Concrete Constipation : When the Pumping System Needs Laxatives

A Little Wisdom Helps You Become Smarter !

Understanding Concrete Pumping Hazards: What Went Wrong !

This video captures a critical construction incident: during concrete pouring, hardened chunks burst upward through the rebar framework. This occurs when a blocked pipeline—often due to oversized aggregates (stones larger than 1/3 of the pipe diameter), improper lubrication, or sudden pauses in pumping—creates dangerous pressure buildup (up to 20+ MPa). The trapped concrete seeks escape through weak spots in the formwork or gaps between rebars.

Workers standing nearby face severe risks:

Impact injuries: Ejected concrete chunks (weighing 5-10 kg) can travel at 5-8 m/s, capable of fracturing bones.

Structural instability: Repeated pressure pulses weaken formwork connections, risking collapse.

Secondary hazards: Vibrations may loosen nearby scaffolding or tools.

Immediate actions:

Evacuate all personnel within a 10-meter radius.

Shut off the pump and SLOWLY release pressure via the relief valve (≥2 minutes).

Use mechanical tools (never hands) to clear blockages after confirming zero pressure.

Prevention steps:

Sieve aggregates onsite—ensure max stone size ≤25 mm for standard 75 mm pipes.

Pump a “lubrication mix” (cement slurry) before concrete.

Maintain continuous pouring—any pause beyond 20 minutes requires pipeline flushing.

Always prioritize safety: 80% of pumping accidents result from ignoring pressure warnings. Stay alert, stay back, and follow protocols.