Abstract
Abstract Pumping is an easy and flexible process to place concrete inside a formwork. Many studies have recently been performed to understand and optimize the pumping process and identify the main differences between pumping of conventional vibrated concrete and self-consolidating concrete (SCC). However, due to pumping, changes in fresh concrete properties and the air-void system have been noticed. This paper describes the consequences of pumping on the fresh properties of SCC by means of two experimental pumping campaigns. In many cases, the concrete undergoes a large shear rate in the pipe, thus (re-)dispersing cement particles. This is expected to be the main cause of the observed decrease in plastic viscosity, V-Funnel flow time and pumping pressure resulting from increased flow rate or pumping time. The changes in yield stress or slump flow are anticipated to be influenced by the same phenomenon, but the final outcome is assumed to depend on the availability of residual superplasticizer in the mixing water. Pumping can cause a stable SCC to become segregating if both the yield stress and plastic viscosity decrease, or it can provoke a significant loss in filling ability, passing ability and self-consolidation of the concrete if the yield stress increases dramatically.
Highlights
Pumping of concrete is the fastest and most efficient way to place concrete inside a formwork
Previous pumping experiments on self-consolidating concrete (SCC), have led to the conclusion that the pressure loss (Dp)—flow rate (Q) relationship is in agreement with thelinearity in the rheological behavior of the concrete: i.e., if the flow is Bingham, the Dp - Q relationship is straight, and if the SCC shows shear-thickening behavior, the pumping curve is non-linear [20]
2.2.2 Testing procedure at the Universitede Sherbrooke. This testing procedure aimed at studying the influence of rheology and mix design on pumping pressure [8, 14]
Summary
Pumping of concrete is the fastest and most efficient way to place concrete inside a formwork. Scientific studies have contributed to understanding the flow process of concrete inside a pipe These studies included the evaluation of tribology [4,5,6,7,8,9,10] as well as the assessment of the thickness of the lubrication layer [11,12,13]. Different models are available to predict pumping pressure, based on the applied flow rate, length and radius of the pipeline, the rheological properties of the concrete, and the properties of the lubrication layer. Previous pumping experiments on SCC, have led to the conclusion that the pressure loss (Dp)—flow rate (Q) relationship is in agreement with the (non)linearity in the rheological behavior of the concrete: i.e., if the flow is Bingham, the Dp - Q relationship is straight, and if the SCC shows shear-thickening behavior, the pumping curve is non-linear [20]. Materials and Structures (2016) 49:4657–4677 increased pumping time or flow rate are described and analyzed
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