The nano-mechanical signature of Ultra High Performance Concrete by statistical nanoindentation techniques

Sorelli, Luca; Constantinides, Georgios; Ulm, Franz Josef; Toutlemonde, François

doi:10.1016/j.cemconres.2008.09.002

Cited by 461 publications

(163 citation statements)

References 20 publications

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“…For the repair matrix, with a w/c ratio of 0.4, at the age of 28 days, large amounts of unhydrated cement particles locally contribute to higher stiffness values. This stiffening role of the residual, unhydrated clinker on the properties of the hardened cement paste was noted in previous studies (Sorelli et al 2008). Stiffness values obtained in the numerical simulation are somewhat higher than the stiffness values obtained by the UVP measurements at the age of 28 days.…”

Section: Simulation Results and Discussioncontrasting

confidence: 37%

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Luković

Šavija

Dong

et al. 2014

ACT

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Micromechanical interface properties in a concrete repair system determine the performance and reliability of a repaired structure. In order to characterize these properties, nanoindentation technique was applied. Three different repair material mixtures, based on Portland cement or partial replacement of Portland cement with blast furnace slag, were tested. Hardness and elastic modulus values obtained from the nanoindentation were used directly as input for simulated direct tension test. This way, the fracture behaviour of original microstructure, "mimicked" by Delft lattice model, is analysed. Backscattered electron (BSE) image analysis is utilized to estimate the average size of the interface zone which is distinguished as locally more porous area. This, together with simulation results, is further used for calculation of the interface stiffness. Simulation results enable prediction and better insight into fracture propagation and micromechanical response of the tested zone. They also indicate the ratio between interface and bulk material fracture properties when different types of repair materials are used. Load displacement diagrams of interface, old and new material can serve as an input for numerical modelling and understanding of fracture behaviour of the repair systems at the higher scale. Potentially, this approach may develop as a tool for verifying and engineering interface properties such that desired performance of the repaired structure is achieved.

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Section: Simulation Results and Discussioncontrasting

confidence: 37%

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Luković

Šavija

Dong

et al. 2014

ACT

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“…This difference is attributed to the magnification used (250x) in the present experiments. It has been reported that low magnification can prevent the dissociation of the peak of CH [39]. However, the shape of calcium hydroxide phase and its hardness differs from the C-S-H. Quartz and silica fume also exhibit similar gray level to C-S-H.…”

Section: Discussionmentioning

confidence: 88%

Microstructure and hardness of cement pastes with mineral admixture

et al. 2017

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Portland cement pastes are highly heterogeneous material and exhibits heterogeneous features over a wide range of length scales. Mechanical properties of microstructure can be determined using depth-sensing indentation. Coupled indentation/SEM technique can be used to location the indents and provides a way to determine the mechanical properties of a specific phase. Thus, the present paper aims to determine the hardness of different phases of cement pastes prepared with different mineral admixtures including sugarcane bagasse ash. The microstructure of cement pastes prepared with different mineral admixtures is analyzed by X ray diffraction, scanning electron microscopy and dynamic hardness tests on polished sections. The different backscatter coefficient allows to differentiate anhydrous phases from C-S-H, calcium hydroxide, silica fume and quartz. A grid of indentation is used to determine the hardness of the different phases and a complete phase segmentation of the different samples is achieved. The results show that the hardness of the different phases follow the sequence (from higher to lower hardness) quartz, anhydrous particles, calcium hydroxide, C-S-H and agglomerated silica fume. The presence of agglomerated silica fume is clearly observed in scanning electron microscopy images and the poor mechanical properties of these areas might compromise the cement pastes. The microstructure of cement pastes prepared with sugarcane bagasse ashes is similar to the observed in samples with crushed quartz.

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“…(1/κ)−1 (8) Where the operator · is such that x = 1/2 (x + |x|) ∀x ∈ R. The characteristic time τ X,0 related to this kinetic law is equal to 1/(κ X k X ) where κ X is the reaction order and k X , a constant rate.…”

Section: Kineticmentioning

confidence: 99%

“…Recently, continuum micromechanics models have been used in many successful assessments of the effective mechanical properties of hardened cement-based materials [5][6][7][8]. The extension of these models to take into account the poroelastic behavior of concrete materials [1,9,10] introduced several model applications [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

Venkovic¹,

Sorelli²,

Sudret³

et al. 2013

Probabilistic Engineering Mechanics

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The durability of concrete materials with regard to early-age volume changes and cracking phenomena depends on the evolution of the poroelastic properties of cement paste. The ability of engineers to control the uncertainty of the percolation threshold and the evolution of the elastic modulus, the Biot-Willis parameter and the skeleton Biot modulus is key for minimizing the vulnerability of concrete structures at early-age. This work presents original results on the uncertainty propagation and the sensitivity analysis of a multiscale poromechanics-hydration model applied to cement pastes of water-to-cement ratio of 0.40, 0.50 and 0.60. Notably, the proposed approach provides poroelastic properties required to model the behavior of partially saturated aging cement pastes (e.g. autogenous shrinkage) and it predicts the percolation threshold and undrained elastic modulus in good agreement with experimental data. The development of a stochastic metamodel using polynomial chaos expansions allows to propagate the uncertainties of kinetic parameters of hydration, cement phase composition, elastic moduli and morphological parameters of the microstructure. The presented results show that the propagation does not magnify the uncertainty of the single poroelastic properties although, their correlation may amplify the variability of the estimates obtained from poroelastic state equations. In order to reduce the uncertainty of the percolation threshold and that of the poroelastic properties at early-age, engineers need to assess more accurately the apparent activation energy of calcium aluminate and, later on, of the elastic modulus of low density calcium-silicate-hydrate.

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The nano-mechanical signature of Ultra High Performance Concrete by statistical nanoindentation techniques

Cited by 461 publications

References 20 publications

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Microstructure and hardness of cement pastes with mineral admixture

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

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