Transportation of Concrete – Methods, Requirements and IS Code

After mixing, concrete must be transported from the mixing point to the placement location as quickly and carefully as possible. Transportation of concrete is a critical stage where workability can be lost, and segregation or contamination can occur if not managed properly. This guide covers all methods, time limits, and quality requirements for RTMNU Concrete Technology students.

1. Objectives of Concrete Transportation

The transportation of concrete must achieve the following objectives:

• Deliver concrete to the point of placement without loss of homogeneity
• Maintain workability within acceptable limits
• Avoid segregation and bleeding during movement
• Prevent contamination from external materials
• Complete within the specified time limit before initial set begins
• Minimise slump loss during transit

2. Essential Requirements for Concrete Transportation

As per IS 456:2000 Clause 13, the following requirements must be met:

• Concrete must be placed in its final position within 90 minutes of water addition (or before initial setting, whichever is earlier)
• No water shall be added to concrete after mixing to restore workability that has been lost during transit
• Containers and equipment used must be clean, non-absorbent, and free from contamination
• Segregation must be prevented at all stages of transport
• For transit mixer delivery: maximum 300 drum revolutions after water addition (IS 4926)

3. Methods of Transportation of Concrete

A. Manual Methods

1. Headload / Manual Carrying

• Concrete placed in pans/baskets and carried on head or by hand
• Suitable only for very short distances (<15 m) and small quantities
• Slow, labour-intensive, risk of segregation with every step
• Only for minor works; not recommended for structural concrete

2. Wheelbarrows

• Single-wheel barrows for short distances on relatively smooth surfaces
• Distance: up to 50–60 m on level ground
• Prone to segregation over rough terrain; use pneumatic tyres over planks
• Suitable for small residential and minor works

B. Mechanical/Equipment Methods

3. Mortar Pans / Barrows (Power-assisted)

• Motor-driven or powered barrows for medium distances on relatively level ground
• Faster than manual wheelbarrows; still limited to ground-level access

4. Dumpers / Tippers (Dumper trucks)

• Small self-propelled dumpers (0.5–3 m³) used for medium distances on site
• Suitable for flat or gently sloping sites
• Risk of segregation over rough ground – concrete should be workable but not too wet
• Not suitable for distances >500 m on site or for highly workable mixes

5. Transit Mixer (Truck Mixer)

• Rotating drum on truck; maintains concrete uniformity during long-distance transport
• Capacity: 4–10 m³ per load
• Drum rotates at mixing speed (8–12 rpm) for mixing; agitating speed (2–4 rpm) during transport
• Maximum transit: 90 minutes from water addition or 300 drum revolutions (IS 4926)
• Used exclusively for Ready Mix Concrete (RMC)
• Can transport concrete up to 50–150 km depending on traffic and temperature

6. Belt Conveyors

• Rubber conveyor belts carry concrete continuously from mixing point
• Suitable for long horizontal distances (up to 1–2 km) and gentle inclines
• Advantages: continuous delivery, high output (up to 100 m³/hour)
• Limitations: risk of drying and segregation at transfer points; end of belt must have a scraper to prevent mortar loss; not suitable for very steep slopes
• Used in dam construction and large infrastructure projects

7. Concrete Pumps

• Pump forces concrete through a rigid or flexible pipeline to the placement point
• Most versatile method – can reach heights of 100+ m and distances of 500+ m
• Types: Truck-mounted boom pump, static/trailer pump, separate placing boom
• Requires pumpable concrete (slump 100–175 mm, well-graded, no gap-graded aggregate)
• Used extensively in high-rise buildings, bridges, tunnels

8. Cranes and Skips (Hoppers)

• Crane lifts a skip (large hopper/bucket) filled with concrete to the placement point
• Capacity per skip: 0.5–3 m³
• Used for tall structures (high-rise columns, bridge piers, dams) where pumping is not feasible
• Slower than pumping but suitable for all mix types including stiff mixes
• Risk: concrete must not be dropped more than 1.5 m to prevent segregation

9. Chutes (Inclined Slides)

• Inclined smooth channels (steel or timber-lined) that carry concrete by gravity
• Slope: 1:2 to 1:3 (vertical:horizontal) – if too flat, concrete stalls; if too steep, segregation occurs
• Used for downward placement from a higher level (e.g., from transit mixer to foundation)
• End of chute must have a baffled deflector to prevent segregation
• Not suitable for horizontal transport

10. Tremie Pipe

• Vertical steel pipe used for placing concrete underwater or in deep water/bored piles
• Pipe kept immersed in freshly placed concrete (minimum 600 mm) to prevent water entry
• Concrete is fed from the top and displaces previously placed concrete upward
• Used for underwater foundations, caissons, drilled shafts

Summary Table of Transportation Methods

4. Concrete Pumping – Detailed

Concrete pumping is the most commonly used method for high-rise buildings and large infrastructure today. Here is what makes it work:

Requirements for Pumpable Concrete

• Slump: 100–175 mm (medium-high workability)
• Well-graded aggregates (no gap grading – prevents arching in pipe)
• Maximum aggregate size: ≤ 1/3 of pipe internal diameter (typical pipe: 100–125 mm → max agg. 40 mm)
• Adequate fines content (cement + FA particles <300 μm ≥ 400 kg/m³)
• Use of superplasticizer to achieve workability at low W/C ratio

Pumping Procedure

1. Prime the pump and pipeline with cement slurry (1 bag cement + water) to lubricate the pipe
2. Start pumping at low pressure; gradually increase
3. Maintain continuous pumping – stopping causes blockage
4. At end of pour, flush pipeline with water then clean with foam ball (“pig”)

Common Pump Blockages – Causes

• Too stiff concrete (low slump)
• Gap-graded aggregate forming arches
• Long stoppage allowing concrete to stiffen
• Insufficient fines content in mix

5. Time Limits for Transportation (IS 456:2000)

Critical note: After the time limit, concrete must NOT be used. Adding water to restore lost workability is strictly prohibited per IS 456 Clause 13.

6. Preventing Segregation During Transport

• Use properly designed, cohesive mix with adequate fines
• Do not drop concrete from more than 1.5 m height (IS 456)
• Use baffles at end of chutes and at discharge points
• Avoid very wet mixes (>175 mm slump) in wheelbarrows or dumpers
• Keep transit time to minimum – reduce distance from batching to placement
• Use air-entraining agent or VMA for long haul in harsh conditions
• Avoid vibrating or jolting loaded barrows over rough surfaces

7. SVG Diagram – Methods of Transporting Concrete

Dumper/Tipper Distance: <500 m Site roads

Transit Mixer 50–150 km 90 min limit (IS 4926) RMC delivery

Belt Conveyor Up to 2 km Dams / Large works

Concrete Pump Height: 100+ m Distance: 500+ m High-rise / tunnels

Crane + Skip Any height Tall structures Max drop: 1.5 m

Chute Downward only Slope: 1:2 to 1:3 Foundations

Tremie Pipe Underwater Deep piles Subaqueous

⏱ IS 456:2000 Clause 13 – Maximum Time Limit Concrete must be placed within 90 minutes of water addition. No water to be added to restore workability.

📌 Pump needs slump 100–175 mm | Max drop from height: 1.5 m | Transit mixer: 90 min or 300 revolutions

8. Exam Tips (RTMNU)

• ✅ IS 456:2000 Clause 13 = Transportation requirements; IS 4926 = Ready Mix Concrete – cite both.
• ✅ Maximum time: 90 minutes from water addition to final placement – most frequently asked.
• ✅ Maximum height of free drop: 1.5 m (IS 456) – preventing segregation.
• ✅ Chute slope: 1:2 to 1:3 (V:H) – if slope too gentle, concrete stalls; too steep, segregation.
• ✅ Pumpable concrete slump: 100–175 mm with well-graded aggregate and superplasticizer.
• ✅ Transit mixer: mixing speed = 8–12 rpm; agitation speed = 2–4 rpm.
• ✅ “Why should we not add water to concrete during transport?” – Increases W/C ratio, reduces strength, violates IS 456.

9. Key Takeaways

• Concrete must reach its final position without losing uniformity, workability, or experiencing contamination.
• Maximum time from water addition to placement: 90 minutes (IS 456:2000 Clause 13).
• Adding water to restore lost workability during transport is strictly prohibited.
• Free drop height: maximum 1.5 m to prevent segregation.
• Concrete pumping is the preferred method for high-rise buildings – requires slump 100–175 mm.
• Transit mixers carry RMC – maximum 90 minutes or 300 drum revolutions (IS 4926).
• Chute slope should be between 1:2 and 1:3 for effective and segregation-free flow.

10. FAQs

Q1. What is the maximum time allowed between mixing and placing concrete?

As per IS 456:2000 Clause 13, concrete must be placed in its final position within 90 minutes of the addition of water to the dry mix, or before the onset of initial setting – whichever is earlier. In hot weather (>30°C), this limit reduces to 45–60 minutes.

Q2. Why should water not be added during concrete transport to restore workability?

Adding water increases the water-cement ratio beyond the design value, directly reducing compressive strength (Abrams’ Law). Even a small addition of 5 litres/m³ can reduce 28-day strength by 2–4 MPa. IS 456:2000 strictly prohibits this practice.

Q3. What type of concrete is used with pumping?

Pumpable concrete requires a slump of 100–175 mm, well-graded aggregates (no gap grading), maximum aggregate size ≤ 1/3 of pipe diameter, adequate fines content, and typically a superplasticizer to achieve workability at low W/C ratio. Gap-graded aggregate causes blockages.

Q4. What is the slope requirement for concrete chutes?

Concrete chutes should have a slope between 1:2 and 1:3 (vertical:horizontal). If slope is gentler than 1:3, concrete stalls and stops flowing. If steeper than 1:2, concrete flows too fast causing segregation – coarse aggregate separates from mortar.

Q5. What is a tremie pipe and when is it used?

A tremie pipe is a vertical steel pipe used to place concrete underwater or in deep bore piles where direct placement is impossible. The pipe is kept continuously immersed at least 600 mm in the fresh concrete to prevent water entry. Concrete is continuously fed from the top, displacing previously placed concrete upward without mixing with water.

🔗 Related Reading: Placing of Concrete – Methods and Requirements

🔗 Related Reading: Mixing of Concrete – Methods and Types of Mixers

📖 Reference: IS 456:2000 Clause 13 and IS 4926 – Ready Mixed Concrete