Using a concrete pump is by far the most efficient way to work with concrete, but that's only as long as it's working as well as it should. Luckily, as long as you follow standard procedures, there's only a minimal risk of any issues arising, but you should know how to deal with them if they do.
One of the more common concrete pump problems is blockages. This can be caused by a number of factors, and it needs to be fixed quickly to continue working safely and effectively.
Is the pipe definitely blocked?
First of all, you'll need to determine whether or not the pipe is actually blocked, or if there's a different problem. If the flow of concrete stops, it's a fairly safe bet that a blockage is the cause, but checking a few other things lets you make certain.
The real telltale sign is pressure. A blockage will cause the pump's pressure to increase, so look for an increase above what you normally find when it's operating. While testing the pump, switch it on for brief periods and watch the pressure gauge closely. If you run it for too long, the build-up of pressure is dangerous.
How to clear a blockage
It might help to narrow down which part of the pipe is the most likely site of the blockage. The simplest way to do this is by gently tapping along the length of the pipe with a hammer, taking care not to damage it and cause further problems.
You'll be able to hear the difference between clear and blocked sections – there should be a distinctive change from hollow to muted sounds.
Once you've determined the location of the blockage, you can get to work clearing it.
Sometimes, you can get the concrete flowing again by simply switching the pumping action between forward and reverse a few times, but if this doesn't work quickly, don't continue.
If this doesn't work, remove the section of pipe where the blockage is, and tap it lightly with a hammer to loosen the obstruction. This should shake it free.
Prevention is better than cure
To avoid a blocked pump in future, follow a few guidelines and minimise the risk.
Always make sure the concrete is mixed properly, not too wet or too dry. Either side of the correct ratio of water to solid material can lead to blockages. Don't leave unused wet concrete sitting around before pumping, as it can begin to dry out.
You should also make sure the pump is fully cleaned and inspected before and after each use, to avoid concrete drying inside the tubes.