Surface roughness criteria for cement paste nanoindentation

Miller, Mahalia; Bobko, Christopher P.; Vandamme, Matthieu; Ulm, Franz‐Josef

doi:10.1016/j.cemconres.2007.11.014

Cited by 375 publications

(136 citation statements)

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“…Since analysis of nanoindentation experiments assume that the indentation occurs on a flat surface, smoothening the surface and reducing the roughness to a tolerable level is critical for receiving accurate results [31]. Therefore, once each mixture was fully cured, the center part of…”

Section: Specimen Preparationmentioning

confidence: 99%

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

Khedmati

Kim

Turner

et al. 2018

Materials Characterization

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Abstract:Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region because it acts as a bridge transferring forces between aggregates and a binding matrix and is generally susceptible to damage. As alternative binding agents like alkali-activated precursors have obtained substantial attention in recent years, there is a growing need for fundamental knowledge to uncover interphase formation ACCEPTED MANUSCRIPTA C C E P T E D M A N U S C R I P T mechanisms. In this paper, two different types of binding materials, i.e., fly ash-based geopolymer and ordinary portland cement, were mixed with limestone aggregate to examine and compare the microstructures and nanomechanical properties of interphase region. To this end, microstructural characteristics using scanning microscopies, nanomechanical properties by nanoindentation tests, and spatial mapping of chemical contents based on the energy dispersive spectroscopy were integrated to identify and investigate the interphase region formed by the case-specific interactions between the matrix materials and limestone. The integrated microstructural-nanomechanicalchemical approach was effective to better understand links between material-specific properties of cementing phases. More specifically, the fly ash-based geopolymer paste was usually well bonded to the aggregate surface with a rich formation of N-A-S-H gel, while interfacial debonding was often observed between aggregate surface and paste in ordinary portland cement concrete. However, when a good bonding between aggregate and paste is formed, interphase region in PCC didn't show any considerable difference in nanomechanical properties compared to the bulk paste. ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T An Integrated Microstructural-Nanomechanical-Chemical Approach to Examine MaterialSpecific Characteristics of Cementitious Interphase Regions Abstract:Effective properties and structural performance of cementitious mixtures are substantially governed by the quality of the interphase region because it acts as a bridge transferring forces between aggregates and a binding matrix and is generally susceptible to damage. As alternative binding agents like alkali-activated precursors have obtained substantial attention in recent years, there is a growing need for fundamental knowledge to uncover interphase formation mechanisms. In this paper, two different types of binding materials, i.e., fly ash-based geopolymer and ordinary portland cement, were mixed with limestone aggregate to examine and compare the microstructures and nanomechanical properties of interphase region. To this end, microstructural characteristics using scanning microscopies, nanomechanical properties by nanoindentation tests, and spatial mapping of chemical contents based on the energy dispersive spectroscopy were integrated to identify and investigate the interphase region formed by the case-specific interactions between the matrix materials and limestone. The...

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Section: Specimen Preparationmentioning

confidence: 99%

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

Khedmati

Kim

Turner

et al. 2018

Materials Characterization

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“…They differed by their water-to-cement (w/c) mass ratio ranging from w/c ϭ 0.15 to w/c ϭ 0.40, heat treatment, and mineral additions, including silica fumes and calcareous fillers. The samples were prepared according to a procedure described in a previous study (20). On each sample 2 series of statistical nanoindentation tests were carried out that differ in the loading protocol: the first series assesses the microstructure from indentation hardness and indentation stiffness results; obtained by a trapezoidal load history with a maximum load of P max ϭ 2 mN, applied in 10 s, kept constant over 5 s and unloaded in 10 s. Following fast loading, the 5-s dwelling time is short enough to ensure that the indentation hardness, H ϭ P max /A c (with A c the projected area of contact between the indenter probe and the indented surface), is representative of the strength content (19,23,24).…”

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confidence: 99%

Nanogranular origin of concrete creep

Vandamme

Ulm

2009

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

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379

192

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Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium-silicate-hydrates (C-S-H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C-S-H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C-S-H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (Ϸ1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years.C oncrete is the most-used construction material on earth. The annual worldwide production stands at 20 billion tons and increases per annum by 5%. However, the fundamental causes of concrete creep are still an enigma, and have deceived many decoding attempts from both experimental (1-3) and theoretical sides (4-8). In the United States alone, concrete creep is partly responsible for an estimated 78.8 billion dollars required annually for highway and bridge maintenance. Although it is generally agreed that the complex creep behavior of concrete materials is largely related to the viscoelastic response of the primary hydration product and binding phase of hardened Portland cement paste, the calcium-silicate-hydrate (C-S-H), the creep properties of C-S-H have never been measured directly. C-S-H precipitates when cement and water are mixed, as clusters of nanoscale colloidal particles (9, 10) that cannot be recapitulated ex situ in bulk form suitable for macroscopic testing. Over decades, therefore, concrete creep properties have been probed on the composite scale of mortar and concrete (11), with the conclusion that there are 2 distinct creep phenomena at play ( Fig. 1 A and B): a short-term volumetric creep and a long-term creep associated with shear deformation (3,7,12,13), with a creep rate evolving as a power function t Ϫn of exponent n between 0.9 and 1 (14). The assessment of this long-term creep is most critical for the durability of concrete structures, and requires, for a specific concrete composition and structural application, years of expensive macroscopic testing (11,14). After more than 40 years of research (4-8), basic questions persist regarding the physical origin of this logarithmic creep and its link with microstructure and composition.In this study, we investiga...

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“…To prepare the flat surface required for nanoindentation, the sample was fixed on a steel support, coarsely ground with Si-C paper, then polished on a lapping wheel impregnated with 1-µm diamond paste 23 . The sample was subsequently cleaned with n-decane in an ultrasonic bath for five minutes.…”

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confidence: 99%

A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)₂ Nanocomposites

Chen

Sorelli

Vandamme

et al. 2010

Journal of the American Ceramic Society

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295

122

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Surface roughness criteria for cement paste nanoindentation

Cited by 375 publications

References 19 publications

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

Nanogranular origin of concrete creep

A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)₂ Nanocomposites

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Surface roughness criteria for cement paste nanoindentation

Cited by 375 publications

References 19 publications

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

An integrated microstructural-nanomechanical-chemical approach to examine material-specific characteristics of cementitious interphase regions

Nanogranular origin of concrete creep

A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)2 Nanocomposites

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A Coupled Nanoindentation/SEM‐EDS Study on Low Water/Cement Ratio Portland Cement Paste: Evidence for C–S–H/Ca(OH)₂ Nanocomposites