Laboratory study of a hydronic concrete deck heated externally in a controlled sub-freezing environment

Abstract

Geothermal heating of bridge decks is a reliable and sustainable method for bridge de-icing that has been increasing in demand since conventional de-icing methods were proved to be environmentally hazardous. Previous research on geothermal heating of bridge decks relied on hydronic pipes embedded inside of bridge decks, which are confined to newly constructed bridges. For existing bridges, a newly devised method for external heating has been recently tested under limited laboratory conditions to determine its overall performance. This study explores laboratory heating tests of a concrete slab with a thickness representing a typical concrete bridge deck. This slab was equipped with a simulated geothermal bridge de-icing system and tested inside a freezer subjected to sub-freezing controlled conditions. Various winter scenarios were applied to the system to determine its heating performance and how feasible it will be for the system to be transferred to the field. A prediction equation was developed to estimate the total energy reserves required to permit de-icing, and statistical analysis was performed and validated with test results. The slab surface heat flux was estimated to range from 27 W/m2K to 73 W/m2K from the heating test. The externally-heated deck can be designed with the developed prediction equation for snow melting.