Air permeability assessment of corrugated fiber-cement roofing sheets

摘要

The air permeability of full-sized commercial corrugated fiber-cement roofing sheets was assessed by two non-destructive experimental methods. Unlike the technical standards that recommend only visual verification of water impermeability or the laboratory tests that rely on the extraction of samples for airflow analysis, the methods described in this work allowed to obtain permeability parameters of crests and troughs everywhere in the sheet without damage. The permeability coefficients, retrieved from Forchheimer's equation, varied two orders of magnitude for k(1) (4.65 x 10(-17) m(2)-2.94 x 10(-1) m(2)) and almost 6 orders of magnitude for k(2) (7.02 x 10(-16) m-1.07 x 10(-10) m) along lateral and longitudinal positions in the sheet. Crests were more permeable for downward flow while troughs were more permeable for upward flow. The flow anisotropy was related to the peculiarities of the Hatschek process. The pressure-decay technique allowed a much faster data acquisition compared to the conventional steady-state permeametry.