Rheological Properties of Alkali-Activated Brick Powder Based Pastes: Effect of Alkali Activator and Silicate Modulus

2018 ◽  
Vol 276 ◽  
pp. 185-191
Author(s):  
Martin Vyšvařil ◽  
Pavla Rovnaníková ◽  
Martin Keppert
Keyword(s):  
Yield Stress ◽  
Rheological Behaviour ◽  
Gel Formation ◽  
Material Behaviour ◽  
Flow Properties ◽  
Rheological Characterization ◽  
Polymerization Kinetic ◽  
Brick Powder ◽  
Viscous Modulus ◽  
Alkali Activated

The rheological behaviour of alkali-activated materials prepared by activation of a brick powder by alkaline solution (alkali + water glass) is described. The influence of the composition of activation solution (NaOH vs. KOH, varied silicate modulus) on the flow properties (yield stress, consistency coefficient, fluidity index) and the evolution of the elastic modulus (G ́) and the viscous modulus (G ́ ́) over time were studied. The rheological characterization was completed by frequency sweep tests with the aim of investigating the material behaviour more in detail. The results show that the pastes are thixotropic suspensions with very low yield stress. The potassium activator decreases the yield stress and viscosity of the pastes and retards the polymerization kinetic. The brick pastes become more rigid and more viscous with increasing silicate modulus. This also leads to an acceleration of gel formation in brick pastes.

Physicochemical and Electro-Rheological Characterization of Kaolinite / CMS / Silicone Oil Fluid

2010 ◽  
Vol 446 ◽  
pp. 33-41
Author(s):  
Thomas Reiss ◽  
Saoussen Laribi ◽  
Jean-Marie Fleureau ◽  
Jean Francois Tassin
Keyword(s):  
Electric Field ◽  
Yield Stress ◽  
Applied Electric Field ◽  
Silicone Oil ◽  
Rheological Behaviour ◽  
Rheological Characterization ◽  
Clay Particles ◽  
Observed Behaviour ◽  
Composite Nature

The aim of this study is to elaborate electro-rheological fluids based on kaolinite. the scientific characterization made it possible the identification of the composite nature and the checking of the intercalation of the polymer among the clay particles The rheological behaviour of the fluid depends on the electric field. A yield stress of the suspensions is observed, which increases with the applied electric field. An interpretation based on the different modes of association between the clay particles is proposed to account qualitatively for the observed behaviour.

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.

scholarly journals The Effect of the Activator/Precursor Ratio on the Rheological Properties of the Alkali-activated Mining Waste Mud Paste

2020 ◽  
Author(s):  
Abdelhakim Benhamouda ◽  
João Castro-Gomes ◽  
Luiz Pereira-de-Oliveira
Keyword(s):  
Compressive Strength ◽  
Sodium Hydroxide ◽  
Rheological Properties ◽  
Yield Stress ◽  
Rheological Behaviour ◽  
Mining Waste ◽  
Bingham Model ◽  
Precursor Ratio ◽  
Alkali Activated ◽  
The Ideal

To determine the properties of paste, mortar or concrete, it is necessary to understand its rheological behaviour first. This study discusses the effect of the activator/precursor ratio on the rheological properties of the alkali-activated paste. The pastes consisted of a mix of 70 % of tungsten mining waste mud, 15% waste glass and 15% of metakaolin. This mix was activated by combining sodium hydroxide and sodium silicate. Five activator/precursor (a/p) ratios were studied: 0.37, 0.38, 0.39, 0.40 and 0.41. The result obtained shows that the rheology of the pastes is affected by the activator/precursor ratio. The rheological behaviour of the paste fits the Bingham model. The yield stress (τ0) and plastic viscosity (μ) increase inversely with the activator/precursor ratio (e.g. a/p=0.37 gives τ0=84.19 and μ=0.4185; a/p=0.41 gives τ0=30.389 and μ=0.2937). The workability increases proportionally with the activator/precursor ratio (e.g. a/p=0.37 gives a slump=133 mm; a/p=0.41 gives a slump=158 mm). The compressive strength decreases when the activator/precursor ratio increases (e.g. at 28 days for a/p=0.37, the compressive strength was 19.6 MPa; for a/p=0.41, the compressive strength was 13 MPa). Finally, the ideal ratios were 0.38 and 0.39.

scholarly journals Alkali-activated laterite binders: Influence of silica modulus on setting time, Rheological behaviour and strength development

2021 ◽  
pp. 100175
Author(s):  
Cyriaque Rodrigue Kaze ◽  
Adeyemi Adesina ◽  
Gisèle Laure Lecomte-Nana ◽  
Thamer Alomayri ◽  
Elie Kamseu ◽  
...  
Keyword(s):  
Setting Time ◽  
Rheological Behaviour ◽  
Strength Development ◽  
Alkali Activated

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.

scholarly journals Yield Stress Model for Natural Debris Flows in Presence of Fine and Coarse–Grained Sediments

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1865
Author(s):  
Leonardo Schippa
Keyword(s):  
Yield Stress ◽  
Debris Flows ◽  
Rheological Behaviour ◽  
Coarse Fraction ◽  
Coarse Grained ◽  
Stress Model ◽  
Coarse Sediment ◽  
Fine Grain ◽  
Sediment Fraction ◽  
Coarse To Fine

When dealing with natural geo–hazards, it is important to understand the influence of sediment sorting on debris flows. The presence of coarse fraction is one of the aspects which affects the rheological behaviour of natural viscous granular fluid mixtures. In this paper, experiments on reconstituted debris flow mixtures with different coarse–to–fine sediment ratios are considered. Such mixtures behave just as non–Newtonian yield stress fluids and their rheological behaviour is largely affected by the presence of coarse fraction. Experimental results demonstrate that yield stress is very sensitive not only to bulk sediment concentration but also to coarse sediment fraction. A novel yield stress model is presented. It accounts for an empirical grading function depending on the coarse–to–fine grain content. The yield stress model performed satisfactorily in comparison with the experiments, showing that it is almost independent of the coarse–to–fine grain fraction in case of dominant coarse sediment content.

The Identification of Cracks Formed during the Spontaneous Drying and Hardening of Alkali-Activated Slag for Different Curing Times

2016 ◽  
Vol 827 ◽  
pp. 340-343
Author(s):  
Libor Topolář ◽  
Hana Šimonová ◽  
Lubos Pazdera
Keyword(s):  
Brittle Materials ◽  
Material Behaviour ◽  
Alkali Activated Slag ◽  
Hardening Process ◽  
Curing Method ◽  
Activated Slag ◽  
Alkali Activated

This paper reports the results of measurements during hardening and drying of specimens made of alkali activated slag mortars. The aim of this paper is introduce the effect of curing method and time on the microstructure of alkali activated slag mortars. An understanding of microstructure−performance relationships is the key to true understanding of material behaviour. The results obtained in the laboratory are useful to understand the various stages of micro-cracking activity during the hardening process in quasi-brittle materials such as alkali activated slag mortars and extend them for field applications.

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