A rheometer is a measuring apparatus for determining the flow behavior of materials. Rheometers of the above-mentioned type are known in the configuration of the rotation rheometer and, for example, are described in “Comparison of concrete rheometers: International tests at LCPC (Nantes, France) in October, 2000, NISTIR 6819”. These rheometers have a vessel fillable with high-viscosity material and a measuring device having a rotationally movable measuring geometry for measuring torque. With a rotational movement of the measuring geometry, a torque develops because of the high-viscosity material filled in the vessel, which torque is measured. From this, the flow behavior of the high viscosity material can be determined.
The flow behavior of high-viscosity materials determines their processability, compressibility, and feedability.
In pipelines, for feeding high-viscosity materials such as concrete or sludge, coal slurry, or biological waste, a feeding resistance develops which is dependent upon the flow behavior of the high-viscosity material. A reason for the feed resistance is the friction of the high-viscosity material with the pipeline wall and the deforming work which occurs on the high-viscosity material during transport through a pipeline. The deforming work is caused by the inner deforming resistance of the high-viscosity material.
Due to the feeding resistance, a high-viscosity material pump for feeding the high-viscosity materials over an elevation difference Δh through a pipeline system must generate not only a pressure PΔh which corresponds to the pressure which a high-viscosity material column causes over an elevation difference Δh at the output of the high-viscosity material pump in the connecting region of the pipeline system, but also an additional pressure PFW.
For the pressure PΔh, the following applies as a rule:PΔh=gρΔh,  (1)wherein g is the gravitional acceleration and ρ is the density of the high-viscosity material. The additional pressure PFW must be developed in order to overcome the above-mentioned feeding resistance in the pipeline system.
The consequence is that a high-viscosity material pump must make available at least the feeding pressurePF=PFW+PΔh  (2)in order to feed the high-viscosity material over the elevation difference Δh through the pipeline system.
It is known, for the feeding of pumped concrete through a pipeline system having a given pipeline diameter D and a given pipeline length L, at a desired delivery volume and a specific pumped concrete consistency classified by the slump according to DIN EN 12350-5, to estimate the necessary pressure PFW for overcoming the feeding resistance by means of a nomogram. The slump according to DIN EN 12350-5 is applied as a measure for the flow behavior of concrete. This method of estimating PFW is based on experience values or on a set of measuring data which was recorded for numerous types of pumped concrete of different pipeline systems. One such nomogram is illustrated and shown e.g. on page 53 of the Putzmeister corporate brochure “Betontechnologie für Betonpumpe”.
With a known density pPB of the pumped concrete and a given delivery head Δh of a pipeline system with pipeline length L a conclusion can be drawn as to the feeding pressure PF with this nonogram for a desired delivery volume Q of pumped concrete per time unit.
It is shown, however, that this approach is suitable only for estimating PFW for so-called simple pumped concrete, that is, when the pumped concrete is a ternary mixture comprising admixtures, water and cement as main components. If, for example, simple pumped concrete is mixed with additional substances or admixtures such as plasticizers for specific applications, the flow behavior of concrete is no longer appropriately characterized by the slump according to DIN EN 12350-5. Therefore, for pumped concrete having admixtures, the required feed pressure PF for a pipeline system can no longer be estimated well with the above nomogram.
The known rotation rheometers for high-viscosity materials are not suited either to determine the flow behavior of concrete in such a manner that required feed pressure PF can be ascertained in a reliable manner therefrom.
To determine the feeding pressure PF required in a pipeline system for pumped concrete, to which admixtures are added, or to ascertain a feeding pressure PF for other high-viscosity materials, such as sludge, coal slurry or biological waste, so far difficult pumping attempts have been carried out: The corresponding high-viscosity material is pumped through a test construction having the pipeline system provided for the specific application. On the test construction, the pressure conditions in the pipeline system are then detected for different feeding velocities of the high-viscosity material. In particular in the region connecting the high-viscosity material pump and the pipeline system the pressure occurring is measured. This measured pressure then corresponds to the feeding pressure PF.
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