How do concrete rheology, tribology, flow rate and pipe radius influence pumping pressure?
Finding the critical factors that influence the pressure during pumping of concrete has been investigated for years. From fluid mechanics, the relationship between pressure and flow rate, radius or viscosity is known. In the practical guidelines for pumping of conventional vibrated concrete (CVC) the viscosity term is replaced by the concrete yield stress. However, recently, the influence of viscosity on pumping pressure has been reevaluated for self-consolidating concrete (SCC).
In this paper, the influence of concrete rheology, tribology, flow rate and pipe radius on pumping pressure are discussed, based on full-scale pumping tests. The concrete mixtures varied from pumpable CVC to segregating SCC. The influence of flow rate and viscosity on pumping of concrete has been confirmed. It is also shown that with a 20% decrease in pipe radius (from 125 to 100 mm), the pumping pressure can be roughly doubled. An increase in yield stress also increases the pumping pressure, but its influence is only visible when the viscosity is approximately constant. The total flow resistance in the tribometer also appears to correlate well with the pumping pressure, proving that the developed tribometer mimics quite well the flow of concrete in a pipe.