Abstract: A method of measuring a strength of a capillary-porous chemically active material while hardening, the capillary-porous chemically active material including therein a liquid which undergoes metamorphosis and which is present in the capillary-porous chemically active material in different stages during curing, the method is effected by performing a high frequency, spin-echo nuclear magnetic resonance measurement of each stage of the liquid; and correlating the high frequency, spin-echo nuclear magnetic resonance measurement with a predetermined relationship between the strength and the high frequency, spin-echo nuclear magnetic resonance measurement.