Papers by Keyword: Rheology

Abstract: The bulk density of the injection grout is an important factor, as its additional weight could cause damage to hardened decorative plasters. This can be particularly noticeable on larger surfaces. This study used five types of lightweight filler as a density-reducing component in hydrated lime-based grouts. The commonly used limestone filler was completely replaced by an expanded or granulated filler with a loose bulk density of up to 900 kg m⁻³; the rheological properties of the prepared grouts were then studied using a hybrid rheometer. The lime grouts were non-Newtonian, shear-thickening fluids exhibiting rheopectic behaviour (i.e. they stiffened over time). The type of filler dramatically affected the flowability of the grouts. The yield stress and plastic viscosity of the grouts decreased when lightweight fillers were used. As the filler density decreased, the grouts became expectantly less stiff. However, they showed a higher proportion of elastic behaviour than viscous behaviour, indicating that they have a strong microstructure that is resistant to external influences. There was no increase in loss factor values at higher frequencies, indicating that there was no separation of the liquid from the grout structure. From a rheological point of view, expanded glass appeared to be the most effective of the lightweight fillers used.

Abstract: Ice slurry offers a promising solution for enhancing energy efficiency and environmental sustainability in industrial refrigeration and thermal energy storage applications. This review critically examines the effects of additives and production methods on the thermo-physical properties of ice slurry, focusing on viscosity and heat transfer performance. Additives such as ethylene glycol (6.5–10.3%), sodium chloride (up to 9%), and propylene glycol (5–24%) significantly enhance heat transfer coefficients by up to 33%, while alumina-based nanofluids (0.2 wt%) increase thermal conductivity by as much as 67%. Optimal ice packing factors (10–25%) and advanced production techniques, including direct contact and fluidized bed methods, improve energy efficiency, scalability, and operational reliability while mitigating issues such as particle agglomeration and viscosity rise. The study emphasizes rigorous methodological transparency with explicit equation definitions, controlled variables, and standardized measurement units (e.g., W/m²K for heat transfer, kg/m·s for viscosity). These findings provide valuable insights to guide the development of robust, high-performance ice slurry systems for large-scale cooling and energy storage applications.

Abstract: This study investigates the rheological and optical properties of sustainable palm oil-based offset printing inks, comparing four formulations with varying pigment concentrations (Palm Ink-15, Palm Ink-16, Palm Ink-17, and Palm Ink-18) against a conventional ink sample. Through rheology testing, we analyzed viscosity, yield value, and shortness to understand ink flow characteristics. Optical density measurements and colorimetric assessments in CIE L*a*b* coordinates were conducted to evaluate ink performance across different film thicknesses. The results indicate that palm-based inks exhibit a superior balance between viscosity and yield value, allowing for effective ink transfer and enhanced color saturation. Palm Ink-17, in particular, demonstrated the most rapid color intensity buildup with increased thickness, making it optimal for applications requiring rich, saturated blue tones. These findings suggest that palm oil-based inks are not only environmentally friendly but also exhibit performance characteristics suitable for high-quality offset printing applications.

Abstract: Long chain polymers are reported to be effective in reducing drag in turbulent flow systems. However, most of the effective polymers are synthetic, which are costly, non-biodegradable, and toxic that raises environmental concerns. Natural polymers, as eco-friendly alternatives, are gaining interest as drag-reducing additives (DRA), but single natural polymers have lower drag reduction (DR) efficacy compared to synthetic ones and degrade under high shear stress. This study aims to investigate biopolymer complexes from hibiscus leaves (HL) and okra (OK) as eco-friendly DRAs, comparing their performance with individual components. Biopolymers were extracted from dried hibiscus leaves and okra and diluted to concentrations of 200–1000 ppm. Complexes were formulated by mixing 200–1000 ppm HL extract with 1000 ppm OK extract. The extracts were characterized using Fourier Transform Infrared Spectroscopy (FTIR), meanwhile all the drag reducing solutions were assessed for viscosity, viscoelasticity and DR performance using an oscillating rheometer under different shear rate (0 – 200 s^-1) and frequencies (0 – 100 Hz). All the polymer solutions showed non-Newtonian shear-thinning behavior. The biopolymers and their complexes also exhibited significant viscoelastic properties which is important for DRA stability in turbulent flow. OK solutions achieved up to 79% DR at 1000 ppm, while HL solutions reached an average of 99% DR at concentrations of 400 ppm and above. However, HL-OK complexes had lower DR efficacy, with a maximum DR of 72% at 800 ppm HL – 1000 ppm OK. This might be due to the high concentration altering the water's properties and increasing viscosity, which increases drag.In conclusion, HL and OK complexes have potential for drag reduction, but future research should optimize concentration ratios, test over a broader range of shear rates, and explore other natural polymers complexes to achieve the synergistic effect.

Abstract: Volcanism is a fundamental planetary process, and understanding the dynamics of lava flows is critical for both hazard mitigation and geological studies. The final length and morphology of a lava flow are governed by a complex interplay between effusion rate, total volume, topography, and the lava's evolving thermo-rheological properties. While empirical power laws relating flow length to effusion rate or volume have proven useful, they do not fully capture the physical processes driving flow behavior, particularly the effects of crust formation and fragmentation. This paper presents an integrated theoretical framework that links macroscopic flow dynamics with the microscale processes of fragmentation. We begin by deriving scaling laws for flow length and width based on a Herschel-Bulkley fluid model. We then introduce a novel component to this framework by postulating that key rheological parameters evolve as a function of the flow's developing prefractal dimension, which quantifies its fragmentation and complexity. Finally, we propose a modified power law for the final flow length that accounts for energy dissipation due to both viscous shearing and the creation of new prefractal surfaces. By analyzing observational data from various basaltic to rhyolitic lava flows, we calibrate and discuss the model's empirical coefficients. The results demonstrate that highly fragmented lava flows like 'a'ā have their runout distance significantly reduced by the energetic cost of their increasing complexity, consistent with field observations. This framework provides a more physically robust foundation for forecasting lava flow behavior and interpreting their final morphologies.

Abstract: This study evaluates the impact of replacing natural sand (NS) with quarry waste sand (QWS) or recycled concrete sand (RCS) at varying substitution rates (0%, 25%, 50%, 75%, and 100%). The analyzed properties include Abrams cone slump, superplasticizer demand (SP), rheological and tribological parameters, mechanical strength, capillary water absorption, and shrinkage. The results show that QWS-based concrete exhibits better workability and requires less superplasticizer, whereas RCS-based concrete necessitates a higher admixture dosage. Both QWS sand and RCS sand significantly enhance the rheological and tribological properties of concrete Moreover, QWS sand provides higher mechanical strength than NS sand, with a strength gain of up to 16% at full replacement (100% QWS sand) at 90 days. Conversely, RCS sand reduces compressive strength by 28.6% at 28 days. and negatively affects porosity and capillary water absorption. However, these negative effects are mitigated when the RCS sand replacement is limited to 25%. QWS sand-based concrete exhibits slower shrinkage and reduced deformability compared to NS sand-based concrete. Predictive strength models were established based on experimental parameters, displaying a high correlation coefficient and a low root mean square error. Replacing NS sand with QWS sand or RCS sand reduced production costs, lowered carbon emissions, minimized waste, and preserved natural resources, offering a sustainable approach for concrete applications.

Abstract: The influence of polyamide-6 (PA6), polyamide-12 (PA12), and their compositions was analyzed to determine the rheological behavior of the feedstock with 43% solid loading. The feedstock with Cu/PA composite constituents were extruded into filaments. The sphericity of particles, particle distribution, and voids was identified using Scanning Electron Microscopy (SEM). The capillary rheometer method was utilized to examine how shear rate and temperature impact the results. The viscosity and shear rate of the material was assessed at different temperatures and shear rates using an L/D ratio of 20 mm and a diameter of 11 mm capillary rheometer. The test results indicated that the polyamide composition influenced the feedstock's rheological properties. The viscosity of the feedstock decreased with an increase in the polyamide composition. Feedstock Cu/PA6 with a composition of 14wt%-Cu has the higher rheological properties among the variation of other composition both for PA-6 and PA-12. Viscosity and Flow energy activation Cu/PA-12 higher than Cu/PA-6.

Abstract: The study investigates the impact of quaternary ammonium and pyridinium salts on the rheological properties of metakaolin-based geopolymer pastes, with a focus on their application in 3D printing technology The experimental results demonstrated that the addition of these salts increased both the plastic viscosity and yield stress of the geopolymer mixtures, with the effect intensifying with higher concentrations and longer aliphatic chains. The coefficient of consistency derived from Herschel-Bulkley model increased from 1.78 up to 3.83 Pa·sⁿ and the yield stress rose from 3.4 up to 31.8 Pa. The study also observed a shift from shear-thickening to shear-thinning behaviour and reduction in thixotropic properties with increased dosages of the admixtures, which is beneficial for 3D printing. The mechanical properties of modified geopolymer mortars were also tested and the results revealed quite negligible effect of admixtures on flexural strength. The compressive strength was slightly reduced by up to 12%. The findings suggest that these admixtures are effective in modifying the rheological properties of geopolymers, making them more suitable for advanced applications like 3D printing.

Abstract: Warm-Mix Asphalt (WMA) additives are used to improve the performance and workability of the asphalt binders. This study used a nano-based saline, Zycotherm, to reduce the viscosity and improve the high-temperature performance of the asphalt binders. To investigate the impact of Zycotherm, penetration, softening point, viscosity and Dynamic Shear Rheometer (DSR) rutting parameter tests were carried out. Based on the results, the Zycotherm-modified asphalt binder with a percentage of 3% lowered the penetration by around 40% and the softening point by 4%, while increased the viscosity by 10% when compared to the control asphalt binder. Rheological testing showed a decrease in the complex shear modulus value and a decrease in the phase angle by around 24% for the Zycotherm modified asphalt binder, which means that the rutting resistance decreases by 13%. Zycotherm modified asphalt binder with a percentage of 1.5% showed nearly similar results as the 3% in terms of lowering the penetration by 20% and softening point by 2% while increased the viscosity even more than the 3% Zycotherm by an overall percentage increase of 11% when compared to the control asphalt binder. For the Rheological testing, the Zycotherm modified asphalt binder with a percentage of 1.5% also showed a 12% decrease in phase angle and complex shear modulus values.

Abstract: The melt flow behavior of polylactic acid (PLA) composites reinforced with iron fillers at different extrusion temperatures was significantly explored to improve their hot melt extrudability and printability in FFF 3D printing technology. PLA/Fe composites have been developed to produce 3D polymer composite (PMCs) filaments for high-strength and magnetic filament applications. The melt flow properties, including melt flow rate (MFR) and flow behavior index (n), of PLA/Fe composite filaments were measured at 200 °C, 220 °C, and 240 °C. Furthermore, the velocity measurement on the composite filament melt was conducted during the melt flow test. A simulation model of the capillary tube in melt flow indexer was developed to predict the melt flow behavior and properties of the polymer composite using Computational Fluid Dynamics (CFD) simulation. The extrusion velocity of the model was compared with the experimental results. The cell Reynolds numbers of the PMCs melt were determined at the testing temperatures. The extrusion velocity and cell Reynolds numbers of the PMCs tended to increase with increasing testing temperatures, while the average velocity decreased four times with doubling the extruder diameter.