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Abstract
The properties of coal-tar pitch roofing membranes approximately 21 years old were compared to the properties of new membranes and the suggested level of performance for such membranes reported previously by the NBS. Samples of old membranes were taken from eight buildings having roof areas that ranged from 0.5 to 1.5 million square feet. The buildings were located at three sites in or near the state of Kentucky. The roof membrane on these buildings had been subjected to different maintenance procedures. Laboratory tests conducted on 47 membrane samples included tensile strength, load-strain determination and coefficient of thermal expansion. The thermal shock factor was calculated for each sample. Laboratory observations were made to determine between-ply bitumen thickness, weight per unit area, ply adhesion, pliability and condition of the membrane. The tensile strength of the old membranes determined at O degrees F (-18 C) in their longitudinal and transverse directions and values of the coefficient of thermal expansion measured over the temperature range of 0F to -30F were comparable to those values reported earlier by NBS. The moduli of elongation were considerably higher for the old membranes than for the new ones, which resulted in lower values of thermal shock factor. The lower values of extensibility (higher moduli of elongation) of the old membranes were attributed to their brittleness caused by aging. Differences in roof maintenance procedures appeared to have caused significant differences in the properties of membranes from the three different sites.
The properties of coal-tar pitch roofing membranes approximately 21 years old were compared to the properties of new membranes and the suggested level of performance for such membranes reported previously by the NBS. Samples of old membranes were taken from eight buildings having roof areas that ranged from 0.5 to 1.5 million square feet. The buildings were located at three sites in or near the state of Kentucky. The roof membrane on these buildings had been subjected to different maintenance procedures. Laboratory tests conducted on 47 membrane samples included tensile strength, load-strain determination and coefficient of thermal expansion. The thermal shock factor was calculated for each sample. Laboratory observations were made to determine between-ply bitumen thickness, weight per unit area, ply adhesion, pliability and condition of the membrane. The tensile strength of the old membranes determined at O degrees F (-18 C) in their longitudinal and transverse directions and values of the coefficient of thermal expansion measured over the temperature range of 0F to -30F were comparable to those values reported earlier by NBS. The moduli of elongation were considerably higher for the old membranes than for the new ones, which resulted in lower values of thermal shock factor. The lower values of extensibility (higher moduli of elongation) of the old membranes were attributed to their brittleness caused by aging. Differences in roof maintenance procedures appeared to have caused significant differences in the properties of membranes from the three different sites.
Date
6/1977
6/1977
Author(s)
Walter Rossiter Jr; Robert Mathey
Walter Rossiter Jr; Robert Mathey
Page(s)
22
22
Keyword(s)
bituminous roof; coal tar pitch; performance criteria; physical property; engineering property; test method
bituminous roof; coal tar pitch; performance criteria; physical property; engineering property; test method