How to Calculate Cement, Sand Quantity for Plastering?

Required volume of Cement Mortar = plastering area x plastering thickness = 100 x 0.012 = 1.2 m³

Adding Bulking of Sand & Wastage

So to get 1.2 m³ of wet cement mortar, we have to multiply the dry volume by 1.55.

What is 1.55 constant in the calculation?

1. Bulking of Sand – If the moisture is present in the sand, then it makes the sand look bulkier, which could result in inadequate sand proportion in the concrete ratio.

For Example, If we need to add 1m³ sand in the concrete mix ratio, we take 1.3 m³ (30% more). The reason for that is the moisture content present in the sand makes it a little bulkier. The 5% to 8% of surface moisture will increase the bulking of sand up to 20% to 30%. When we add more water (more than 8%) to the sand, the thin film will disappear, and volume decreases.

2. Wastage – Adding 20% wastage for joints and impressions filling

So if we need 1 m3 of cement mortar in wet condition we have to take consideration of the bulking of sand & wastage as (34%+20%) = 54%

Thus every time you need to calculate the volume of cement mortar you need to add the above percentage with dry volume

Wet Volume of concrete = Dry Volume of concrete + 54% of dry volume of concrete or

Wet Volume of concrete = Dry Volume of concrete x 1.54

So whatever volume we get from the above formula, we need to multiply the value with 1.54%

So total part of mortar = 1+3 = 4

Therefore,

• Required Volume of Cement = 1/4 x 1.55 (Bulkage & Wastage) x Mortar Volume

 = 1/4 x 1.55 x 1.5= 0.581 m³

To convert into cement bags  – (0.581 x 1440)/50 = 16.7 Bags

Unit weigh of Cement – 1440 Kg/m³    1 bag cement – 50 Kg

• Required Sand Volume = 3/4 x 1.55 (Bulkage & Wastage) x Mortar Volume

= 3/4 x 1.55 x 1.5 = 1.74 m³