@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} }