Investigation of the structure of ettringite by time-of-flight neutron powder diffraction techniques

The crystalline structure of ettringite, Ca6[Al(OH)6]2(SO4)3·∼26H2O, was investigated using high-resolution time-of-flight neutron powder diffraction techniques. The powder diffraction data were subjected to Rietveld crystal structure refinement. The resultant ettringite crystal structure confirmed the positions of Ca, Al, and S atoms while permitting a more precise determination of the locations of O and H atomic positions than in previous X-ray and neutron diffraction studies. A discussion of the ettringite hydrogen bonding network is presented, illustrating the role of hydrogen bonding in the stabilization of the ettringite structure.