Hydration behaviour of simulated high-performance concrete pastes using synchrotron energy-dispersive diffraction

Synchrotron radiation energy-dispersive diffraction has been used for the first time to evaluate the hydration behaviour of simulated high-performance concrete (hpc) pastes. The hydration of the alite and ferrite and formation of Ca(OH)₂ were monitored as a function of the initial H₂O content. A significant and stable ettringite (AFt) content was found in all pastes, perhaps close to 6·5% in certain mixes. The morphology of AFt depended on the initial mix design. Monosulphate (AFm) was detected, the amount present increasing with increasing initial H₂O content. The technique has the advantage of monitoring the overall hydration behaviour of the paste while it is still ‘wet’. By such an approach the less stable phases such as AFt and AFm can be detected and characterized. These are of potential importance in relation to the long-term durability of hpc.