8.4 : 泵送混凝土

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.