a b s t r a c tThe tribocorrosion behaviour of a 304L stainless steel/alumina contact was investigated in sulphuric acid at two imposed potentials (cathodic and passive). The metal deformation below the surface was investigated by analyzing cross sections using secondary electron microscopy (SEM) and electron back scatter diffraction (EBSD). Cross sections were also prepared using focussed ion beam (FIB) and analyzed by in situ SEM. AES depth profiling was used to analyze surface composition. Metal subsurface deformation resulted in the build up of a deformed layer of approximately 20 m thickness in the near surface zone within the wear track. This layer exhibited a deformation gradient with high deformation close to the surface resulting in grain refinement down to 10 nm. The applied potential influenced the deformation: at passive applied potential more strain was accumulated below the surface resulting in more pronounced grain refinement and higher density of defects. Using AES analysis no alumina transfer from the counter body or any significant burying of oxide below the surface could be detected.

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The main product of Portland cement hydration is C-S-H. Despite constituting more than half of the volume of hydrated pastes and having an important role in strength development, very little is known about the factors that determine its morphology. To investigate the relationship between the chemical composition, silicate anion structure and morphology of C-S-H, samples were synthesised via silica-lime reactions and by the hydration of C 3 S under controlled lime concentrations and with/without accelerators. The silicate anion structure of the samples was studied by A relationship between the silicate anion structure and the morphology of C-S-H was found for the samples fabricated with accelerators.

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The use of supplementary cementitious materials as a partial replacement for Portland cement is the most effective way to reduce the carbon footprint of the concrete industry. Raw clays containing kaolinite (kaolin) are promising substitute materials. In the field, raw clays are often mixed with calcite and this is thought to affect their behaviour after calcination. This study explores the influence of calcite impurities on the mineralogy and reactivity a kaolinitic clay. A kaolin sample was blended with different quantities of calcite. The results show that during calcination calcite is decomposed, but no significant amount of free lime or amorphous calcium carbonate are formed. A granular deposit was observed that partially covers the kaolinite particles. The decomposition of calcite and formation of the deposit is associated with a reduction in specific surface area, which increases with the amount of calcite that is intermixed in the raw clay. TEM-EDS analysis showed that the deposit corresponds to a new phase formed from the interaction of kaolinite and calcite, with an Al/Si ratio ranging from 0.74 to 0.88 and Ca/Si ratio between 0.86 and 1.65. Reduction of the calcination temperature to 700 °C reduces the calcite decomposition and the negative impact on reactivity.

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