Diphasic investigation of the visco-elastoplastic characteristics of highly flowable fine mortars

The rheological properties of the lubrication layer between the bulk concrete and the wall of the pumping pipe is a key factor governing the pumpability of concrete. In this study, the rheological behavior of the lubrication layer was simulated as a suspension of different volumetric contents of fine sand (<1.25 mm) in visco-elastoplastic cement pastes, namely fine mortars. Various fine mortar and their corresponding cement paste mixtures were proportioned with water-to-binder ratios of 0.36-0.70, binder content of 472-853 kg/m(3), and volumetric content of fine sand of 0.31-0.48. The visco-elastoplastic properties of the fine mortar and their cement paste mixtures were evaluated using parallel-plate and coaxial cylinders measuring systems, respectively. According to the experimental results, all the investigated cement paste and fine mortar mixtures exhibited shear-thinning behavior. Moreover, good empirical relationships were established between the visco-elastoplastic properties and mini-slump flow values of the investigated mixtures. The established correlations can simplify the rheological evaluation of the lubrication layer materials. The obtained results revealed that increasing the fine sand content increased the relative visco-elastoplastic properties of the investigated mixtures. New diphasic models were proposed and successfully employed to evaluate the coupled effect of the relative solid packing fraction of fine sand, dispersion of binder particles, excess paste volume, and cement paste characteristics on workability, rheological properties, and compressive strength of the fine mortar. These proposed models were in better agreement with the experimental values compared to the existing models in literature. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The rheological properties of the lubrication layer between concrete and pumping pipe wall were investigated through experiments and simulations, showing that increasing fine sand content enhances the visco-elastoplastic properties of the mixtures. Empirical relationships between rheological properties and mini-slump flow values were established, and new models for evaluating lubrication layer materials were proposed.