Isolating the effects of thixotropy in geopolymer pastes

Brandvold, Allison S.; Al-Chaar, Ghassan; Kriven, Waltraud M.

doi:10.1111/jace.18996

Cited by 8 publications

(7 citation statements)

References 39 publications

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“…Two types of waterglass (WG) containing sodium and potassium GP formulations were prepared with different water molarity (11 and 13 M) in order to assess how the amount of water affected the extent of efflorescence. To prepare sodium WG (Na-WG), a sodium metasilicate solution methodology outlined by a recent research group 36,37 was employed. To formulate the solution, the necessary amount of deionized (DI) water was determined, based on either 11 or 13 M in WG, and poured into a polypropylene beaker.…”

Section: Methodsmentioning

confidence: 99%

Investigation of geopolymer efflorescence durability problems: Causes and possible solutions

Mokhtari,

Ozer,

de Sá Ribeiro

et al. 2024

J Am Ceram Soc.

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Experimental investigations were conducted to assess the impact of factors such as relative humidity (RH%) and the H2O molarity of waterglass on the efflorescence behavior of geopolymer composites. Samples with sodium (Na) and potassium (K) bases were prepared, having varying waterglass molarities (M) (at 11 and 13 moles of water). These samples were categorized into three groups exposed to different average RH ranges: (i) 0%–70% RH, (ii) 70%–90% RH, and (iii) 90%–100% RH. This study analyzed the occurrence of efflorescence and its stability, employing analytical techniques such as x‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy to examine the formation and characteristics of efflorescent deposits. Additionally, mechanical testing was conducted to evaluate the compressive and flexural strengths of the geopolymer samples, considering the impact of efflorescence on their durability. For instance, in the composite geopolymer specimen containing 11 M water, at a RH of 80%, the compressive strength is decreased by approximately 25% from 56.4 to 42.3 MPa. The findings revealed that when the RH falls within the 70%–90% range, a decrease in water molar content from 13 M to 11 M leads to a more pronounced occurrence of efflorescence when compared to other conditions. Efflorescence may also occur in different RH ranges and water molarities, but its occurrence is significantly lower compared to the 70%–90% RH and 11 M water.

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Section: Methodsmentioning

confidence: 99%

Investigation of geopolymer efflorescence durability problems: Causes and possible solutions

Mokhtari,

Ozer,

de Sá Ribeiro

et al. 2024

J Am Ceram Soc.

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“…For a Newtonian fluid, the rheological curve of shear stress against shear rate is a straight line starting from the origin. The swelling fluid also has a rheological curve: the fluid flows when an external force is applied to it, and the viscosity increases with the increase in shear rate [31][32][33]. The various rheological curves for different types of fluids are shown in Figure 11.…”

Section: Rheological Characteristics Of Debris Flow Slurrymentioning

confidence: 99%

Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method

Niu,

Zhe,

Sun

et al. 2023

Water

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The shear factor of ore drawing is an important factor affecting the formation of underground debris flows. The aim of this study was to investigate the effect of the mining shear factor on underground debris flows in natural caving. The research background was the underground debris flow in the Plan copper mine, and we analyzed the characteristics of the slurry material structure of the underground debris flow, as well as the influence of the ore-drawing shear factor on the formation mechanism of the underground debris flow. The results showed that the slurry of the underground debris flow in the Plan mine is both a pseudoplastic and thixotropic fluid. Shearing force induced in drawing deforms the slurry and decreases its viscosity with the increase in shear rate and time. The shear force produced by the flow of ore particles first produces shear action on the paste in the shear boundary region of the ore drawing, reducing the paste viscosity while increasing its fluidity. Consequently, the “activation” makes the paste flowable, which flows along with the bulk ore flowing through the drawing mouth. The continuous ore-drawing process continuously shears the new moraine slurry in the ore-drawing channel and continuously “activates” the moraine slurry in the ore-drawing channel. Finally, destructive underground debris flow accident of a certain scale occurs. To our knowledge, this study thoroughly investigated the effect of the ore-drawing shear factor on the formation mechanism of underground debris flows, which not only broadens the research field of debris flow but also covers the deficiency of systematic research on underground debris flows, providing theoretical guidance for the prevention and control of underground debris flows.

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“…Because of the need to extrude the GP paste, its rheology is of utmost importance for any AM method, and fortunately, recent work has significantly improved the understanding of GP rheological properties. [14][15][16] The adhesion between layers is also critical but has seen comparatively little investigation for metakaolin-based geopolymers. The only work that was found was that by Archez et al, who evaluated to a small extent the effect of printing delay time on interlayer adhesion.…”

Section: Introductionmentioning

confidence: 99%

“…These steps involve some practical changes to the synthesis process compared to the typical casting route. Because of the need to extrude the GP paste, its rheology is of utmost importance for any AM method, and fortunately, recent work has significantly improved the understanding of GP rheological properties 14–16 . The adhesion between layers is also critical but has seen comparatively little investigation for metakaolin‐based geopolymers.…”

Section: Introductionmentioning

confidence: 99%

Depth dependence of hardness and reaction in metakaolin‐based geopolymers cured at low humidity

Samuel,

Kriven

2023

J Am Ceram Soc.

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Compared to metakaolin‐based sodium and potassium geopolymers cured at 20°C/100% relative humidity, geopolymers which were cured at 20°C/40% relative humidity were found to have considerable changes in the nanoscale structure and physical properties near the surface due to dehydration that occurred before completely hardening. For low‐humidity samples, the density in a thin near‐surface region was higher than the bulk, while porosity and BET specific surface area were greatly diminished. The microhardness at the exposed surface was low but increased sharply within a small depth before decreasing with depth to a constant value, which depended on the initial water content and charge‐balancing cation. 29Si NMR spectroscopy showed that the extent of reaction also varied with distance from the exposed surface. Both the elevated microhardness and incomplete reaction were detected at distances of up to 1.5 cm from the exposed surface, indicating that premature dehydration can cause microstructural changes over length scales that may be significant in large, ambiently cured 3D‐printed geopolymers. These effects are reduced by the use of sodium rather than potassium as the charge‐balancing cation and by raising the initial water content of the geopolymer, although higher water content caused greater surface deformation during drying.This article is protected by copyright. All rights reserved

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Isolating the effects of thixotropy in geopolymer pastes

Cited by 8 publications

References 39 publications

Investigation of geopolymer efflorescence durability problems: Causes and possible solutions

Investigation of geopolymer efflorescence durability problems: Causes and possible solutions

Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method

Depth dependence of hardness and reaction in metakaolin‐based geopolymers cured at low humidity

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