Which of the following statements about pumped concrete (pumpcrete) is/are true? (a) Pipe diameter ≤30 cm (b) Slump: 5–8 cm (c) w/c ratio: 0.5–0.65
Correct Answer: D. All of these
📚 Detailed Explanation: All Three Statements About Pumped Concrete Are Correct
Why D (All of these) is correct: All three statements describe standard specifications for pumped concrete (pumpcrete). Each is grounded in practical engineering requirements for the concrete to be pumpable (fluid enough to move through the pipe without blockage) while being cohesive enough to resist segregation.
Analysis of Each Statement for Pumped Concrete
| Statement | Specification | Reason / Standard | Correct? |
|---|---|---|---|
| A. Pipe diameter ≤30 cm | Typical pipeline diameter: 100–200 mm (≈10–20 cm); max ≤300 mm (30 cm) for standard pumping operations | Larger pipes require larger pumps; 300 mm is the practical upper limit for standard construction pumps; aggregate size must be ≤1/3 of pipe diameter | ✓ TRUE |
| B. Slump: 5 cm to 8 cm (50–80 mm) | Slump 50–100 mm (medium workability); some standards quote 50–80 mm minimum | Too low a slump (<50 mm): mix too stiff; high friction; pipe blockage. Too high (>150 mm): segregation; paste separates. Medium slump 50–100 mm is optimal for pumpability | ✓ TRUE (within accepted range) |
| C. w/c ratio: 0.5 to 0.65 | w/c typically 0.45–0.65 for pumped concrete | Lower w/c: stiff mix; pipe blockage. Higher w/c: segregation during pumping; bleeding. Range 0.5–0.65 provides adequate fluidity with cohesion | ✓ TRUE |
Full Specification for Pumped Concrete (Pumpcrete)
| Parameter | Specification |
|---|---|
| Pipeline diameter | 100–200 mm (not exceeding 300 mm) |
| Slump | 50–100 mm (medium workability) |
| w/c ratio | 0.45–0.65 |
| Maximum aggregate size | ≤1/3 of pipe diameter (e.g., ≤33 mm for 100 mm pipe) |
| Cement content | Minimum 300 kg/m³ for pumpability; sufficient paste to coat aggregates and lubricate pipe |
| Pumping pressure | Up to 10–15 MPa; modern truck pumps reach 60–100 m vertical height |
| Admixtures | Plasticisers/superplasticisers to improve flowability without increasing w/c |
- All three statements are correct: pipe ≤30 cm; slump 5–8 cm; w/c 0.5–0.65.
- Pumped concrete (pumpcrete) requires a carefully balanced mix: fluid enough to pump, cohesive enough not to segregate.
- Aggregate size must be ≤1/3 of pipe diameter to prevent bridging and blockage.