Concrete in large quantities can be pumped across long distances for placing in inaccessible sites. This system comprises a hopper that receives concrete from a mixer, a pump to propel the concrete, and pipelines that facilitate its delivery.
For direct-acting pumps, the concrete enters the pump via the inlet valve under the action of gravity and suction created by the movement of the piston. This concrete is then forced into the pipeline and out through the outlet valve by the forward movement of the piston. These pumps can deliver concrete up to a horizontal distance of 1500 feet and a vertical distance of 140 feet. On the other hand, squeeze pumps utilize rotating blades to move concrete from the hopper into a flexible pipe. The concrete is then advanced to the delivery pipe by the squeezing action of revolving rollers. Commonly installed on trucks, squeeze pumps are capable of deploying concrete through an extendable boom to distances in the range of 300 feet horizontally and 100 feet vertically. The diameter of the pipes, crucial for smooth transport, is selected to be three times larger than the maximum aggregate size in the concrete. Furthermore, the consistency of the concrete mix determines the efficiency of pumping. Overly dry mixes can lead to high resistance within the pipes, while overly wet mixes are prone to segregation.
Concrete can be transported through pipelines over long distances to be placed in locations difficult to access, such as deep foundation pits.
The system includes a hopper for receiving concrete, a pump, and pipelines to deliver the concrete.
In a direct-acting pump, the movement of the piston aids the entry of concrete into the pump through the inlet valve. Subsequently, as the piston moves forward, the concrete is pushed into the pipeline and comes out through the outlet valve.
Alternatively, a truck-mounted squeeze pump uses rotating blades to feed the concrete from the collecting hopper into a flexible pipe. Revolving rollers squeeze the concrete forward to the delivery pipe, and it may be delivered using a folding boom.
The pipe diameter should be thrice the maximum size of aggregates in the concrete.
Lastly, a concrete mix with a slump between one and a half and four inches is ideal for pumping. Pumping mixes that are too dry cause high frictional resistance in the pipes, while excessively wet mixes might result in segregation.
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