New approach to assess build-up of cement-based suspensions

Mostafa, Ahmed; Yahia, Ammar

doi:10.1016/j.cemconres.2016.03.005

Cited by 116 publications

(47 citation statements)

References 40 publications

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“…Furthermore, the kinetics of structure development in cement and alternative construction materials, both at rest and during processing, are also dependent on the chemical composition and their control is essential for advanced uses including 3D printing. [9][10][11][12][13][14][15] Model systems of the reaction product, the N-A-S-H gel, have been studied to provide insight to the structural development of geopolymer systems. [16][17][18][19][20][21][22] This work focuses on connecting structure-property relationships derived via rheology and neutron scattering to the chemical components and mechanisms responsible for these phenomena.…”

Section: Introductionmentioning

confidence: 99%

“…The chemical composition of these binders, notably Si/Al ratio 5‐7 and type/amount of alkaline ions present, 8 impacts macroscopic properties such as workability and strength, but further research is required to connect to the “geopolymer” formation reaction and microstructure development to increase the utilization of these alternative construction materials. Furthermore, the kinetics of structure development in cement and alternative construction materials, both at rest and during processing, are also dependent on the chemical composition and their control is essential for advanced uses including 3D printing 9‐15 . Model systems of the reaction product, the N‐A‐S‐H gel, have been studied to provide insight to the structural development of geopolymer systems 16‐22 .…”

Section: Introductionmentioning

confidence: 99%

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Relating chemical composition, structure, and rheology in alkali‐activated aluminosilicate gels

2020

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Model aluminosilicate (N-AS -H) gel systems give insight to the complex reaction occurring in alkali-activated binders, allowing for more precise control over chemical composition and exhibiting simpler kinetics. Small angle neutron scattering, oscillatory rheology, and solid-state NMR were used to characterize N-AS -H gel samples and relate structure, chemical composition, and rheology. Aluminum concentration was varied in the gel samples at fixed silica and sodium concentration. Past the percolation point, the gel develops in two regimes distinct in structure and rheological behavior. The first gel regime is characterized by increase in modulus and initial formation of fractal structures following a diffusion-limited monomercluster aggregation mechanism. The second gel regime at higher aluminum concentrations is characterized by a modulus plateau and structure development via reaction-limited aggregation of existing clusters. NMR data indicate a saturation of aluminum in the network at the transition between gel regimes, which may be pH driven. Understanding the structure-property relationships critical to formation of the N-AS -H gel can give valuable insight to the reaction mechanism in alkali-activated binders and the influence of chemical composition on resultant structure and mechanical properties.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Relating chemical composition, structure, and rheology in alkali‐activated aluminosilicate gels

2020

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“…The rheological tests were conducted on a HAAKE MARS III rheometer. It contains a Peltier-type temperature control system, which kept the temperature of samples constant at 23 °C ± 0.1 °C during the tests as conventionally adopted for rheological measurements in cement pastes [33][34][35][36].…”

Section: Rotational Rheometrymentioning

confidence: 99%

Comparison between methods for determining the yield stress of cement pastes

Matos

Pilar

Casagrande

et al. 2019

J Braz. Soc. Mech. Sci. Eng.

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The determination of the yield stress (τ 0) of cement-based materials is of great interest for engineering applications, since it accurately describes the flow behavior and assesses empirical properties related to its workability, such as the slump of concretes and the spreading of mortars. In this work, the τ 0 of cement pastes was determined by different methods. Specifically, pastes with three different water/cement ratios and two supplementary cementitious materials in Portland cement replacement were produced. The mini slump of the pastes was measured, and its static τ 0 and dynamic τ 0 were determined by rotational rheometry. In addition, small amplitude oscillatory shear (SAOS) was used to further investigate the rigidification rate of the pastes over time, providing valuable information for the discussion. The results showed that the dynamic τ 0 values provided by the different rheological models showed strong correlations. However, these values had weaker correlations with the static τ 0. The rest period between the finish of the pre-shear and the test run strongly affected the magnitude of the stress overshoot and therefore the static τ 0 value. SAOS indicated that the decrease in the inter-particle distance increased the rigidification rate of the paste within the first minute after mixing, which may affect the mini slump results. Finally, the use of the mini slump as a single test to generally evaluate cement pastes with wide ranges of flowability may not be adequate, in line with the existence of different tests for the evaluation of conventional and self-compacting concretes.

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“…9,[11][12][13] Furthermore, by accelerating the nucleation and growth rates of CSH using chemical admixtures and minerals, the development rate of elasticity can be observably increased. 11,[14][15][16][17][18][19] However, the role of crystalline phases, such as ettringite and calcium hydroxide, in the evolution of elasticity is not well understood, and the relationship between the formation and growth processes of CSH and the elasticity evolution of cement paste has not been proved by sufficiently detailed experimental observations.…”

Section: Introductionmentioning

confidence: 99%

“…Small amplitude oscillatory shear (SAOS) has been successfully developed to nondestructively investigate the evolution of the elasticity of cement paste in situ. 9,11,17,[20][21][22][23] In SAOS, a strain smaller than the critical strain of cement paste is applied for a continuous sinusoidal excitation to obtain a stress response. Yuan stated that the critical strain ranges from 10 −5 to 10 −4 for cement paste.…”

Section: Introductionmentioning

confidence: 99%

Evolution of elastic behavior of alite paste at early hydration stages

et al. 2020

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Elastic behavior is an important aspect of fresh cement‐based materials. In this paper, the elasticity development of fresh pure alite paste within 5 hours was monitored in situ by small amplitude oscillation shear. Isothermal microcalorimetry, X‐ray diffraction, scanning electronic microscopy, 1H nuclear magnetic resonance, zeta potential measurements were used to investigate the underlying mechanisms. It was found that the evolution of storage modulus can be characterized by three different stages. The first stage stems from the compression of electrical double layer and the slight increase of solid volume fraction; the second stage is only controlled by the colloidal interaction; and the third stage is associated to the significant growth of solid volume fraction, the enhancement of short‐range attraction and the rigidification of calcium silicate hydrate (CSH) network. Moreover, the relationship between the formation of CSH and the growth of elasticity was also quantified.

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New approach to assess build-up of cement-based suspensions

Cited by 116 publications

References 40 publications

Relating chemical composition, structure, and rheology in alkali‐activated aluminosilicate gels

Relating chemical composition, structure, and rheology in alkali‐activated aluminosilicate gels

Comparison between methods for determining the yield stress of cement pastes

Evolution of elastic behavior of alite paste at early hydration stages

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