Showing papers on "Rheometer published in 2022"

3D printable concrete with natural and recycled coarse aggregates: Rheological, mechanical and shrinkage behaviour

Abstract: In the current study, we examine the effect of using natural and recycled coarse aggregates in designing 3D printable concrete. We assessed the rheological behaviourusing a dynamic shear rheometer, and it was observed that the addition of coarse aggregates significantly decreased the yield stress and marginally lowered the plastic viscosity. This was attributed to the increase in the paste and water film thickness with the addition of larger aggregates. Therefore, a reduction in the superplasticizer dosage is required to obtain coarse aggregate mixtures with similar yield stress and buildability to the control mixture. The mechanical properties were evaluated by using beam and cube samples cut out from printed wall elements. A marginal decrease in compression and flexural strength was observed for both the mixtures with natural and recycled coarse aggregates. The total and autogenous shrinkage assessment was performed using mould cast prismatic specimens, while the shrinkage cracking potential was evaluated using the restrained ring test. The coarse aggregate mixtures showed lower total and autogenous shrinkage. Notably, the addition of the saturated recycled aggregates significantly lowered the autogenous shrinkage, possibly due to internal curing. As a result, a relatively lower strain rate factor and slower development of tensile stresses occurred in the restrained shrinkage test, increasing the cracking age for the coarse aggregate mixtures. The current study, therefore, shows good potential for using natural and recycled coarse aggregates in 3D printable concrete.

3D printable concrete with natural and recycled coarse aggregates: Rheological, mechanical and shrinkage behaviour

Abstract: In the current study, we examine the effect of using natural and recycled coarse aggregates in designing 3D printable concrete. We assessed the rheological behaviourusing a dynamic shear rheometer , and it was observed that the addition of coarse aggregates significantly decreased the yield stress and marginally lowered the plastic viscosity . This was attributed to the increase in the paste and water film thickness with the addition of larger aggregates. Therefore, a reduction in the superplasticizer dosage is required to obtain coarse aggregate mixtures with similar yield stress and buildability to the control mixture. The mechanical properties were evaluated by using beam and cube samples cut out from printed wall elements. A marginal decrease in compression and flexural strength was observed for both the mixtures with natural and recycled coarse aggregates. The total and autogenous shrinkage assessment was performed using mould cast prismatic specimens, while the shrinkage cracking potential was evaluated using the restrained ring test. The coarse aggregate mixtures showed lower total and autogenous shrinkage. Notably, the addition of the saturated recycled aggregates significantly lowered the autogenous shrinkage, possibly due to internal curing. As a result, a relatively lower strain rate factor and slower development of tensile stresses occurred in the restrained shrinkage test, increasing the cracking age for the coarse aggregate mixtures. The current study, therefore, shows good potential for using natural and recycled coarse aggregates in 3D printable concrete.

Rheological Behaviour of WMA-Modified Asphalt Binders with Crumb Rubber

Abstract: Crumb rubber (CR) is one of the materials most widely used in the road infrastructure industry due to its mechanical and environmental benefits as an asphalt binder modifier. Nonetheless, CR decreases the workability of mixes by increasing the viscosity of the binder, leading to an increase in the production temperatures of asphalt mixes. However, warm mix technologies can reduce the temperature demand associated with these processes. The preceding explains the growing interest in producing rubberised asphalt binders incorporating warm mix asphalt (WMA) additives. In this research, the mechanical and rheological properties of a 60/70 penetration grade asphalt binder modified with CR (at a dosage of 15, 18 and 21% by the wet process) and WMA chemical additives (Evotherm M1 and Iterlow T) were investigated. Laboratory tests included penetration, softening point, rotational viscosity, frequency sweep through dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. The results indicate that CR increases the stiffness of the asphalt binder, which is reflected in a lower penetration grade and improved softening point. It also improves its rutting resistance but decreases fatigue performance. Furthermore, it has been shown that under the conditions studied, the higher the CR content, the more elevated the degree of stiffness and performance of the asphalt binder. On the other hand, WMA technology decreases asphalt stiffness and performance at high temperatures.

A Comprehensive Review on MEMS-based Viscometers

Abstract: Viscosity is an important rheological parameter, which needs to be measured accurately in various industrial applications to improve the quality of the product. Micro-electro-mechanical system (MEMS)-based microfluidic viscometers are nowadays overpowering conventional types of viscometers due to many advantages such as compatibility for both Newtonian and non-Newtonian fluids, small size, higher shear rates, no solvent evaporation, small sample size requirement (in micro and nano-litres), and better accuracy. This paper summarizes a comprehensive review on the state-of-the-art of MEMS-based technologies combined with microfluidics for realizing the viscometers to determine various fluidic parameters, important for applications in different fields like biopharmaceuticals and protein therapeutics, lubricants/adhesives, healthcare, food industries, cosmetics, concrete, paints, fuel and petroleum industries, etc. This review covers the basic sensing principles of various types of MEMS-based technologies useful for viscometer applications, such as pressure, diaphragm, viscometer/rheometer on a chip (VROC), acoustic, cantilever etc. Limitations of different types of commonly available tabletop viscometers are outlined. Considering the present and future applications of MEMS-based viscometers, their role in industrial applications are also discussed in detail.

A Review of Microfluidic Devices for Rheological Characterisation

Abstract: The rheological characterisation of liquids finds application in several fields ranging from industrial production to the medical practice. Conventional rheometers are the gold standard for the rheological characterisation; however, they are affected by several limitations, including high costs, large volumes required and difficult integration to other systems. By contrast, microfluidic devices emerged as inexpensive platforms, requiring a little sample to operate and fashioning a very easy integration into other systems. Such advantages have prompted the development of microfluidic devices to measure rheological properties such as viscosity and longest relaxation time, using a finger-prick of volumes. This review highlights some of the microfluidic platforms introduced so far, describing their advantages and limitations, while also offering some prospective for future works.

Digital rheometer twins: Learning the hidden rheology of complex fluids through rheology-informed graph neural networks

Abstract: Significance Science-based data-driven methods that can describe the rheological behavior of complex fluids can be transformative across many disciplines. Digital rheometer twins, which are developed here, can significantly reduce the cost, time, and energy required to characterize complex fluids and predict their future behavior. This is made possible by combining two different methods of informing neural networks with the rheological underpinnings of a system, resulting in quantitative recovery of a gel’s response to different flow protocols. The platform developed here is general enough that it can be extended to areas well beyond complex fluids modeling.

Tensorial formulations for improved thixotropic viscoelastic modeling of human blood

Abstract: Recent work modeling the rheological behavior of human blood indicates that blood has all the hallmark features of a complex material, including shear-thinning, viscoelastic behavior, yield stress, and thixotropy. There is renewed interest in the modeling of human blood with thixo-elasto-visco-plastic rheological models. Previous work [Armstrong and Tussing, Phys. Fluids 32, 094111 (2020)] has led to the development of the enhanced thixotropic viscoelastic model for blood (ethixo-mHAWB; called here, after a minor modification, ETV) that incorporates viscoelasticity to a thixotropic model for the stress contributed by the rouleaux aggregates, in addition to describing using a nonlinear viscoelastic model the stress contributed by the individual red blood cells deforming under the action of the flow. This model has shown superior performance in fitting human blood steady state and transient rheological data from a strain-controlled rheometer [Horner et al., J. Rheol. 62, 577–591 (2018); 63, 799–813 (2019)] as compared to other alternate models. In the present work, we first develop another variant of the ETV model, the enhanced structural stress thixotropic-viscoelastic (ESSTV) model, and the modification patterned following an elastoviscoplastic model developed recently [Varchanis et al., J. Rheol. 63, 609–639 (2019)]. We develop full tensorial stress formulations of the rouleaux stresses for both the above-mentioned models, resulting in the t-ETV and t-ESSTV models. We use steady state and step-ups, and step-downs in shear rate data to independently fit the parameters of all before-mentioned models. We compare predictions against experimental data obtained on small, large, and unidirectional large amplitude oscillatory shear conditions. We find that the full tensor stress formulations t-ETV and t-ESSTV significantly improved the predictive capability of the earlier ETV model.

Rheological characterization of complex fluids through a table-top 3D printer

Abstract: Abstract 3D printing is changing the way we conceive, design, and build 3D objects in mechanical, biomedical, aerospace, construction, automotive and maritime industries. In the current work, the nonlinear rheological behaviour of polymer melts is measured through a table-top 3D printer (3D RheoPrinter) that, smartly modified, allows inline investigation of viscosity, extrudate swell and melt fracture. By using a piezoresistive mini-transducer, the innovative system is designed to be applicable to all Fused Deposition Modelling (FDM) 3D printers by a simple and cost-effective modification of a state-of-art nozzle. The measurements of the nonlinear rheological behaviour are compared with traditional, rotational rheology. Two biodegradable polymers, i.e. polylactic acid and polycaprolactone, are investigated as model systems to test the 3D RheoPrinter. The results of the shear viscosity and the first normal stress difference coefficient, as function of shear rate, show a good agreement between the 3D RheoPrinter and rotational rheometer with an error of about 6 % for a confidence interval of 96 % . Moreover, the 3D RheoPrinter can still be used as 3D printer. In the last part of this work, it is presented a printing test for building 3D structures in which the results show controllable resolution by means of the measured rheological information such as the extrudate swell. The vision of this work is that an inline rheological characterization, possible with the developed 3D RheoPrinter, can enable automatic process optimization and quality assurance to the 3D printing community. The social and scientific impacts of this work are maximized by the cost-efficiency and simplicity of the design that makes it within reach of the general public. The 3D RheoPrinter opens for a rheological experimentation to a broad audience and it offers important insights to bring FDM to the next level of resolution.

Effect of tannic acid modified bamboo fiber on the performance of soybean bio‐asphalt/styrene‐butadiene‐styrene modified asphalt

Abstract: This study resolves the poor enhancement problem of high-temperature performance and lower dissolution of styrene-butadiene-styrene (SBS) modified asphalt and soybean bio-asphalt (SBA) (extracted from waste soybean oil) by tannic acid (TA) modified bamboo fiber (MBF). The rheological properties and microscopic morphologies of the modified asphalt and fibers were investigated by dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR) tests, and Fourier transform infrared (FTIR) spectroscopy. The results showed that the rutting factor and deformation recovery rate of 3% MBF/3% SBS/SBA modified asphalt at 64°C increased by 78.4% and 31.99% as compared with those of 5% SBS modified asphalt. Further, the phenolic hydroxyl group of TA reacted with C═O groups in SBA to form a strong connection between BF and bio-asphalt. Fluorescence microscopy analysis revealed that SBS solubilization and BF formed a uniform and stable network structure in the modified asphalt. This study provides a useful, greener, and cost-effective strategy for the effective utilization of industrial waste (BF and waste soybean oil) by converting into advanced functional materials for highway and construction industries novel and hence can concomitantly decrease environmental pollution and enhance energy conservations.