A study of several chemical and electrochemical factors which affect the behaviour of embedded steel in cement pastes and concrete has been made. The effects of internal and external sources of chloride ions on the pore solution chemistry of Portland cement pastes, with and without additions of anodic corrosion inhibitors, have been studied using a pore solution expression device which has enabled samples of pore solution to be expressed from hardened cement pastes and analysed for various ionic species. Samples of pure alite and tricalcium aluminate have been prepared and characterised with respect to morphology, free lime content and fineness. Kinetics of diffusion of chloride ions in hardened pastes of alite and alite blended with tricalcium aluminate have been investigated and an activation energy obtained for the diffusion process in alite. The pore structures of the hardened pastes and the chloride ion binding capacity of alite have also been determined. Concrete cylinders containing embedded steel with four different surface conditions were exposed to various environments. The electrochemical behaviour of the steel was monitored during the period of exposure by means of rest potential measurements and the steel corrosion products analysed before and after being embedded. An examination was made of the nature of the interfacial zones produced between the embedded steel and cement. Rest potential measurements were monitored for steel embedded in alite paste in the presence of chloride ions and cement paste containing various levels of inhibitors in combination with chloride ions. In the latter case the results were supported by polarisation resistance determinations.

The presence of a distinct compound in the Pt-Fe Cu system at Pt FeCu composition was hypothesised by Nemilov in 1944, but tre compound (Tulameenite) was first identified by Cabri et al in natural alloys from the platinum placer deposits of the Tulameen river in British Columbia. The present research was initiated to determine the Pt-Fe-Cu phase diagram in the Pt FeCu region and thus to determine the composition range of Tulameenite and its compositional and structural changes during different thermal treatments using synthetic material. Primary investigations have revealed that the compound is a single phase disordered f.c.c. solid-solution above 1178°c. On quenching, it transforms, probably by a martensitic transformation, to an ordered tetragonal structure. Multiple twinning on {101} habit planes avoids any macroscopic shape change due to the ordering. The twinned structure is unstable, and thermal treatments produce stress-relief recrystallization accompanied by deformation twins and grain-boundary fractures as further stress-relief mechanisms. Tulameenite forms an extensive single phase region of solid- solution continuous with the binary region based on the compound FePt. At lower temperatures the stoichiometric compound Pt2 FeCu enters a two-phase field comprising a non­- stoichiometric compound together with an ordered cubic phase. The transformation to this two-phase structure occurs by different precipitation mechanisms which are accompanied by recrystallization of the matrlx in some cases.