FAST IN-SITU X-RAY-DIFFRACTION STUDIES OF CHEMICAL-REACTIONS - A SYNCHROTRON VIEW OF THE HYDRATION OF TRICALCIUM ALUMINATE

We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy di spersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and thro ugh bulk samples, reveal an intermediate calcium aluminate hydrate app earing just prior to the formation of the final stable hydrate, demons trating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots fo r each phase over the whole hydration sequence. This improvement deriv es from being able to use smaller diffracting volumes and consequent r emoval of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution an d diversity of system.