  ## What is the quantity of steel (kg) required for the construction of a building?

Steel quantity or consumption is dependent on the following things,

• Purpose of building (Residential, Commercial, Institutional or Industrial/Plant)
• Type of structure (Load Bearing, Framed type: Low Rise or High Rise)
• RCC members of building (Beam and Column spacing)
• Design methodology to be adopted depending upon Seismic Zones (Zone I to V)

But, still there is a thumb rule for RCC buildings which provides approximate quantity of steel per cubic meter of concrete

• For Footings the amount varies in the range of 80kg  to 90kg per cubic meter
• For Slabs the amount varies in the range of
80kg  to 100kg per cubic meter
• For Beams the amount varies in the range of 110kg to 120kg of per cubic meter
• For Columnsthe amount varies in the range of 150 kg to 180 kg per cubic meter

## How to calculate the steel quantity?

• Study the RCC drawing and prepare a bar bending schedule which would let you know steel or reinforcement diameter wise.
• Use the formula d x d/162 where, d is the diameter of the bar and multiply it with the total length of the bar.
• Length of Bar = Length of Member – Cover
• Sum up all the quantities and you would achieve or get the required quantity in kg.

Following are the weight of different diameter of bars

6 mm = 6 x 6 / 162 = 0.22 kg per running meter length similarly,
8 mm = 0.39 kg per running meter length
10 mm = 0.62 kg per running meter length
12 mm = 0.89 kg per running meter length
16 mm = 1.58 kg per running meter length
20 mm = 2.46 kg per running meter length
25 mm = 3.86 kg per running meter length

## What is the quantity of cement, aggregate and sand (kg) required for 1 cubic meter of concrete?

Concrete is a composite mixture of Cement, Sand and Aggregate. Concrete mix design is the procedure for finding the right quantities of these materials to achieve the desired strength. In order to calculate or find the right amount of cement, sand and aggregate required in 1 cubic meter of concrete, you need to know different grades of concrete.

As per IS456:2000, Different grades of concrete are classified into  M5, M7.5, M10, M15, M20 etc., where, M stands for Mix and the number stands for Characteristic Compressive strength(fck) of the concrete in N/mm2 @28 days when checked with 150mm×150mm×150mm cube in direct compression test.

The procedure for finding the different grades of concrete mixes is same. The below illustrated method is for concrete mix design of M20 grade.

The concrete mix ratio for M20 grade of concrete is 1:1.5:3 that mean 1 part of cement, 1.5 part of sand (fine aggregate) and 3 parts of aggregate (crushed stone) in volume and then batched for mixing.

Concrete Mixes are primarily divided into the two different types:

Nominal Mix: Nominal Mix is generally adopted for low rise construction activities. In this type, the mix ratios and concrete constituent proportions are prefixed and specified. i.e., M20 (1:1.5:3),  the quantity of cement, sand and aggregate is volume batched as per the fixed ratio 1:1.5:3.

Design Mix: Design mix concrete is adopted for high rise constructions activities. In this type of mix, the mix ratios are decided by Engineer after analyzing the properties of individual ingredients of concrete. There is No pre-fixed ratio and ingredients are weigh batched.

To calculate the individual quantities of cement, sand and aggregate required for 1cubic meter assume a nominal mix grade of concrete such as M20.

As per IS 456:2000 M20 Grade concrete proportion is equal to1: 1.5: 3

We have to add all the volume to know the total volume which is equal to 1 + 1.5 + 3 = 5.5

We know that during concreting when wet concrete is poured, it gets harden after certain standard time (i.e., 30min per IST). To counter that shrinkage a factor of safety ranging from 1.54 to 1.57 can be assumed or considered.

i.e., volume of dry concrete = 1.54 to 1.57 times volume of wet concrete

Let’s assuming1.54 as factor of safety

So total volume of concrete required is 1.54 cubic meter

Calculation of Volume of Cement in 1cubic meter of Concrete:

To calculate the Quantity of Cement in Concrete the following formula is used.

Volume of Cement = Cement⁄ Ʃ (Cement + Sand + Aggregate) x 1.54

= 1 / (1 + 1.5 + 3) x 1.54

= 0.28 cubic meter

(Density of Cement = 1440 kg per cubic meter)

Quantity of cement = Volume x Density

= 0.28 x 1440 = 403.2 kg

For 1m3 of Concrete = 403.2kg of cement is required.

Number of cement bags (i.e., 50 kg each) required for 1m3 of Concrete

= 403.2/50 = 8.06 say 8 bags

Calculation of Volume of Sand (Fine Aggregate) in 1cubic meter of Concrete:

To calculate the quantity of sand in concrete the following formula is used.

Volume of Sand = Sand ⁄ Ʃ (Cement + Sand + Aggregate)    x 1.54

= 1.5 / (1 + 1.5 + 3) x 1.54

= 0.42 cubic meter

(Density of Sand = 1602 kg per cubic meter)

Quantity of sand = Volume x Density

= 0.42 x 1602 = 672.84 kg say 673 kg

Calculation of Volume of Coarse Aggregate in 1cubic meter of Concrete:

To calculate the quantity of coarse aggregate in concrete the following formula is used.

Volume of Coarse Aggregate

= Coarse Agg. ⁄ Ʃ (Cement+ Sand+ Aggregate) x 1.54

= 3 / (1 + 1.5 +3) x 1.54

= 0.84 cubic meter

(Density of coarse aggregate = 1550 kg per cubic meter)

Quantity of Coarse aggregate

= Volume x Density

= 0.84 x 1550 = 1302 kg

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