Abstract
Energy piles are used around the world to partially heat/cool buildings or de-ice pavements. Thermal conductivity of concrete is one of the key parameters which highly affects the thermal performance of energy geostructures. Application of higher thermally conductive concrete in energy piles helps to harvest more shallow geothermal energy. Besides, higher thermally conductive concrete results in more uniform temperature distribution and will significantly increase the efficiency of the geothermal bridge deck de-icing. It is expected that the thermal conductivity of the concrete depends on its age and the applied curing conditions. The thermal conductivity of concrete can progress with the progression of hydration. While the hydration process is highly dependent on the curing condition that is applied. In this study, several concrete samples are prepared and cured under different conditions (inside the humidity room, indoor, and outdoor). Then the thermal conductivity of concrete samples at different ages are measured according to ASTM D5470-17. Results show an increase in thermal conductivity of concrete cured in humidity room for the first 30 to 40 days that thermal conductivity were measured In addition comparison of thermal conductivity of the outdoor and indoor samples show the importance of the ambient temperature and relative humidity on the thermal conductivity value.
Highlights
Thermal conductivity of concrete is an important parameter in energy pile design
While it has been found in literature that age has limited effect on the thermal conductivity of concrete [5], the results showed hydration process in the first 28 days might affect the thermal conductivity value especially for samples placed inside the humidity room
Thermal conductivity of the samples could not be measured at the same day since thermal conductivity test for each test could take up to 10 to 15 hours in order to make sure temperature at the top and bottom of the concrete samples reach to the steady state condition
Summary
Thermal conductivity of concrete is an important parameter in energy pile design. Higher thermal conductive concrete helps to harvest more geothermal energy through geothermal piles and increases the efficiency of the geothermal bridge deck de-icing. Thermal conductivity (k) of concrete is greatly affected by mix proportions, aggregate types, sources and sizes, moisture content and unit weight [1,2,3]. Thermal conductivity of concrete can be influenced by the pore distribution and entrained air volume in the mix design. Pore distribution analysis using x-ray tomography demonstrated that, air entrainment can be used as a sealer for thermal insulation [4]. A separate study was conducted to determine how k value changes with variables such as admixture type and content (like fly ash and slag), coarse and fine aggregate type and content, age, temperature, water-to-cement ratio, and
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
