scholarly journals Design of portable rheometer with new vane geometry to estimate concrete rheological parameters

2016 ◽  
Vol 23 (3) ◽  
pp. 347-355 ◽  
Author(s):  
Hamza SOUALHI ◽  
El-Hadj KADRI ◽  
Tien-Tung NGO ◽  
Adrien BOUVET ◽  
François CUSSIGH ◽  
...  
Keyword(s):  
Yield Stress ◽  
Coefficient Of Variation ◽  
Test Procedure ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Construction Site ◽  
Wide Range ◽  
Mineral Additions ◽  
High Plastic ◽  
Rheometer Test

This paper presents the development of a portable vane rheometer to estimate concrete plastic viscosity and yield stress. The apparatus can be used not only in laboratory but also on construction site. In this study, new blade geometry was proposed to minimize the effect of segregation of concrete during testing, and also to expand the wide range of concrete work­ability with a slump of approximately from 7 cm to fluid concrete, and concrete with high plastic viscosity such as concrete with mineral additions. The used blade (U shaped and reversed) allows reducing the vibration of the apparatus, and ob­taining more stable measurements. The obtained results permit validating the rheometer test procedure and confirmed that the results are reliable, with a low coefficient of variation of 9% for repetitive test and of 5.8% for reproductive tests.

Influence of Ground Slag on the Rheology of Mortar

2013 ◽  
Vol 438-439 ◽  
pp. 67-71
Author(s):  
Qian Qian Zhang ◽  
Jian Zhong Liu ◽  
Jia Ping Liu
Keyword(s):  
Film Thickness ◽  
Specific Surface ◽  
Yield Stress ◽  
Surface Area ◽  
Specific Surface Area ◽  
Water Film ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Water Film Thickness ◽  
Binder Ratio

The effects of ground slag with different specific surface area on the rheology of mortar at water-binder ratio of 0.25, 0.28 and 0.30 were investigated, and the combined effects of packing density and solid surface area on the rheology of mortar were evaluated in terms of the water film thickness. The results show that with the increasing of specific surface area of slag (220 m2/kg-784 m2/kg), plastic viscosity and yield stress decrease. The correlations of yield stress and plastic viscosity to the water film thickness are basically linear with high correlation R2 values. The action of the ground slag on the rheology of mortar can be characterized by water film thickness, and with the increasing of water film thickness the rheological parameters decrease.

scholarly journals Evolution of flow properties, plastic viscosity, and yield stress of alkali-activated fly ash/slag pastes

2020 ◽  
Vol 5 ◽  
pp. 141-149
Author(s):  
Mohammed Fouad Alnahhal ◽  
Taehwan Kim ◽  
Ailar Hajimohammadi
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Time Intervals ◽  
Increasing Trend ◽  
Binder Ratio ◽  
Drastic Effect ◽  
Effect On Yield ◽  
Alkali Activated

The development of cementless concrete is attracting increasing attention in practice and research to reduce both greenhouse gas emissions and energy consumption of concrete. Alkali-activated materials (AAMs) are one of the viable alternatives to replace Portland cement due to their lower CO2 emissions. This study investigated the evolution of rheological parameters of alkali-activated fly ash/slag pastes as a function of time. Flowability and rheological measurements were carried out to determine the fluidity, plastic viscosity, and yield stress at different time intervals. The effects of the slag content, the concentration of SiO2 in the activator, and the solution/binder ratio were considered. Based on the results, the yield stress and plastic viscosity followed an increasing trend over time coinciding with a reduction in the paste fluidity. The plastic viscosity of AAM pastes was in the range of 1.3–9.5 Pa.s and 2.6–28.9 Pa.s after 5 min and 45 min of mixing, respectively. Given the same alkali activator, the higher content of slag the paste had, the higher yield stress the paste showed. In addition, this paper confirmed that the SiO2/Na2O ratio in the activator had no significant effect on yield stress, but a drastic effect of this ratio was found on the plastic viscosity of the paste.

scholarly journals Rheology, Mechanical Properties and Porosity of Ternary Alkali-Activated Binders Based on Mining Mud Waste with Waste Glass and Metakaolin

CivilEng ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 236-253
Author(s):  
Abdelhakim Benhamouda ◽  
João Castro-Gomes ◽  
Luiz Pereira-de-Oliveira
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Yield Stress ◽  
Relative Yield ◽  
Rheological Behaviour ◽  
Waste Glass ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Alkali Activated Binders ◽  
Alkali Activated

Alkali-activated materials have the potential to replace Portland cement in certain applications. To better understand these binders’ properties, it is relevant to study their rheological behaviour at early ages, like in the case of Portland cement paste. There are already many studies on the rheological behaviour of these materials in the available literature, using fly ash, metakaolin, and ground granulated blast furnace slag as precursors. However, this study discusses the rheological behaviour, mechanical properties, and porosity of ternary alkali-activated binders based on mining mud waste, waste glass, and metakaolin. The precursor consisted of a volume mix of 70% of tungsten mining waste mud, 15% glass waste, and 15% of metakaolin. The activator was a combination of sodium hydroxide and sodium silicate solution. Five activator/precursor (A/P) ratios (0.37, 0.38, 0.39, 0.40, and 0.4) were studied. The result showed that the activator/precursor ratio affects the rheology of paste and their rheological behaviour fit the Bingham model. The relative yield stress (g) and plastic viscosity (h) increased inversely with the A/P ratio, while the workability increased proportionally. Furthermore, some empirical models are proposed to describe the characteristic of yield stress: plastic viscosity and spread diameter versus the A/P ratio and time with a correlation between the rheological parameters and the spread diameter. The increase in A/P ratio has also followed a decrease in compressive strength in all tested samples for all the ages. As expected, an increase of the porosity accompanied the increase of the A/P ratio.

Influences of Fly Ash Level on Cementitious System Performance of Concrete Based on the Quantization Parameter Analysis

2013 ◽  
Vol 405-408 ◽  
pp. 2591-2595
Author(s):  
Liang Shi ◽  
Ye Wu ◽  
Jian Zhong Liu
Keyword(s):  
Fly Ash ◽  
Yield Stress ◽  
Plastic Viscosity ◽  
Parameter Analysis ◽  
Rheological Parameters ◽  
Capillary Absorption ◽  
Class Iii ◽  
Cementitious System ◽  
High Level ◽  
Selection Of

In order to achieve a scientific selection of fly ash used in concrete, the influences of fly ash level on cementitious system rheological parameters, hydration degree and capillary adsorption properties were quantitative analyzed. The results show that Class I fly ash reduces the yield stress and plastic viscosity of cementitious system. The yield stress of system increases dramatically and the plastic viscosity of system reduces when Class III fly ash added. Rheological parameters of cementitious system change little when Class II fly ash added. The higher level fly ash uses the more CSH gel generates and the less Ca(OH)2 crystals generates in cementitious system at early age (3d to 7d). High level fly ash increases the cement paste initial capillary adsorption amount but reduces the capillary absorption rate.

scholarly journals Effect of Silica Fume on the Rheological Properties of Cement Paste with Ultra-Low Water Binder Ratio

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 554
Author(s):  
Juan He ◽  
Congmi Cheng ◽  
Xiaofen Zhu ◽  
Xiaosen Li
Keyword(s):  
Hysteresis Loop ◽  
Rheological Properties ◽  
Yield Stress ◽  
Silica Fume ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Loop Area ◽  
Binder Ratio ◽  
Hysteresis Loop Area ◽  
Water Binder Ratio

The effect of silica fume on the rheological properties of a cement–silica fume–high range water reducer–water mixture with ultra-low water binder ratio (CSHWM) was studied. The results indicate that the W/B ratio and silica fume content have different effects on the rheological parameters, including the yield stress, plastic viscosity, and hysteresis loop area. The shear-thickening influence of CSHWM decreased with the increased silica fume content. When the silica fume content increased from 0% to 35%, the mixture with W/B ratio of 0.19 and 0.23 changed from a dilatant fluid to a Newtonian fluid, and then to a pseudoplastic fluid. When the silica fume content was less than 15%, the yield stress was close to 0. With the increase of silica fume content, the yield stress increased rapidly. The plastic viscosity and hysteresis loop area decreased slightly with the addition of a small amount of silica fume, but increased significantly with the continuous increase of silica fume. Compared with the Bingham and modified Bingham models, the Herschel–Buckley model is more applicable for this CSHWM.

Experimental Research on Rheological Properties of Cemented Mortar in Tail Void Grouting of Shield Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1201-1205 ◽  
Author(s):  
Xiao Hui Yuan ◽  
Yue Wang Han
Keyword(s):  
Rheological Properties ◽  
Flow Pattern ◽  
Yield Stress ◽  
Plastic Viscosity ◽  
Rheological Parameters ◽  
Shear Yield Stress ◽  
Shear Yield ◽  
Binder Ratio ◽  
Water Ratio ◽  
Water Binder Ratio

Grout flow pattern and rheological parameters determine grouting pressure transfer process in annular tail void and filling rate for shield tail void. However, cemented mortar is a mixture of cement, fly ash, sand, bentonite and water, which lead to grout rheological properties and rheological parameters are difficultly determined. Based on orthogonal experimental design method, grout rheological properties were tested by rotational viscometer. Utilizing variance and poly-nonlinear regression analysis, the qualitative and quantitative relationships between mix ratios and rheological parameters were obtained respectively. It is shown that cemented mortar flow pattern commonly agree with Bingham fluid type, and plastic viscosity varies between 1 and 4Pa•s, and shear yield stress varies between 10 to 40Pa respectively. Water-binder ratio and bentonite-water ratio are key influencing factors for grout rheological parameters. With the water-binder ratio increasing and bentonite-water ratio decreasing, plastic viscosity and shear yield stress present reducing tendency.

Laminar-Turbulent Transition Flows of Non-Newtonian Slurries: Models Assessment

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Kofi Freeman K. Adane ◽  
Martin Agelin-Chaab
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Yield Stress ◽  
Stress Ratio ◽  
Rheological Parameters ◽  
Transition Model ◽  
Flow Conditions ◽  
Wide Range ◽  
Engineering Models ◽  
Wall Shear

In this study, a qualitative assessment of transitional velocity engineering models for predicting non-Newtonian slurry flows in a horizontal pipe was performed using data from a wide range of pipe diameters (25–268 mm). In addition, the gamma theta transition model was used to compute selected flow conditions. These models were used to predict transitional velocities in large pipe diameters (up to 420 mm) for slurries. In general, it was observed that most of the current engineering models predict transitional velocities conservatively. Based on the gamma theta transition model results, for large Hedström numbers (He ≳ 105), other methods should be used to predict transitional velocities if a change in the pipe diameter (scale-up) results in an order of magnitude increase in the He value. It was also found that the gamma theta transition model predicted a laminar flow condition in the fully developed region for flow conditions with a small plug region (low-yield stress-to-wall shear stress ratio), which is contrary to what has been observed in some experiments. This is attributed to the local fluid rheological parameters values, which might be different from those reported. However, the gamma theta transition model results are in good agreement with the experimental data for flow conditions that have a large plug region (high-yield stress-to-wall shear stress ratio).

Research of the activity and viability of spermatozoa at different concentrations and proportions of diluents after incubation

2020 ◽  
pp. 88-95
Author(s):  
Svitlana Lobchenko ◽  
Tetiana Husar ◽  
Viktor Lobchenko
Keyword(s):  
Plasma Concentration ◽  
Incubation Time ◽  
Coefficient Of Variation ◽  
Incubation Medium ◽  
Wide Range ◽  
Series Of Experiments ◽  
The Subject ◽  
Boar Spermatozoa ◽  
Native Plasma ◽  
Better Than

The results of studies of the viability of spermatozoa with different incubation time at different concentrations and using different diluents are highlighted in the article. (Un) concentrated spermatozoa were diluented: 1) with their native plasma; 2) medium 199; 3) a mixture of equal volumes of plasma and medium 199. The experiment was designed to generate experimental samples with spermatozoa concentrations prepared according to the method, namely: 0.2; 0.1; 0.05; 0.025 billion / ml. The sperm was evaluated after 2, 4, 6 and 8 hours. The perspective of such a study is significant and makes it possible to research various aspects of the subject in a wide range. In this regard, a series of experiments were conducted in this area. The data obtained are statistically processed and allow us to highlight the results that relate to each stage of the study. In particular, in this article it was found out some regularities between the viability of sperm, the type of diluent and the rate of rarefaction, as evidenced by the data presented in the tables. As a result of sperm incubation, the viability of spermatozoa remains at least the highest trend when sperm are diluted to a concentration of 0.1 billion / ml, regardless of the type of diluent used. To maintain the viability of sperm using this concentration of medium 199 is not better than its native plasma, and its mixture with an equal volume of plasma through any length of time incubation of such sperm. Most often it is at this concentration of sperm that their viability is characterized by the lowest coefficient of variation, regardless of the type of diluent used, which may indicate the greatest stability of the result under these conditions. The viability of spermatozoa with a concentration of 0.1 billion / ml is statistically significantly reduced only after 6 or even 8 hours of incubation. If the sperm are incubated for only 2 hours, regardless of the type of diluent used, the sperm concentrations tested do not affect the viability of the sperm. Key words: boar, spermatozoa, sperm plasma, concentration, incubation, medium 199, activity, viability, rarefaction.

scholarly journals A simulation-based approach to evaluate objective material parameters from concrete rheometer measurements

2019 ◽  
Vol 29 (1) ◽  
pp. 130-140 ◽  
Author(s):  
Florian Gerland ◽  
Alexander Wetzel ◽  
Thomas Schomberg ◽  
Olaf Wünsch ◽  
Bernhard Middendorf
Keyword(s):  
Yield Stress ◽  
High Performance ◽  
Evaluation Method ◽  
High Performance Concrete ◽  
Direct Determination ◽  
Plastic Viscosity ◽  
Flow Properties ◽  
Fresh Sample ◽  
Material Parameters ◽  
Simulation Based

Abstract Modern concretes such as ultra-high performance concrete (UHPC) show excellent strength properties combined with favorable flow properties. However, the flow properties depend strongly on process parameters during production (temperature, humidity etc.), but also change sensitively even with slight variations in the mixture. In order to ensure desired processing of the fluidlike material and consistent process quality, the flow properties of the concrete must be evaluated quantitatively and objectively. The usual evaluation of measurements from concrete rheometers, for example of the ball probe system type, does not allow the direct determination of the objective material parameters yield stress and plastic viscosity of the sample. We developed a simulation-based method for the evaluation of rheometric measurements of fine grained high performance concretes like self-compacting concrete (SCC) and UHPC. The method is based on a dimensional analysis for ball measuring systems. Through numerical parameter studies we were able to describe the identified relationship between measuring quantities and material parameters quantitatively for two devices of this type. The evaluation method is based on the Bingham model. With this method it is possible to measure both the yield stress and the plastic viscosity of the fresh sample simultaneously. Device independence of the evaluation process is proven and an application to fiber-reinforced UHPC is presented.

scholarly journals The influence of sulfate availability on rheology of fresh cement paste

2020 ◽  
Vol 30 (1) ◽  
pp. 54-63
Author(s):  
Willy Mbasha ◽  
Rainer Haldenwang ◽  
Irina Masalova
Keyword(s):  
Yield Stress ◽  
Calcium Sulfate ◽  
Chemical Properties ◽  
Plastic Viscosity ◽  
Cement Clinker ◽  
Flow Properties ◽  
Cement Pastes ◽  
Hardened Properties ◽  
Physical And Chemical ◽  
And Chemical Properties

AbstractNatural gypsum can degenerate into hemihydrate during cement clinker grinding which changes the physical and chemical properties of cement hydration, affecting therefore the fresh and hardened properties of cement based materials. Cement systems containing a constant total amount of calcium sulfate (4%) with relative proportions of hemihydrate and natural gypsum were considered. Rheological measurements were executed on an Anton Paar MCR51 rheometer to evaluate the flow properties of cement pastes. Results show that, the yield stress and the plastic viscosity of cement pastes were affected when the degeneration of natural gypsum exceeded 50%. Above this concentration, the yield stress remarkably increased and a variation in plastic viscosity of about 50% was observed. Using TG-DSC techniques, it was shown that, the amount of formed ettringite could not explain these rheological changes. However, centrifugational packing and SEM-SE measurements confirmed that, more than the amount of ettringite precipitated, ettringite morphology plays a major role in controlling the yield stress and plastic viscosity of fresh cement pastes.

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