Validation of cylindrical pavement specimen thermal conductivity protocol

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Bai, Haotian
Iowa State University
Filler materials; Pavement thermal conductivity measurement
thesis / dissertation description
Pavement thermal property plays a vital role in forming Urban Heat Island effect that influences the comfort level and the environment. While other pavement properties are relatively easy to acquire using field instruments, thermal conductivity needs to be obtained using laboratory measurements. A method to measure the thermal conductivity was developed by Arizona State University (ASU). In this study, this method which utilizes cylindrical specimen geometry was validated for its feasibility and accuracy. However, the effectiveness of the thermal interface filler materials used to fill the air gap between the heat source and testing pavement materials has not been thoroughly evaluated. Four different types of filler materials were selected and evaluated: high pressure lithium grease, Moly-lithium grease, petroleum jelly, and Omega paste. The test results indicate that Omega paste, a silicone-based thermal grease commonly used in electronic devices, gave the highest thermal conductivity of the asphalt and concrete samples tested. This is due to its higher thermal conductivity (2.3 W/m-K) as compared to the other three filler materials tested even though the workability of Omega paste was not as good as the other three. The Omega paste was confirmed as a suitable filler by conducting tests on a material with a known thermal conductivity. For the ASU method to be accurate, the thermal conductivity of the selected filler material needs to be higher than the top and bottom insulation of the test piece, due to the one-dimensional steady-state heat flow in the test piece.