The pore system of sedimentary rocks as a key factor in the durability of building materials

We studied the pore system of six different types of sedimentary stone (two limestones, two sandstones, one dolostone and one travertine). Techniques based on the direct observation of the pore system (optical and scanning electron microscopes, digital image analysis) were combined with others used for indirect characterization (mercury intrusion porosimetry, N2 adsorption, hydric tests, and vapour permeability). In addition, we performed accelerated decay tests to determine the durability of the stones and to check the consistency of the results obtained in the pore system study. Digital image analysis allowed us to calculate the pore size distribution and the total porosity. Digital image analysis always gave higher values for total porosity than those determined by porosimetry and hydric tests, which only measure open porosity. The density values were congruent with the mineralogy of the stones. The stone that obtained the best results in the various tests in terms of its petrophysical parameters was dolostone, while the worst performance was by one of the two limestones. These results were confirmed by the decay tests. The combined use of these different techniques gave us an accurate interpretation of the pore systems of the six different stones, and also enabled us to correct misleading interpretations caused by the limitations of using one single technique. Our findings also provide useful information to help prevent the decay of these stones.