Nowadays, Pumpable concrete is one of the main types of concrete used for massive buildings for the ease of construction. Pumped concrete has many advantages over conventional concrete.
Pumpable concrete is the concrete which can easily pass through a pipeline without causing segregation and bleeding is called pumped concrete.
They are mostly used in concrete pumps for high rise building. Using pumpable concrete you can transfer concrete from mixing place to construction place without causing any delay in concrete placing. If you use any other types of transporting concrete there will be a delay in each step while placing the concrete.
In order to avoid these delay and less labor work, pumped concrete is a very good recommended method. The pump should be made in such a way that the friction at the inner wall should less.
There should be sufficient water content available in the concrete for achieving good flow of concrete through the pipeline. But if the water content is too high, the water is forced to move faster than the aggregates in concrete. This leads to the expulsion of water from concrete faster and creates clogging of aggregates of concrete.
What are the requirements of pumped concrete?
- The slump value recommended for good pumpable concrete ranges from 50mm to 150mm.
- The water-cement ratio should not be too high. If the water content is too high, then the water alone will move faster along the pipe results in blocking of aggregates of concrete in the pipe.
- The concrete should not be too wet or too dry.
- The pumped concrete should not be sticky.
- Air entrainment admixture is also helpful for the transmission of concrete.
What are the types of concrete pumps used for concrete pumping?
There are two types of pumps used for pumping of concrete. they are direct acting pump and squeeze pump. They are shown in the below figure.
1.Direct acting pumps
Generally, direct acting pumps are the commonly used types of pumps for pumping of concrete. They have a horizontal piston as shown in the below figure.
The concrete is fed into the hopper of the direct acting pump. The working of this type of pump is purely by reciprocal motion of the piston. From this motion, a suction pressure is created inside the pump.
The working of the direct acting pump is such a way that, during the suction stroke the inlet valve opens while the outlet valve remains closed. During this process, the concrete will enter into the suction pipe from the hopper.
After the suction stroke, the inlet valves close and outlet valve open like in the above figure. During this process, the piston will push the concrete toward the pipe and this process continues.
The maximum size of aggregate used in the concrete for direct acting pump should less than 1/3 rd of the diameter of the pipe to avoid clogging. The motion of concrete always in the form of impulse. However, the output of the pipe should maintain a constant flow.
2.Squeeze concrete pumps
The second type of pump is squeezed concrete pumps. The squeeze concrete pumps convey concrete by squeezing its pumping tube installed in the cylindrical drum as shown in the below figure.
Why blockage occurs in pumpable concrete?
The blockage is a common problem that comes if you didn’t take care of the instructions properly. The first cause of blockage in pumps is due to the action of friction due to the aggregates and ingredients in the concrete on the pipe wall is very high.
The second problem is water is being forced out of the mix causes accumulation of large particles inside the pipe. When choosing a right pump, you should take care of its length, the number of bents, the diameter of the pipeline, length of flexible hose etc..
Hope you could understand this pumped concrete topic well.If you have any doubt regarding this topic. Please comment below.