The hardening of Portland cement observed by 1H spin-lattice relaxation and single-point imaging

The nature of hydration in ordinary Portland cement samples from different Polish factories was investigated by the proton spin-lattice relaxation time T-1 and single-point imaging (SPI). The time dependence of the spin-lattice relaxation time T-1 shows the usual behavior: T-1 is constant at the beginning of hydration (the dormant period), then, during the setting process, decreases to the constant value in the hardening period of hydration. However, there are some anomalies in T-1 connected with the different amount of the mineral components in the cement sample. The unusual behavior of the stretched parameter alpha, after about 20 h of hydration, is observed and connected with the microcracking of the cement matrix. The 1-D and 2-D SPI images of the cement paste taken at various times of hydration show the distribution of the water throughout the sample and clearly demonstrate the usefulness of SPI in the study of the internal structure of the porous system.