@article {150, title = {Nano-chemo-mechanical signature of conventional oil-well cement systems: Effects of elevated temperature and curing time}, journal = {Cement and Concrete Research}, volume = {67}, year = {2015}, month = {Jan-2015}, pages = {103 - 121}, abstract = {

With ever more challenging (T,p) environments for cementing applications in oil and gas wells, there is a need to identify the fundamental mechanisms of fracture resistant oil well cements. We report results from a multi-technique investigation of behavior and properties of API class G cement and silica-enriched cement systems subjected to hydrothermal curing from 30\ \°C to 200\ \°C; including electron probe microanalysis, X-ray diffraction, thermogravimetry analysis, electron microscopy, neutron scattering (SANS), and fracture scratch testing. The results provide a new insight into the link between system chemistry, micro-texture and micro-fracture toughness. We suggest that the strong correlation found between chemically modulated specific surface and fracture resistance can explain the drop in fracture properties of neat oil-well cements at elevated temperatures; the fracture property enhancement in silica-rich cement systems, between 110\° and 175\ \°C; and the drop in fracture properties of such systems through prolonged curing over 1\ year at 200\ \°C.

Fig.1. Particle size distribution of the silica flour (ground quartz) incorporated{\textellipsis}

Fig.2. Location of the {\textquotedblleft}chemical poles{\textquotedblright} of the cement clinker and cement hydration{\textellipsis}

Fig.3. Simplified schematic of: (a) the cement paste microstructure cured at room{\textellipsis}

Fig.4. A schematic of the effect of adding an extra dimension, Al, to the statistical{\textellipsis}

Fig.5. X-ray powder diffraction spectra with qualitative analysis of the major phases{\textellipsis}

Fig.6. Thermal gravimetric analysis (TGA) carried out on samples cured in the{\textellipsis}

}, issn = {00088846}, doi = {10.1016/j.cemconres.2014.08.008}, author = {Konrad J. Krakowiak and Jeffrey J. Thomas and Musso, Simone and James, Simon and Ange-Therese Akono and Franz-Josef Ulm} } @article {219, title = {Reactive elastomeric composites: When rubber meets cement}, journal = {Composites Science and Technology}, volume = {75}, year = {2013}, month = {Feb-11-2013}, pages = {77 - 83}, abstract = {

This paper describes a novel reactive composite material comprised of hydrogenated nitrile butadiene rubber (HNBR) compounded with slag cement. The composite initially looks and behaves like rubber, but when exposed to water it simultaneously swells and stiffens due to hydration of the cement component. The material eventually reaches a stiffness that is intermediate between that of HNBR and hydrated cement, while maintaining a relatively large ductility that is more characteristic of rubber. This behavior, which is ideal for sealing applications, differentiates this material from conventional swellable materials that become less stiff upon swelling. The development of this new type of material was motivated by the requirements of oilfield zonal isolation, where alternatives to cement are needed for some challenging sealing applications. A mechanism for the swelling and stiffening of the reactive composite is proposed: water diffuses into the HNBR matrix and is converted to bound water through hydration reactions with the cement, causing the effective solid filler content of the composite to increase. A model is proposed that treats the composite as a cellular solid with a continuous filler phase (hydrated cement). This model is able to reproduce the observed increase in the elastic modulus with time during exposure to water.

Elastic modulus ratio (current/initial) as a function of swelling, for HNBR ...

Kinetics of swelling of all three materials during approximately 1month of ...

Evolution of the elastic modulus of all three materials during approximately ...

Tensile stress{\textendash}strain curves for HNBR-cement (61{\textendash}39\% by volume, pre-exposure) ...

Schematic of the hydration process occurring inside the HNBR-cement material, ...

SEM images of HNBR-cement material before (left) and after (right) hydration. It ...

}, issn = {02663538}, doi = {10.1016/j.compscitech.2012.11.012}, author = {Robisson, Agathe and Sudeep Maheshwar and Musso, Simone and Jeffrey J. Thomas and Auzerais, Francois M. and Han, Dingzhi and Qu, Meng and Franz-Josef Ulm} } @conference {36, title = {Water Isotherms, Shrinkage and Creep of Cement Paste: Hypotheses, Models and Experiments}, booktitle = {Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete: A Tribute to Zdenek P. Ba{\.z}ant}, year = {2013}, month = {Sep-25-2013}, publisher = {ASCE Publications}, organization = {ASCE Publications}, abstract = {

Cement paste has a complex mesoscale structure, and small changes in its pore network potentially cause large variation in measurements such as the water isotherm (also nitrogen). We deconvolute the water isotherm with the help of advanced computational techniques, hypotheses, and a re-examination of published data. The pore system is divided into four different categories, each containing water with its own physical properties. By viewing the highly interdependent roles of water in each of the pore categories as a system, new insights are gained regarding possible mechanisms that control drying, shrinkage, and creep, and experimental strategies for verification.

}, doi = {10.1061/9780784413111.015}, author = {Hamlin M. Jennings and Enrico Masoero and Pinson, Matthew B and Strekalova, Elena G and Patrick A Bonnaud and Hegoi Manzano and Qing Ji and Jeffrey J. Thomas and Roland Jean-Marc Pellenq and Franz-Josef Ulm and others} }