Influence of water/cement ratio, and type and concentration of chemical additives on the static and dynamic yield stresses of Portland cement paste

The influence of water/cement (w/c) ratio, and type and concentration of two chemical additives, lignosulfonate and polycarboxylate, on the static (SYS) and dynamic (DYS) yield stresses of Portland cement paste was studied. Large differences between both magnitudes express the existence of, at least, two different microstructural levels. This information is relevant for the design in concrete applications. Specifically, it was found that larger differences between the microstructures that characterize both yield stress values were obtained when (w/c) ratio decreased and the amount of the plasticizers increased. With the empirical functions that were proposed for these dependencies, the calculation of the hydraulic power of a positive displacement pump was made. Results indicate that higher pumping power is required for cement pastes with lower w/c ratios and low polycarboxylic additive content, and when lower w/c ratio is combined with high amount of lignosulfonate additive. (C) 2019 Elsevier Ltd. All rights reserved.