How and why it is necessary to lubricate the concrete?
In a number of practical applications of suspended particles have to move through a system of pipes. Often, as is the production of cement and concrete, the liquid component of such substances should be minimized; otherwise the quality of the final product is drastically reduced. If you would like to know about mixer details you could choose batch mixer.
But as soon as the liquid level drops, raise the head of other problems. After shifting in a concrete mixer or when pumping mixtures of them starts to thicken. The viscosity of the slurry to flow dramatically increases, and in some circumstances, increasing almost indefinitely, making it a huge amount of time to increase the power consumption for pumping concrete through the pipes, the general consuming excessive load pumps. You could learn more about disperser mixer from here.
Large French cement maker Lafarge to solve this kind of problem addressed to the Swiss Institute of Technology Zurich for help. Using computer modeling of processes such suspensions, and laboratory experiments, Nicolas Fernandez and Roman Mani, seems to be able to move this very important matter in motion.
The key to understanding what is happening has been the recognition that the flow in such dense suspensions in their parameters rather comes down to the interaction between the individual grains of it, rather than to the processes characteristic of liquids. Thus, rheology, deformation and flow of matter in them are closely related to tribological parameters of suspension components – the contact interaction of deformable solids.
At low flow rates, “contacts” between particles suspended occur when wet surfaces facing the liquid film. In this hydrodynamic regime of friction moderately and the pumps are capable of pumping a mixture without much effort. However, with the growth rate of the film is torn between the particles and grains rub against each other as if they were dry. It was at this point after the shift starts thickening.
Even worse is when broken into multiple fragments liquid film disappears completely – that at high solids content in the slurry and a decent frictional happens quite frequently. That’s when the viscosity tends to infinity, and transfer pumps fail.
Once there was understanding of the relationship of shear thickening and suspension friction solid grains together, it became clear how to prevent it. Pilot testing showed: application of suspended cement-based small amount of polymer additives dramatically reduced the coefficient of friction and completely prevented the shear thickening. As the authors note, the opening is able to do away with breakdowns of pumping equipment and at the same time reducing energy costs concrete industry without compromising the quality of products it mixes.