Evaluation of stone pore size distribution by means of NMR (original) (raw)

Proceedings of the 9th International Congress on Deterioration and Conservation of Stone, 2000

Abstract

Publisher Summary Nuclear magnetic resonance (NMR) is a technique that exploits magnetic properties of atomic nuclei with spin quantum number different from zero in an external magnetic field. The energy exchanges between the system and its surroundings is obtained by studying the time length needed for the spin system magnetization to reach the equilibrium value, after a selected perturbation. Therefore, NMR helps in determining the interactions between the pore walls and the hydrogen nuclei of water molecules trapped in the stone porous structure. This further gives information about the chemical-physical properties of the porous matrix. The determination of porous matrix properties in natural porous stones is a very important goal in the Cultural Heritage conservation field. Porous structure of a natural stone depends on its genesis and on its particular history. This chapter describes the application of nondestructive NMR technique to determine pore size distribution function on samples of Carrara marble, Candoglia marble, and travertine. The experiment conducted compares the experimental relaxation data with the data obtained from a simulated porous system. Two marbles and one limestone are compared with samples treated with three different agents: (1) a consolidating, adhesive and binding agent; (2) a hydrophobic protective and preconsolidating agent; and (3) a hydrophobic protective no-film agent. NMR data based analysis is totally non-destructive and is representative of the critical regions where water can be dangerous. It provides useful analysis of the material conservation degree and a pointed conservative treatment. The chapter also provides tables and graphs to illustrate mean values and standard deviations of pore size distribution function in different samples.

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