The results of investigations of the rheological properties of typical ceramic slurries used in the investment casting technology – the lost

wax technology are presented in the paper. Flow curves in the wide range of shear velocity were made. Moreover, viscosity of ceramic

slurries depending on shearing stresses was specified. Tests were performed under conditions of three different temperatures 25, 30 and

35oC, which are typical and important in the viewpoint of making ceramic slurries in the investment casting technology.

In the light of the performed investigations can be said that the belonging in group of Newtonian or Non – Newtonian fluid is dependent

on content of solid phase (addition of aluminum oxide) in the whole composition of liquid ceramic slurries.

In this paper, thermal processing of starch slurry in a Couette-Taylor flow (CTF) apparatus was investigated. Gelatinized starch dispersion, after treatment in the CTF apparatus, was characterized using such parameters like starch granule diameters (or average diameter), starch granule swelling degree (quantifying the amount of water absorbed by starch granules) and concentration of dissolved starch. These parameters were affected mostly by the process temperature, although the impact of the axial flow or rotor rotation on them was also observed. Moreover, the analysis of results showed a relatively good correlation between these parameters, as well as, between those parameter and apparent viscosity of gelatinized starch dispersion. Meanwhile, the increase in the value of the apparent viscosity and in shear-tinning behaviour of dispersion was associated with the progress of starch processing in the CTF apparatus. Finally, the CTF apparatuses of different geometries were compared using numerical simulation of the process. The results of the simulation indicated that the apparatus scaling-up without increasing the width of the gap between cylinders results in higher mechanical energy consumption per unit of processed starch slurry.

This paper deals with the effects of modifications to clay-siliceous raw material from Dylągówka (Dynów foothills, SE Poland), which alter the rheological properties of its water suspensions. The investigations were carried out on three samples collected from various depths of the deposit as they considerably differ in their contents of smectite and other minerals. The samples were either modified with soda or activated with sulphuric (VI) acid and used to prepare their water suspensions with various contents of solids. The suspensions were subject to determinations of viscosity and flow curves. Dependencies of three variables of the suspensions (rheological properties, mineral composition of the solid phase, and the modifications introduced) were assessed on the basis of: the contents of the solid phase in the suspensions required to obtain a viscosity of 1000 mPas; hypothetical, calculated thixotropic energy. These show that the amount of solids in the water suspension required to obtain the required viscosity is considerably lower in samples with higher contents of smectite and in those activated with sodium. In turn, the acid activation that partially alters smectite towards a protonated silica gel decreases the viscosity and thixotropy of the suspensions, which was confirmed in the studies of mid-infrared spectroscopy. The conducted studies provide important information needed in designing the mineral composition of drilling fluids and others applications.

The effects of hydroxypropyl methylcellulose (HPMC) on the rheology and viscoelasticity of cement-limestone paste were evaluated, as was the mechanism of HPMC from the viewpoint of zeta potential and adsorption amount. The results revealed that the greater the content of HPMC or the viscosity of its aqueous solution, the lower the fluidity of the composite paste and therefore the higher the rheological parameters. The relation between torque and rotational velocity of cement-limestone paste is linear; nevertheless, the shear thickening degree of paste increased following the addition of HPMC, demonstrating typical viscoelastic properties. The addition of HPMC prolonged the induction duration and delayed the emergence of the exothermic peak of hydration, decreased zeta potential and conductivity, and increased the propensity of suspension particles to agglomerate. The adsorption amount of polycarboxylate superplasticizer (PCE) decreased with increasing aqueous solution viscosity and HPMC concentration due to the winding effect of HPMC’s high molecular chain structure and the competing adsorption of HPMC and PCE.

This study presents general properties of dough as demonstrated within the period of its technological usefulness (i.e, approx. up to 30 min). Eight (8) types of dough made of four (4) types of flour were subjected to experimental tests. During examination of dough, treated as a non-Newtonian fluid, its non-Newtonian (apparent) viscosity was determined as well as its correlations with other rheological quantities. The results of the study were shown in diagrams presenting the course of particular quantities and model correlations of examined types of dough. These relations were used to determine one general expression modeling rheological properties of examined doughs.

Calcium Sulfoaluminate cements (CSA) may be an alternative to Portland cements due to their very high early strength and more environmentally friendly production technology, however they are characterized by a short setting time and high cost. A possible solution to these problems is to mix CSA cement with other binders or additives. In order to test this possibility, CSA cement was mixed with Portland cement and limestone in the amount of 10, 20 and 30 wt. %. A hydration heat test was carried out in the first 72 hours after the components were mixed, measured were compressive and flexural strength after 1, 2, 7 and 28 days, and rheological properties, including early shrinkage. A negative interaction between CSA and CEM I 42.5R was observed, leading to deterioration of mechanical properties of the mortars. The study did not indicate a similar negative interaction between CSA cement and limestone.