Rain occurs during slab casting—what steps will you take? | Q & A

1. Stop or Control Concreting Immediately

• Stop concreting if rain is heavy

• If light rain:

  • Slow down the pour

  • Protect freshly placed concrete

Never allow uncontrolled rainwater to mix with concrete.

2. Protect Fresh Concrete

• Cover slab with:

  • Plastic sheets / tarpaulin

  • Polythene covers

• Prevent direct rain impact on surface

3. Prevent Change in Water–Cement Ratio

• Do not allow rainwater to:

  • Flow over slab

  • Collect on surface

• Remove excess surface water gently (sponge, squeegee)

4. Check Concrete Workability

• Re-check slump if concreting continues

• Do not add cement or water on slab to compensate

5. Ensure Proper Compaction

• Continue vibration carefully

• Avoid over-vibration (risk of segregation)

6. Construction Joint (If Pour Is Stopped)

If concreting must be stopped:

• Stop at a planned construction joint

• Level and roughen surface later

• Follow proper joint treatment before next pour

7. Safety Measures

• Stop work if:

  • Slab becomes slippery

  • Electrical equipment (vibrator) becomes unsafe

• Ensure proper earthing and insulation

8. After Rain Stops

• Check slab surface for:

  • Laitance

  • Segregation

  • Surface damage

• Take corrective measures if needed

One-Line Interview Answer (Perfect)

If rain occurs during slab casting, I stop or control concreting, protect fresh concrete from rainwater, prevent change in water–cement ratio, ensure safety, and if required, form a proper construction joint before resuming work.