There are some unanswered questions which may be answered within a minute or within 2-3 sentences. Nobody specifically wants us to know or no one asks us in the interview. But it is our responsibility as a civil engineer to know every in and out of construction.
Why don’t we exclude steel volume in Concrete Calculation?
Whenever we calculate the concrete volume to cast structural members like a beam, footing or slab, we don’t actually exclude the steel reinforcement quantity.
Based on the thumb rule of steel quantity or by the exact calculation, the amount of steel used in structural elements is from 1-3%. It is very low compared to the concrete volume. So we will neglect that.
| Structural Element | Percentage of Steel in Concrete |
| Slab | 1% |
| Beam | 1% to 2% |
| Column | 2.50% |
For example, take the below slab, which is 2m X 3m X 0.125m.
V = L x B x DTherefore total concrete volume = 0.75 m3
According to the thumb rule, the required amount of steel for the slab is 1%
Therefore required steel quantity = 0.75 * 1% = 0.0075 m3 which is negligible.
This will be compromised in concrete wastage while pouring it. So we don’t exclude the reinforcement quantity separately.
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