Friction and Shear: As concrete is pumped through the delivery system, it encounters friction and shear forces. These forces can cause a reduction in slump by altering the flow properties of the concrete. In other words, the concrete may become less workable due to the energy expended in moving it through the pump's pipes and hoses.
Pressure: The pressure applied during pumping can compact the concrete and reduce its slump. This effect is more pronounced with high-pressure pumping systems.
Mix Design: The mix design of the concrete should take into account the anticipated effects of pumping on the slump. Some concrete mixes are specifically designed for pumping and may include adjustments to maintain the desired workability after pumping.
Pump Configuration: The type of concrete pump and its configuration can impact the extent of slump loss. For example, line pumps, which are often used for lower-pressure applications, may cause less slump loss compared to high-pressure boom pumps.
To address the issue of slump loss during pumping, concrete mix designs can be adjusted to compensate for the anticipated loss in workability. This may involve using a mix with a slightly higher initial slump so that, after pumping, the concrete reaches the desired consistency at the placement location. Experienced pump operators can also make adjustments to the pump's settings to minimize slump loss.
It's important to note that while some slump loss is expected during pumping, it should be within acceptable limits as specified by the project's requirements and industry standards. Proper communication between the concrete supplier, pump operator, and construction team is crucial to ensure that the concrete arrives at the placement location with the desired workability for the intended application.
