Investigation of Permeability of Porous Natural and Engineered Building Materials

Most natural and engineered building materials such as sandstone and brick are porous, thus are subjected to moisture and contaminants possibly degrading them. Material permeability is expected to affect the contaminant transport into the material. This study investigated surface and macroscopic permeabilities of 20 building materials of varying porosities. The individual specimens were 7 cm in diameter and 5 cm in height. Permeabilities with gas and water as the pore fluid were determined. Surface gas permeability was determined using two devices, a hand-held device TinyPerm II, and fully automated laboratory device AutoScan II. The measurements were made on a grid pattern on one of the flat surfaces of the specimens.  In addition, macroscopic gas permeability and hydraulic conductivity with water as the pore fluid were determined using entire specimens. For the macroscopic gas permeability and hydraulic conductivity testing, procedures outlined in the American Society for Testing and Materials (ASTM) standards were followed. The TinyPerm II and AutoScan II techniques are new, and ASTM standards do not exist for these tests. Therefore, testing procedures provided by the Manufacturer were followed. For the results, measurements were used to establish expected correlations among different types of permeabilities (surface and macroscopic gas permeabilities and hydraulic conductivity) for each set of materials. Any influences of homogeneous versus heterogeneous and natural versus engineered were included to examine permeability affects on contaminant degradation. In conclusion, natural materials may have a specific range of permeability whereas man-made materials may possibly be designed to be more or less permeable.