Experimental study on the influence of two different additives onto the flow behaviour of a fresh cement paste

The effects of the concentration of two different additives, lignosulfonate and polycarboxilate, in the rheological parameters of fresh cement pastes were investigated. The geometry of concentric cylinders with a narrow gap was used together with a viscometer. The experimental data shown in the rheograms were fitted with the Herschel–Bulkley model. As expected, the higher the concentration of the additive, the lower the yield stress and consistency of the material. However, a different trend was observed in the flow index with both additives. This behaviour was explained on the basis of the different nature of the interaction between the particles due to the adsorption of each type of additive. As an example, the influence of additives on the velocity profile shown by the cement paste in a pipeline was determined. A limiting radius was obtained, depending on the value of yield stress.