This article presents the results of the study of changes in the properties of porous ceramics and concrete under the influence of “freeze—thaw cycles” produced by employment of nuclear magnetic relaxation. The measurements of nuclear magnetic relaxation times T1 and T2 were performed on saturated water samples with 60 cycles of freezing using spin echo methods “CPMG” (T2) and “inversion — recovery of the equilibrium of nuclear magnetization” (T1). The results are interpreted assuming the two-exponential dependence of the magnetization on the time in the process of establishing equilibrium. A relation between periodic temperature effects and the change in the number of pores and their connectivity was found. To confirm the assumption of the absence of the effect of the paramagnetic ions on the relaxation process, an experiment with samples saturated with heavy water was carried out. Refs 9. Figs 8. Tables 2.