In situ 27Al NMR studies of cement hydration

Hydration of calcium aluminate cements is known to cause phase transformations during which the coordination number of aluminum by oxygen changes from 4 to 6. Systematic 27Al magic angle spinning and wide-line nuclear magnetic resonance (NMR) experiments at 78.3 MHz with detailed attention to the quantitative aspects of quadrupolar NMR spectroscopy show that the fraction of Al(6) is a monotonic function of the water/solid (w/s) ratio and does not depend on the type and concentration of setting accelerators. in situ 27Al wide-line NMR measurements during the hydration process can provide good estimates of the induction period and the rate of the phase conversion. Using this approach, lithium carbonate at a concentration of 0..5 wt% of the mixing solution has been shown to eliminate the induction period but to leave the rate of the phase conversion essentially unchanged