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The calcium aluminate hydrate AFm and AFt phases formed upon hydration of Portland cement have an important role in the stabilization and solidification of hazardous chromate ions in hardened cement. AFm monochromate (Ca₄[Al(OH)₆]₂(CrO₄)·12H₂O), AFm hemichromate (Ca₄[Al(OH)₆]₂(CrO₄)_0.5(OH)·12H₂O) and the chromate-containing AFt phase, Ca₆[Al(OH)₆]₂-(CrO₄)₃·24H₂O, were synthesized and investigated by ¹H, ²⁷Al, and ⁵³Cr MAS NMR spectroscopy. ²⁷Al quadrupolar coupling parameters (<i>C</i>_Q, <i>η</i>_Q) and isotropic chemical shifts (<i>δ</i>_iso) were determined for the three phases, including two distinct Al sites in chromate-AFt, as observed by ²⁷Al MAS and MQMAS NMR. Two dominant peaks are apparent in the ¹H MAS NMR spectra of each of the phases. For the AFm phases, these resonances are assigned to framework hydroxyl groups (1.7–2.0 ppm) and water molecules/hydroxyls (5.0–5.5 ppm) in the interlayer. For chromate-AFt, the peaks are ascribed to framework hydroxyl groups in the [Ca₆Al₂(OH)₁₂]⁶⁺ columns (~1.4 ppm) and water molecules (~4.8 ppm) associated with the Ca ions. ⁵³Cr MAS NMR spectra acquired at 22.3 T for the samples show a narrow resonance for both chromate AFm phases, whereas indications of three distinct Cr resonances are apparent for the chromate AFt. The absence of any second-order quadrupolar effects in the ⁵³Cr NMR spectra strongly suggests that the chromate ions are highly mobile in the anionic sites of the AFm and AFt structures. The NMR data reported in this work are in agreement with the reported crystal structures for the chromate AFm and AFt phases and may be useful for identification and characterization of chromate fixation in cementitious systems, complementing information gained from conventional powder X-ray diffraction studies.