Structural model of gelation processes of a sodium silicate sol destabilized by calcium ions: combination of SAXS and rheological measurements

Gaboriaud, Fabien; Nonat, André; Chaumont, Denis; Craievich, A. F.

doi:10.1016/j.jnoncrysol.2004.11.019

Cited by 21 publications

(12 citation statements)

References 15 publications

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“…Moreover, self‐similarity over at least a few scales can be assessed when the log–log plot shows a linear trend. Within the q ‐range of interest, the q ‐dependence of the SAXS intensity is simply given by:

I false(q false) \propto q^{- d_{m}^{normalSAXS}} with false(d_{e} - 2 false) \leq d_{m}^{normalSAXS} \leq d_{normale}

…”

Section: Resultsmentioning

confidence: 99%

Evidence of a Fractal Percolating Network During Geopolymerization

Rouyer

Poulesquen

2015

J. Am. Ceram. Soc.

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This study focuses on the transition from the paste state to the solid state which occurs during the hardening of metakaolinbased Na-geopolymers. The occurrence of primary interactions and the structural properties were investigated using classical oscillatory rheology (OR) methods. A time-frequency-resolved rheology (TF2R) method was used in order to obtain more detailed information about the percolation and aggregation mechanisms. The results obtained show the occurrence of the following process: (i) Elastic behavior predominates initially over the viscous behavior at low frequency. (ii) A percolating process then takes place when the viscoelastic parameters become parallel over more than two frequency decades. At the gel point, a mass-fractal dimension of approximately 2 was determined. (iii) During the formation of the porous network, the viscous behavior predominates over the elastic one due to the occurrence of polycondensation reactions. (iv) Lastly, a solid state is reached, where the elastic modulus shows a plateau and the viscous modulus decreases. These macroscopic mechanical results are compared using the small angle x-ray scattering technique. Scattering experiments were in complete agreement with the rheological measurements and showed the presence of aggregated oligomers and a mass fractal dimension equal to 2.1 at the gel point, increasing up to a surface fractal dimension reflecting the formation of the mesoporous network.

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I false(q false) \propto q^{- d_{m}^{normalSAXS}} with false(d_{e} - 2 false) \leq d_{m}^{normalSAXS} \leq d_{normale}

…”

Section: Resultsmentioning

confidence: 99%

Evidence of a Fractal Percolating Network During Geopolymerization

Rouyer

Poulesquen

2015

J. Am. Ceram. Soc.

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“…Hence, it is possible that the effective bulk modulus of the gel during cracking is closer to high values such as reported by Phair. Moreover, the different sorts of gel that are produced in different chemical environments might also have very different and time-dependant values of these parameters as observed on the storage and loss moduli of synthetic alkaline-calcium silica gels by Gaboriaud [9]. Since the swelling of the gel is often explained by water absorption, they might also differ significantly according to the saturation degree of the concrete.…”

Section: Numerical Results: Effect Of Aggregate Size On Crack Initiatmentioning

confidence: 99%

A computational linear elastic fracture mechanics-based model for alkali–silica reaction

Charpin

Ehrlacher

2012

Cement and Concrete Research

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A fracture mechanics model for alkali-silica reaction (ASR) is presented that deals with the case of a concrete made up of dense spherical aggregates. Chemistry and diffusion (of ions and gel) are not modelled. The focus is put on the mechanical consequences of the progressive replacement of the aggregates by a less dense gel. A ring-shaped crack then appears in the cement paste depending on the pressure build-up, according to an incremental energy criterion. The stored elastic energy and deformation of each configuration are determined assuming that each aggregate is embedded in an infinite cement paste matrix, through Finite Element Analysis. We note a very different behaviour of aggregates of different sizes. Adding the contributions of different aggregates leads to an estimate of the free expansion of a concrete of given aggregate size distribution. Parameters of the model are identified, providing a good fit to experiments taken from Multon's work.

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“…It should be noted that this work did not consider the possibility of alkali silicate activators; this concept was introduced and developed later by Glukhovsky [9], but has proven to be the basis of much of the subsequent research in alkali-activation due to the faster strength development achieved in these systems. Some later authors have actually considered Ca(OH)2 as a retarder in silicate-activated slag binders when added directly into the activating solution [14], but this is more likely to be because it introduces a reduction in the effectiveness of the activator through precipitation of silicate gel in colloidal particles [15] rather than a true retardation effect in the binder. Figure 1.…”

Section: The Work Of Purdon Revisitedmentioning

confidence: 99%

Milestones in the analysis of alkali-activated binders

Provis

Bernal

2014

Journal of Sustainable Cement-Based Materials

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The use of alkali activation to achieve environmental savings in the production of construction materials is currently an extremely active area of research and development. There is now a diverse range of chemistries and applications that have been developed within the broader theme of 'alkali-activated materials', including the subclass of lower-calcium binders which are also known as 'geopolymers'. Academic research and commercial development have combined to bring these materials to a level of technological maturity where larger-scale deployment is now taking place. This paper reviews some of the key aspects of alkali-activation technology which have brought the field to this point, with a particular view towards re-assessing key points and comments which have been raised in several historical reviews and discussions of this class of materials. Conclusions are therefore drawn regarding which among these key questions have been answered, and which remain outstanding in an engineering or scientific sense.

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Structural model of gelation processes of a sodium silicate sol destabilized by calcium ions: combination of SAXS and rheological measurements

Cited by 21 publications

References 15 publications

Evidence of a Fractal Percolating Network During Geopolymerization

Evidence of a Fractal Percolating Network During Geopolymerization

A computational linear elastic fracture mechanics-based model for alkali–silica reaction

Milestones in the analysis of alkali-activated binders

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