Multiscale porosimetric description of pore network in building stones

As is well known, porosity strong affects physical and mechanical behavior of stones. In addition, being able to vehicle moisture, porosity has a great influence on durability. Therefore, the complete knowledge of the pore architecture and the behavior of stones interested by weathering processes represents a key element in understanding mechanism of degradation and prevent damage [1-2]. Pore network of stone is traditionally investigated by porosimetric techniques based on gas adsorption and mercury intrusion. Nevertheless, these methods appear inadequate for the complete modeling of the microstructure of the rock, since they are destructive, measure only the open porosity and explore a limited dimensional range. Moreover, most of these techniques, are based on assumptions about pores shape and dimension, representing an ideal geometric model of them [2]. As aforementioned, the quantitative description of stones pore network cannot be generally achieved by a single technique, considering the real complex geometry and the variability in the dimensional distribution of voids [3]. In recent years, the use of nuclear magnetic resonance (NMR) as useful tool for studying pore structure in stones has largely increased, also in association with other methodologies [5-7]. In detail, the technique allows to get information about the pore size distribution in a water-saturated rock by measuring the transverse and longitudinal relaxation times of water hydrogen nuclei in a non destructive and non invasive way. Furthermore the investigation of water diffusion through the porous structure provides information on the restricted geometry of the network and the obtainment of the average pores radius and pores interconnection. The main goal of this study is to compare portable NMR and mercury intrusion porosimetry in characterizing pore size distributions of building stones and quantify pore network modification due to salt weathering. In detail, this methodological approach has been applied on a coarse grained calcarenite from Sabucina (Caltanissetta, Sicily, Italy) widely used as building and replace stone. The obtained data allow to highlight potential and limitation of the applied analytical methodologies in studying building stone materials. [1] D. Benavente, M.A. García del Cura, R. Fort, S. Ordóñez, Engineering Geology 74, 2004, 113–127. [2] S. Yu, C. T. Oguchi, Engineering Geology 115, 2010, 226–236. [3] C. A. León y León, Advances in Colloid and Interface Science 76-77, 1998, 341-372. [4] G. Barbera, G. Barone, V. Crupi, F. Longo, G. Maisano, D. Majolino, P. Mazzoleni, S. Raneri, J. Teixeira, V. [5]Venuti, European Journal of Mineralogy 26(1), 2014, 189 – 198. [6]V. Di Tullio, M. Cocca, R. Avolio, G. Gentile, N. Proietti, P. Ragni, M. E. Errico, D. Capitani, M. Avella Magnetic Resonance in Chemistry, 53, 2015, 64-77. [7] G. P. Matthews, C. F. Canonville, A. K. Moss, Physical Review E 73, 2006, 031307. G.S. Padhy, C. Lemaire, E.S. Amirtharaj, M.A. Ioannidis, Colloids and Surfaces A: Physicochem. Eng. Aspects 300, 2007, 222–234