Hardness–packing density scaling relations for cohesive-frictional porous materials

Cariou, Sophie; Ulm, Franz‐Josef; Dormieux, Luc

doi:10.1016/j.jmps.2007.06.011

Cited by 76 publications

(51 citation statements)

References 56 publications

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“…The indentation results were linked together with chemistry information of Ca, Si, Al, and Fe acquired by backscattered images and elemental maps using an image-processing algorithm to assure one-to-one spatial correlation (60). The packing fraction distribution of the C-S-H gel is then determined following the micromechanics approach (64)(65)(66) by isolating C-S-H in the coupled indentation-chemistry analysis assuming C-S-H particle stiffness to be 72 ± 3 GPa (8). Technical details are discussed in SI Appendix.…”

Section: Methodsmentioning

confidence: 99%

Mesoscale texture of cement hydrates

Ioannidou

Krakowiak

Bauchy

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water.Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials.U pon dissolution of cement powder in water, calcium-silicate-hydrates (C-S-H) precipitate and assemble into a cohesive gel that fills the pore space in the cement paste over hundreds of nanometers and binds the different components of concrete together (1). The mechanics and microstructure are key to concrete performance and durability, but the level of understanding needed to design new, more performant cements and have an impact on the CO 2 footprint of the material is far from being reached (2).Most of the experimental characterization and models used to predict and design cement performance have been developed at a macroscopic level and hardly include any material heterogeneity over length scales smaller than micrometers (3). However, EM imaging, nanoindentation tests, X-rays and neutron scattering, and NMR analysis as well as atomistic simulations have now elucidated several structural and mechanical features concentrated within a few nanometers (4-8). The hygrothermal behavior of cement suggests a hierarchical and complex pore structure that develops during hydration and continues to evolve (1, 9-11). NMR and small-angle neutron scattering (SANS) studies of hardened C-S-H identified distinctive features of the complex pore network and detected significant structural heterogeneities spanning length scales between tens and hu...

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Section: Methodsmentioning

confidence: 99%

Mesoscale texture of cement hydrates

Ioannidou

Krakowiak

Bauchy

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

206

146

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“…Porous materials with a dominating matrix-pore inclusion morphology are well represented by the Mori-Tanaka and Self-Consistent schemes, as seen in [2] and [3]. In MoriTanaka scheme some material parameters such as α d , σ 0 , α m are calculated and they include the soil cohesion, porosity and friction angle effects.…”

Section: Porous Materialsmentioning

confidence: 99%

“…where α d , σ 0 , α m are material parameters and calculated as seen in [2] and [3], J 2 is associated to deviatory stress and Σ m is mean stress.…”

Section: Porous Materialsmentioning

confidence: 99%

“…The challenge is to quantify the interaction of this many variables into a yield function, important to predict the plastic behavior of the material. The works of [2] and [3] have given a valuable contribution in the development of an yield criterion. This formulation is derived from a micro or nano scale study of solid and porous phases of the materials.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Limit Analysis on Scratch Test Problem

Figueiredo¹,

Borges²

2014

Proceedings of 10th World Congress on Computational Mechanics

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Abstract. Scratch test is one of the oldest method to determine mechanical properties in materials. The technique has gained interest due to the properties implied during test, such as adherence, hardness, cohesion and elasticity. On this test a rigid indenter is dragged on the material test surface at a constant depth and controlled forces. This problem is modeled by finite elements method and limit analysis theory, which is is a direct method and there is no need to calculate stresses during each load step in order to compute critical states and collapse mechanisms. From virtual power principle, the internal power is related to the external power, which is amplified by load factor so that the body achieves a plastic collapse. The solution of a limit analysis problem is to find this load factor, the plastically admissible stresses fields that are in equilibrium with the given forces system, the kinematically admissible velocity fields, the strain rate field , which is related to the velocity field by means of a deformation operator, and the plastic multiplier. The solution of a limit analysis problem closely depends on the yield function that describes the behavior of a material, such as von Mises for metals and Drucker-Prager for rocks. However, traditional criteria for rocks and soils such as MohrCoulomb and Drucker-Prager do not consider material porosity. Therefore, an yield criterion that includes porosity effect is applied in this work. This function is applied to the discretized limit analysis model. A semi-analytical solution based on limit analysis lower bound method is developed and the proposed yield function is also applied. Then, the results between both methods are compared.

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“…1. [3,11] The negligible effect of the particle shape on the homogenized mechanical properties largely simplifies the micromechanical analysis. It thus suffices, to consider spherical particles and a distinct disordered morphology of the solid phase, similar to a polycrystal, characterized by a solid percolation threshold of η 0 = 0.5.…”

Section: Does Particle Shape Matter? [34]mentioning

confidence: 99%

Nano-Engineering of Concrete

Ulm

2012

Arab J Sci Eng

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This paper summarizes recent developments in the field of nanoindentation analysis of highly heterogeneous composites. The fundamental idea of the proposed approach is that it is possible to assess nanostructure from the implementation of micromechanics-based scaling relations for a large array of nanoindentation tests on heterogeneous materials. We illustrate this approach through the application to calcium-silicate-hydrate (C-S-H), the binding phase of all cement-based materials. For this important class of materials, we show that C-S-H exists in at least three structurally distinct but compositionally similar forms: low density, high density and ultra-high density. These three forms differ merely in the packing density of 5-nm sized particles. The proposed approach also gives access to the solid particle properties of C-S-H, which can now be compared with results from atomistic simulations. By way of conclusion, we show how this approach provides a new way of analyzing complex hydrated nanocomposites, in addition to classical microscopy techniques and chemical analysis. This approach will turn out invaluable in our quest of adding the necessary "green" value to a commodity, concrete, by nano-engineering higher strength and toughness from first principles.

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Hardness–packing density scaling relations for cohesive-frictional porous materials

Cited by 76 publications

References 56 publications

Mesoscale texture of cement hydrates

Mesoscale texture of cement hydrates

Limit Analysis on Scratch Test Problem

Nano-Engineering of Concrete

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