Visco-plastic properties regulation of 3D-printable cement mixtures

Abstract

The results of experimental studies of the rheological behavior of 3D printing multicomponent cement mixtures containing a filler, a viscosity modifier and the fiber reinforcing are presented. Squeezing tests were used to study the rheological behavior. To assess the plasticity index, which characterizes the ability of mixtures to maintain aggregative stability during extrusion, the squeezing test with a constant strain rate was used. To assess the shape stability, the squeezing test with a constant loading rate was used, according to the results of which the values of structural and plastic strength, plastic deformations of multicomponent cement systems were found, characterizing their ability to retain their shape under the action of increasing compressive stresses during printing. Quantitative data have been obtained on the effect of types of fillers and viscosity modifiers of various chemical and mineralogical composition and fineness on the plasticity and form stability of cement mixtures. It has been established that the most effective viscosity modifiers are metakaolin and complex modifier tetrapotassium pyrophosphate in combination with gum. The regulation of viscoplastic properties and aggregative stability of cement systems during their introduction is determined by the change in the properties of the dispersed phase and the dispersion medium in the heterogeneous system "cement - water". Rational dosages of the filler, viscosity modifiers are determined, at which the criteria values for 3D printing processes are provided for the values of plasticity, structural strength and deformability under load.