Replacing 10 mm bars with 12 mm bars in RC slabs

To determine the spacing of 12 mm bars when replacing 10 mm bars in a reinforced concrete (RC) slab, we need to consider the following factors:

1. Find the area of steel reinforcement:
- The area of steel reinforcement is determined by multiplying the cross-sectional area of each bar by the number of bars.
- For 10 mm bars, the cross-sectional area is π(10/2)^2 = 78.54 mm^2.
- Let's assume the original slab had a certain number of 10 mm bars, so the total area of reinforcement can be calculated by multiplying the area of one bar by the number of bars.

2. Calculate the area of reinforcement for 12 mm bars:
- Since we are replacing the 10 mm bars with 12 mm bars, we need to determine the number of 12 mm bars that would provide the same area of reinforcement.
- The cross-sectional area of a 12 mm bar is π(12/2)^2 = 113.10 mm^2.
- Dividing the total area of reinforcement by the area of one 12 mm bar will give us the required number of 12 mm bars.

3. Determine the spacing of 12 mm bars:
- The spacing of the 12 mm bars will depend on the total length of the slab and the number of bars.
- Assuming the spacing between the 10 mm bars was 10 cm, we can determine the required spacing for the 12 mm bars.

Calculation:

Let's assume the original slab had a total area of reinforcement represented by A1 (mm^2).
The area of reinforcement for the 10 mm bars can be calculated as:
A1 = (π(10/2)^2) × Number of 10 mm bars

Since we are replacing the 10 mm bars with 12 mm bars, the required number of 12 mm bars can be calculated as:
Number of 12 mm bars = A1 / (π(12/2)^2)

Assuming the spacing between the 10 mm bars was 10 cm, the spacing for the 12 mm bars can be calculated as:
Spacing of 12 mm bars = Total length of the slab / Number of 12 mm bars

Therefore, the correct answer is option 'C' - 14.40 cm.