Effects of hydrophobic treatments of stone on pore water studied by continuous distribution analysis of NMR relaxation times

The effects of protective hydrophobic products applied to porous media such as stone or mortar vary greatly with the product, the porous medium, and t he mode of application. Nuclear Magnetic Resonance (NMR) measurements on fl uids in the pore spaces of both treated and untreated samples can give info rmation on the contact of the fluid with the internal surfaces, which is af fected by all the above factors. Continuous distributions of relaxation tim es T-1 and T-2 of water in the pores of both synthetic and natural porous m edia were obtained before and after hydrophobic treatment. The synthetic po rous media are ceramic filter materials characterized by narrow distributio ns of pore dimensions and show that the treatment does not produce large ch anges in the relaxation times of the water. For three travertine samples mo st of a long relaxation time component, presumably from the largest pores, remains after treatment, while the amplitude of an intermediate component i s greatly reduced. For three pudding-stone samples, treatment leads to a su bstantial loss from the long component and an even greater loss from the in termediate component. (C) 2001 Elsevier Science Inc. All rights reserved.