Shifting factor—A new paradigm for studying the rheology of cementitious suspensions

Mantellato, Sara; Flatt, Robert J.

doi:10.1111/jace.17040

Cited by 25 publications

(6 citation statements)

References 42 publications

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“…This allows us to estimate a local critical stress scale for desorption σ * 0 = E/R 3 g ∼ 10 6 Pa, which can be converted into the area of contact when friction is turned on, r 2 0 , by equating the bulk and local forces, σ * 0 r 2 0 ∼ σ * d 2 , for particles of linear size d. This gives r 0 ∼ 7 nm, which is plausibly the length scale of surface roughness; so the picture is that σ * is the external stress needed to drive adsorbed PAA from asperities, exposing these to interact frictionally. This highlights the role of surfactant adsorption at the local level, as raised by Mantellato and Flatt (2020) for partial coverage of superplasticiser in cementitious suspensions.…”

Section: Surfactantmentioning

confidence: 88%

Turning a yield-stress calcite suspension into a shear-thickening one by tuning inter-particle friction

2020

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We show that a suspension of non-Brownian calcite particles in glycerol-water mixtures can be tuned continuously from being a yield-stress suspension to a shear-thickening suspension—without a measurable yield stress—by the addition of various surfactants. We interpret our results within a recent theoretical framework that models the rheological effects of stress-dependent constraints on inter-particle motion. Bare calcite particle suspensions are found to have finite yield stresses. In these suspensions, frictional contacts that constrain inter-particle sliding form at an infinitesimal applied stress and remain thereafter, while adhesive bonds that constrain inter-particle rotation are broken as the applied stress increases. Adding surfactants reduces the yield stress of such suspensions. We show that, contrary to the case of surfactant added to colloidal suspensions, this effect in non-Brownian suspensions is attributable to the emergence of a finite onset stress for the formation of frictional contacts. Our data suggest that the magnitude of this onset stress is set by the strength of surfactant adsorption to the particle surfaces, which therefore constitutes a new design principle for using surfactants to tune the rheology of formulations consisting of suspensions of adhesive non-Brownian particles.

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Section: Surfactantmentioning

confidence: 88%

Turning a yield-stress calcite suspension into a shear-thickening one by tuning inter-particle friction

2020

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“…However, we may assume that the concrete yield stress changes proportionally to the change in the paste yield stress, which, in turn, is conditioned by its water loss. The paste yield stress change can be estimated from [22] and is found to increase by a factor 1.7 for the above example. To qualify what this represents in terms of slump loss, we use the expression proposed by Roussel et al relating yield stress to slump [42].…”

Section: Rheological Properties Of Recycled Concretementioning

confidence: 94%

Challenges in material recycling for postwar reconstruction

et al. 2022

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Besides the fact that concrete recycling allows to avoid landfills disposal and contributes to a closed-cycle economy, such option may be very much in demand in war struck regions such as Ukraine, which after the end of the war, are faced with the problem of rebuilding and reconstructing. Beyond this emergency, even in peacetime extensive parts of the building stock will sooner or later need to be replaced and concrete recycling is called to play an increasing role there. However, depending on the technology and degree to which aggregates are recycled, concrete may be characterized by poor workability, reduced mechanical properties, increased shrinkage and reduced durability. This deterioration in the properties of recycled concrete is usually attributed to the characteristics of the old cement mortar remaining on the surface of the recycled aggregates, which is best considered as an additional volume of hardened cement paste with fine aggregate and additional porosity. This article attempts to underline how such key concepts help frame the current state of knowledge about concrete recycling, understand the implications of existing regulations, in order to define pragmatic and efficient routes for broadening the use of concrete recycling in war struck regions, with specific examples regarding Ukraine.

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“…Steric interactions scale with the amount of adsorbed PCE when there is incomplete surface coverage [29]. The most appropriate representation for this is the adsorbed mass with respect to the specific surface area of the particles (4), as the interaction between PCE and the hydration reaction can affect the kinetics and thus the specific surface area [30].…”

Section: Polymer Structure and Dispersing Propertiesmentioning

confidence: 99%

Rheology of low‐clinker suspensions: Multiscale comparison of the effect of PCE on thixotropy

Nicia,

Fobbe,

Jansen

et al. 2023

ce papers

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Addressing climate change requires reducing the carbon footprint of cement‐based building materials on a global scale. One promosing approach involves decreasing the clinker content by incorporating fine supplementary cementitious materials (SCM), which, however, can increase the stickiness of fresh concrete. Along with viscosity, thixotropic structural build‐up is a critical rheological parameter that impacts the stickiness of the SCM‐rich suspensions. Thus, it is essential to gain a precise understanding of how the molecular structure and mode of addition of polycarboxylate ethers (PCE) affect the thixotropic structural build‐up in low‐clinker suspensions. To address this issue, we investigate key parameters affecting thixotropy, specifically PCE adsorption and early hydration kinetics at the cement paste and mortar level, using a multiscale approach. In an application‐oriented concept, we maintain a constant yield stress by varying the PCE dosage to achieve constant workability. Our results demonstrate that higher thixotropy correlates with increased PCE charge density and direct addition in cement pastes and mortars. Moreover, it is indicated that increasing specific surface area and ettringite contents promote additional thixotropy‐enhancing mechanisms.

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Shifting factor—A new paradigm for studying the rheology of cementitious suspensions

Cited by 25 publications

References 42 publications

Turning a yield-stress calcite suspension into a shear-thickening one by tuning inter-particle friction

Turning a yield-stress calcite suspension into a shear-thickening one by tuning inter-particle friction

Challenges in material recycling for postwar reconstruction

Rheology of low‐clinker suspensions: Multiscale comparison of the effect of PCE on thixotropy

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