Sammendrag
A pipe viscometer system equipped with differential pressure sensors and a Coriolis flow meter was integrated into a small-scale batch mixer to develop a novel concept for continuous slurry characterization. Previous studies have shown that cement slurries can exhibit particle migration away from pipe walls, which will impact the measured friction pressure loss and equivalently the wall shear stress particularly in small-diameter pipes. The focus of this research is to probe the possible impact of particle migration within the current setup, comparing measurements with those acquired using a scientific rheometer. The research approach involves comparing flow curves derived from pipe viscometer readings with offline measurements conducted using a rheometer equipped with a concentric cylinder geometry using a rotor with either smooth or grooved surface. To facilitate this comparison, differential pressure and flow rate data were converted into shear stress and shear rate values, following the Mooney-Rabinowitsch relationship. Experiments were performed using a simulated fresh cement paste suspension prepared by mixing an aqueous xanthan gum solution with silica powder. Steady-state viscosity measurements from both the pipe viscometer and rheometer produced consistent results, emphasizing the similarity in the shape and slope of the flow curves. Notably, rheometer measurements acquired using the smooth cylinder geometry closely resembled the measurements from the pipe viscometer for all solutions and suspensions tested, and also aligned well with the conventional viscometers employed in field applications. For pure xanthan gum solutions, we observed a close agreement between the geometries considered in the rheometer measurements and the pipe viscometer. On the other hand, the analysis revealed particle migration effects when comparing smooth and grooved cylinder geometries and testing dispersed silica suspensions. These discrepancies were more pronounced with increasing silica particle content and, therefore, should be duly considered when employing the proposed pipe viscometer system for the continuous characterization of fresh cement paste. The novelty of this approach lies in the comprehensive evaluation of the pipe viscometer setup, examining factors that could potentially influence viscosity measurements. This investigation aims to ensure precise control when implementing the system into a full-scale batch mixer for automated fluid characterization or continuous ("on-the-fly") mixing of cement paste.
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