Experimental Observation on Variation of Rheological Properties during Concrete Pumping

Workability of concrete varies during pumping. Even though concrete satisfies the required workability before pumping, it often does not satisfy the required standard after pumping. Moreover, serious problem could happen such as segregation and blockage. In this study, the rheological properties of concrete change during pumping from the pressure distribution over the pipe length was investigated. The rheological properties and the pressures measured from seven different real-scale pumping tests with 116m to 1000m long pipelines and 24MPa to 100MPa concrete were analyzed. As a result, it was found that the rheological properties vary gradually along the pipeline, and could abruptly change inside the pump. The variation of rheological properties during pumping seems to be attributed in part to the increase of water absorption in aggregates under high pressure and the additional mixing effect, namely, intensive shearing under high pressure inside pump.