What are the inner dimensions of a standard 35-litre gauge box (farma) for measuring aggregates by volume?
Correct Answer: C. L=27 cm, B=27 cm, H=48 cm
📚 Detailed Explanation: 35-Litre Gauge Box Dimensions
Why C (27 cm × 27 cm × 48 cm) is correct: A gauge box (farma or measure box) is a rectangular open-top container used to measure aggregate volumes in volume batching. The standard 35-litre farma is sized to hold the loose volume equivalent of one 50 kg bag of cement, making it convenient to maintain the mix proportions batch-by-batch.
Volume Verification
Inner dimensions: L = 27 cm, B = 27 cm, H = 48 cm
Volume = L × B × H
= 27 × 27 × 48 cm³
= 34,992 cm³
= 34.992 litres ≈ 35 litres
Why 35 Litres?
| Bag Size | Cement Mass | Loose Volume (approx.) | Gauge Box Size |
|---|---|---|---|
| Standard OPC bag | 50 kg | ~33–35 litres | 35-litre farma |
One farma of aggregate corresponds to one farma of cement (for 1:1 mix) or multiple farmas for richer mixes. For a 1:2:4 mix: 1 farma cement : 2 farmas sand : 4 farmas coarse aggregate per batch.
Checking the Other Options
Option A: 30 × 25 × 30 = 22,500 cm³ = 22.5 L (too small)
Option B: 39 × 25 × 32 = 31,200 cm³ = 31.2 L (not 35 L)
Option C: 27 × 27 × 48 = 34,992 cm³ ≈ 35 L (correct)
Option D: 220 × 25 × 40 = 220,000 cm³ = 220 L (far too large)
Option B: 39 × 25 × 32 = 31,200 cm³ = 31.2 L (not 35 L)
Option C: 27 × 27 × 48 = 34,992 cm³ ≈ 35 L (correct)
Option D: 220 × 25 × 40 = 220,000 cm³ = 220 L (far too large)
- Standard 35-litre gauge box: 27 cm × 27 cm × 48 cm.
- Sized to match the loose volume of one 50 kg bag of cement.
- Volume batching is only permitted for concrete of grade M15 and below per IS 456.