Permeability Studies of Reinforced Thin-Shell Concrete

摘要

Falling-head permeability tests were conducted on specimens of two normal-weight concretes and two lightweight concretes typical of those used in thin-shell reinforced concrete roofs. Specimens of each concrete with galvanized mesh reinforcement were tested in thicknesses of 1 inch, 2 inches, and 4 inches. Initially, the upper face of each specimen was exposed to a 20-inch head of water. The lower faces of the specimens were initially exposed to relative humidities of 25%, 50%, 70%, or 100%, all at a constant temperature of 73.4F. A lightweight concrete utilizing expanded shale for both coarse and fine aggregate was the least permeable of all the concretes tested. The degree of zinc oxidation from the mesh was determined for some of the specimens. The reliability of the equation for coefficient of permeability (falling head) could not be verified. Any of the concretes tested in this study could be used to make a relatively impermeable thin-shell concrete roof. Since the concrete itself can be made satisfactorily resistant to water passage, cracks are the most significant source of water leakage through thin-shell concrete roofs. (Author)