Probing the hydration of composite cement pastes containing fly ash and silica fume by proton NMR spin-lattice relaxation

Proton NMR spin-lattice relaxation (T1) was used as a prober for observing the hydration process of composite cement pastes blending fly ash and silica fume during the early age. The distribution at initial time, evolution curves and signals intensity of T1 were shown in this paper. Results demonstrate that the T1 distribution curves at initial time exhibit two peaks, which are regarded as two different water phases in the pastes. The evolution curves of T1 are in good agreement with the hydration process of composite pastes and could be roughly divided into four stages: initial period, dormant period, acceleration period and steady period. The hydration mechanism for each stage was discussed. The hydration of the composite cement pastes was retarded by the addition of fly ash and silica fume when compared to that of pure cement. However, the hydration degree of the cement in the blends was promoted.