@article {575, title = {Le Ch{\^a}telier{\textquoteright}s conjecture: Measurement of colloidal eigenstresses in chemically reactive materials}, journal = {Journal of the Mechanics and Physics of Solids}, volume = {112}, year = {2018}, month = {Mar-2018}, pages = {334 - 344}, abstract = {

Volume changes in chemically reactive materials, such as hydrating cement, play a critical role in many engineering applications that require precise estimates of stress and pressure developments. But a means to determine bulk volume changes in the absence of other deformation mechanisms related to thermal, pressure and load variations, is still missing. Herein, we present such a measuring devise, and a hybrid experimental-theoretical technique that permits the determination of colloidal eigenstresses. Applied to cementitious materials, it is found that bulk volume changes in saturated cement pastes at constant pressure and temperature conditions result from a competition of repulsive and attractive phenomena that originate from the relative distance of the solid particles- much as Henry Louis Le Chatelier, the father of modern cement science, had conjectured in the late 19th century. Precipitation of hydration products in confined spaces entails a repulsion, whereas the concurrent reduction in interparticle distance entails activation of attractive forces in charged colloidal particles. This cross-over from repulsion to attraction can be viewed as a phase transition between a liquid state (below the solid percolation) and the limit packing of hard spheres, separated by an energy barrier that defines the temperature-dependent eigenstress magnitude. (C) 2017 Elsevier Ltd. All rights reserved.

Fig. 1. Pressure vessel measurement device for volume changes under constant pressure{\textellipsis}

Fig. 2. Bulk Volume Change measurement results under drained and fluid saturated{\textellipsis}

Fig. 3. Eigenstress Scaling: (a) Normalized eigenstress (|σ*|/max|σ*|) vs

Fig. 4. Eigenstress interpretation: (a) volume fractions vs

}, keywords = {Poromechanics; Colloidal stresses; Cement-based materials; Expansion; Shrinkage}, issn = {00225096}, doi = {10.1016/j.jmps.2017.12.012}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0022509617309985}, author = {Muhannad Abuhaikal and Katerina Ioannidou and Petersen, Thomas and Roland Jean-Marc Pellenq and Franz-Josef Ulm} } @article {247, title = {Evolution of organo-clay composites with respect to thermal maturity in type II organic-rich source rocks}, journal = {Geochimica et Cosmochimica Acta}, volume = {195}, year = {2016}, month = {Dec-15-2016}, pages = {68 - 83}, abstract = {

Among the proposed pathways of sequestration and progressive transformation of organic matter (OM) during burial, the sorptive protection mechanism explains the strong relationship between total organic carbon (TOC) and mineral surface area (MSA) noted in numerous black shales around the globe. The complete mechanistic framework of preservation and evolution of OM in organo-mineral complexes remains, however, an enigma. On one hand, smectite layers composing the clay fraction are known to have a major influence on available surface area. OM maturation occurs, on the other hand, concurrently with the smectite illitization that provokes the closure of the interlayer spaces. The potential of smectite layers in the sequestration and preservation of organic molecules and the fate of these molecules with respect to the smectite illitization were therefore addressed. Here, the mineralogy of three organic-rich source rocks of various maturities was characterized in regards with the geochemistry of their OM. A thorough examination of the clay minerals present in the clay matrices provided evidences of mixed layer minerals containing smectite and illite layers with an increasing illite component with respect to maturity. The comprehensive interpretation of the X-ray diffractograms and analytical electron microscopy results suggested the presence of organic molecules in the inter-particulate and possibly the interlayer spaces of the smectite-rich components in immature source rocks. This eventuality was further supported by the presence of intercalated clay-organic nanocomposites observed by transmitted electron microscopy coupled with energy dispersive spectroscopy. Textural observations also showed that the increased illite content found in the overmature sample led to the reorganization of the OM and the clay particles into nano-scale aggregates. These results clarify the geochemical mechanism beyond the reported relationship between TOC and MSA and allow generalizing it to various organic-rich source rocks. Eventually, the understanding of the close organo-clay association raises prospects on the prediction of the evolution of the mechanical properties of economically valuable source rocks with respect to maturity.

}, issn = {00167037}, doi = {10.1016/j.gca.2016.09.008}, author = {Berthonneau, Jeremie and Grauby, Olivier and Muhannad Abuhaikal and Roland Jean-Marc Pellenq and Franz-Josef Ulm and Henri Van Damme} } @proceedings {100, title = {Poro-chemo-fracture-mechanics ... bottom-up: Application to risk of fracture design of oil and gas cement sheath at early ages}, journal = {Euro-C Conference}, volume = {COMPUTATIONAL MODELLING OF CONCRETE STRUCTURES, VOL 1 }, year = {2014}, month = {Jan-2014}, pages = {61-67}, publisher = {CRC PRESS-TAYLOR \& FRANCIS GROUP}, address = {MAR 24-27, 2014, St Anton am Alberg, AUSTRIA}, abstract = {

With ever more challenging (T, p) environments for cementing applications in oil and gas wells, there is a need to change the classical paradigm of constitutive modeling of the early-age behavior of cementitious materials in oil-and gas well applications. Herein, we propose a bottom-up approach, which starts at the molecular scale of calcium-silicate-hydrates (C-S-H), and propagates this understanding via incremental poroelastic upscaling methods to the meso-and macroscale, and ultimately to the scale of engineering applications. With a clear focus on engineering risk-of-fracture evaluations, we show how to integrate this bottom-up approach with fracture mechanics.

}, isbn = {978-1-138-02641-4; 978-1-315-76203-6}, doi = {10.1201/b16645-8}, author = {Franz-Josef Ulm and Muhannad Abuhaikal and Thomas Alexander Petersen and Roland Jean-Marc Pellenq}, editor = {Bicanic, N and Mang, H and Meschke, G and DeBorst, R} }