FFC-NMR DISPERSION OF HYDRATED C3S: A MATLAB SCRIPT FOR THE PROFILE FITTING BY THE 3τau MODEL

Tricalcium silicate C3S is the major component in all kinds of cementitious materials, such as white or grey Portland cement. A deep understanding of its hydration process will enlighten us on the formation of the hydrates structure, like CSH. The use of Fast Field Cycling (FFC) is a good way to perform analyses on such kind of materials. In particular, FFC dispersion profiles of the longitudinal relaxation rates (R1=1)) on a wide range of NMR frequencies permit to get information on the dynamics of the diffusing spins, by analysing the acquired data with a suitable spin diffusion model. In this work, the 3τ model developed at the Physics Department, University of Surrey, has been fitted to experimental dispersion curve data. The model is mainly based on three characteristic correlation time constants: the bulk and the surface diffusion times and the surface desorption time. To easily fit this model to the dispersion profiles, a MATLAB® script code called 3τM has been created. The fitting process implemented in the script is based on the non linear least squares method, which will be shortly explained before a presentation of the 3τ model theory and its associated parameters. The material used, the fitting methods and the results will be also briefly described.