Concrete Blow Back and Pump Back Policy

In accordance with the Concrete NZ recommendation, Allied Concrete will not accept concrete ‘pumped back’ or ‘blown back’ into trucks by any concrete pump. This is due to the high risk of injury and explosive force due to air pressure.

Pumping back may only occur following a full risk mitigation proposal submitted to & authorised by Alllied Concrete. This includes controls that extend far beyond the standard pump back practice.

Hazard Identified

This Concrete NZ Readymix Sector Group Safety Alert addresses the issue of concrete blow-back and pump-back into the concrete truck mixing bowl, which can be an inherently dangerous procedure
unless carefully controlled.

Blow-back uses high air pressure to move residual concrete from the line or boom pump back into the truck mixer or bowl. Air pressure will cause anything inside the pipe to act as a high velocity projectile.

Pump-back is the return of residual concrete back into the truck mixer or bowl by either line or boom pumps. Excessive pumping pressure creates similar problems to blow-back.

RISK 1 High air pressure or pump line pressure, along with pipe
movement during blow-back or pump-back, can cause pipe joints to fail and break apart.

RISK 2 Concrete in the pipe is subjected to high pressure during
blow-back or pump-back and can cause the hose to eject from the concrete bowl or material to rebound and exit the concrete bowl. In both situations there is the potential to cause injury to bystanders, or equipment and/or property damage.

RISK 3 Climbing a concrete truck ladder carrying a line pump pipe or trying to manoeuvre a line pump pipe while not having three points of contact creates a high risk of fall from height.

RISK 4 Control measures previously deemed as acceptable in both blow-back or pump-back have not been adhered to resulting in injury or damage.