A study was made of the macrodefect-free (MDF) composite based on aluminate cement and a poly(vinyl alcohol)-poly(vinyl acetate) (PVAc) copolymer by C-13 cross-polarization magic-angle-spinning nuclear magnetic resonance. The spectra were run on both the copolymer and the MDF composite in order to observe the atomic environments of the carbon nuclei. An analysis of the intramolecular hydrogen bonds showed a stronger modification in the sample containing CaAl2O4 (CA) than in that containing Ca3Al2O6 (C(3)A). From the spectra, it was seen th at deacetylation had occurred, and that there was interaction between acetate groups and the calcium and aluminium ions. Proton relaxation times both in the laboratory frame, T-1(H), and in the rotating frame, T-1 rho(H), were exploited for the study of the dimension of the polymer matrix in MDF composites. An extended interphase was identified in the composite containing CA. A comparison with the behaviour of the composite based on silicates Ca3SiO5-PVAc high tig hts the better mixing of the phases in the MDF composites containing CA.