Concrete Pumping is a typical technique used in construction wherein ready-mix concrete runs through a pipeline to be placed in hard-to-access locations or locations that's impossible to get into at all. Not only does it allow contractors to save time in hauling concrete, but it also keeps them from additional labor costs, especially for high-rise structures.
Since concrete runs through a pipe during pumping, one of the most common issues is pipeline blockage. When this happens, it costs the contractor time, effort, and labor costs just by sorting it out. Here are a few causes of pump blockages and how to never deal with them in your project:
Issues with the Concrete Mix Design
One of the biggest causes of blockage is using an incorrect ratio of your concrete mix's materials. Not all concrete mixes are for concrete pumping use. If the concrete mix is too fluid, chances are bleeding may occur, which means that water would separate from the mix, which is typically caused by using gap-graded aggregates. In most cases, excessive bleeding ultimately leads to segregation wherein the aggregates on your mix separates from the cement paste. If segregation or bleeding occurs, your mix might become too dense, causing chunks of cement or aggregates to be stuck somewhere in the pipeline. If this happens, your concrete mix might not be able to go smoothly to its intended endpoint. However, it is not precisely the operator's job to monitor the mixing of the concrete since it is being procured as a ready-mix most of the time. It is still essential to ensure that the concrete mix delivered to the site has the correct proportions to prevent delays and equipment damage.
Inadequate Pipe Connection Planning
When it comes to setting pipes, it’s best to remember that fewer pipes laid out and fewer elbows installed means fewer potential blockages. Setting up the pumping system, plan the shortest distance possible from the pump's outlet to the target area, and if possible, use little to no elbow pipes. In the case of 90-degree elbow pipes, the ideal radius is more extensive than 500mm. When the target area involves a higher level, the horizontal pipeline has a shut-off valve and is less than 15% the length of the vertical pipeline. Also, it's imperative to check the hoses' coupling because, most of the time, mismatched hoses cause concrete to flow slower than when the diameters of the hoses match.
Delayed Pumping
When concrete sits for too long, especially under intense temperatures, there is a tendency for the concrete mix to be too stiff. When exposed to sunlight, just like humans, concrete tends to get dehydrated, making the slump too small. This is not a scenario that can be fixed by just adding water. It is never okay to add water to ready-mix concrete because it will ruin the mixture’s proportion. In a situation wherein the mix is too stiff, the machines might not be able to push it out of the pipes, or it may be able to do so, but you would be pushing the machine to its limit by using high pumping pressures that may cause blockage or damage to the equipment. That is why it is vital to set strict schedules for concrete pumping because the concrete mix just couldn't wait. Every second that it remains under the sun, it's a second closer to wasting a whole concrete batch.
Issues with the Pumping Equipment Used
Before renting or procuring pumping equipment for a project, the pipes' specifications and the machine itself should be taken into consideration, primarily since not all machines and pipes work for all types of projects. Projects also differ in size, length, and height, requiring specific pipe lengths and detailed motor specifications to pump the required volume of concrete for the area. Also, proper maintenance of equipment is necessary to avoid blockages. It's a testament to the saying that "prevention is key to success." Poorly managed equipment may not be an issue at the moment, but it will be over time. For example, the pipes are not cleaned after use. Once the concrete stuck inside the pipes dries up, and the pipes are used again, blockages will likely occur from the dirty pipes' concrete build-up.
Human Error
It doesn't matter if you use the most expensive or most advanced equipment if the operator and the crew are not trained for the job. The human factor in concrete pumping is just as important as all the potential causes mentioned in this article. A skilled pump operator should be knowledgeable on how to operate the pumping machine that is being used and the procedures on how to set up the pumping system correctly. The operator's job is to regularly monitor all parts of the system to pinpoint which pipe could potentially encounter blockages. Of course, the crew has an essential role in the pumping process as well. They have to coordinate with the operator on how to layout out the pipes properly because failure to do so may cause misalignments in the setup, or pipes might be inclined incorrectly, which may prevent the concrete from flowing properly cause damage to the pipe itself.
Tips In Clearing Concrete Pump Blockage
Before attempting to clear out a blockage manually, the operator may try to reverse the pump and restarting it a few times to see if the pump could clear the blockage by itself. The operator should only attempt this a few times since it may create too much pressure in the blocked area, which may cause the pipes to explode.
Once the block is located, release any sort of pressure in the hose before clearing it. If there's high pressure inside the pump, there's a chance that the pipe might burst. This is also why it is never advisable to stand over a pipe whenever someone is clearing out a blockage.
Do not use compressed air when removing a blockage. It does not work and could potentially be dangerous. The only time that compressed air could be used is when clearing out residue in the pipes which do not have blockages.
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