Wastage = 20%

If we consider 35% extra and 20 %, the final volume Vfinal is

Vfinal = V + (35% of V + 20% of V) = V + (55% of V) = V+ 0.55V = 1.55V

As V = 1.2m3
Vfinal = 1.55 x 1.2 = 1.86m3

Step 3: Calculation of Cement and Sand From the ratio and the volume determined


Cement: Sand (ratio) = 1: 6
Total Parts = 1+6 = 7

Quantity of cement = (Parts of cement/ total parts) x Total Volume of Cement
                                                                                                        Mortar.
                                       = (1/7) x 1.86
                                  = 0.265metre cube
          = 0.265/.0347 = 8 bags (approximately)

(Because 1 cement bag = 0.0347 metre cube)


Quantity of Sand = (Parts of sand / total parts) x Total Volume of Cement Mortar
                                 = (6/7) x 1.86
                              = 1.59 metre cube


Step 4: Calculation of Cement and Sand for 1 metre square


For 100 square metres, we require 0.265 metre cube of cement and 1.59 metre cube of sand.
Then,
For 1 metre square = 0.265/100 metre cube of cement

           = 0.00265metre cube of cement
 .0159 metre cube of sand

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