Question

The cement consumption per 100 sqm area for 12 mm thick plastering with cement mortar proportion of (1: 4) is
1. 18 bags
2. 15 bags
3. 12 bags
4. 9 bags

Answer 1

Correct Answer - Option 3 : 12 bags

Concept:

Plastering:

Plaster is a thin layer of mortar applied over the masonry surface and it acts as a damp-proof coat over the brick masonry work. Plastering also provides a finished surface over the masonry that is firm and smooth hence it enhances the appearance of the building. Plastering usually 12 mm thick is calculated in a square meter. 

For calculation of plastering work:

• Volume is increased by 30 % due to uneven surface
• Now increased by 25 % in calculated volume for dry volume
• Bulk density of cement = 1440 kg/m3
• Weight of 1 bag of cement = 50 kg 

​Calculation:

Area to be plastered, A = 100 m2

Thickness of cement plastering = 12 mm

Volume of wet mortar required, V = 100 × 0.012 = 1.2 m3

Volume is increased by 30 % due to uneven surface,
= 1.2 × 1.3 = 1.56 m3

Now increased by 25 % in calculated volume for dry volume

Dry volume = 1.56 × 1.25 = 1.95 m³

Cement: Sand is 1: 4 

\({\rm{Volume\;of\;Cement}} = \frac{1}{{\left( {4 + 1} \right)}} × 1.95 = 0.39 \ {{\rm{m}}^3}\)

Weight of the cement = Volume of the cement × Density = 0.39 × 1440 = 561.6 kg

Cement bags required = \(\frac{561.6}{50}\) = 11.23 = 12 bags.