Laboratory Evaluation of Nondestructive Methods to Measure Moisture in Built-Up Roofing Systems

摘要

This laboratory study investigated the reliability and accuracy of three types of nondestructive evaluation (NDE) methods to quantitatively determine the moisture content of the insulation in built-up roofing specimens. These methods were electrical capacitance, nuclear backscatter, and infrared thermography. Thirty-six roofing specimens, which consisted of five types of rigid-board roof insulations, with attached bituminous built-up membranes were tested over both concrete and steel decks. A wide range of moisture contents was induced into the specimens by maintaining a constant water vapor pressure difference across them. Two performance characteristics of the NDE methods were evaluated: (a) the minimum moisture content a method could detect, and (b) the relationship between NDE response and moisture content beyond the minimum detectable moisture content. The two performance characteristics were assessed through normalization parameters defined in terms of the NDE response and its scatter about a fitted curve. There were differences in the performance characteristics, the magnitude of which depended on the NDE method, the specimen composition, and the deck type used.