Potential Applications of Electrically Conductive Concrete

<b>Research Summary </b><br/>Following in the footsteps of many^1,2,3, our objective was to investigate whether electrically conductive concrete could be used to de-ice roads⁴, regulate surface temperature, or convert heat to energy in hot environments. Several 5cm³ (2in³) samples with embedded electrodes were fabricated. Concrete formulas containing conductive materials such as carbon fibers, iron powder, and steel wool were prepared ^5,6,7. Preliminary results indicate this technology has the potential to reduce the use of environmentally harmful chemicals, provide control surface temperature and produce energy in hot climates.<br/><b>Electrically Conductive Concrete </b><br/>Using a 12v DC power source and multimeter, current was measured between electrodes. Compressive strength was tested using a Rebound Hammer. Two concrete batches were prepared with 5% or 15% conductive material by volume. 5% Iron Powder and 15% Steel Wool were the most electrically efficient. The 15% Iron Powder samples lost compressive strength, shattered and were eliminated. The current was applied to all of the samples for two hours. Temperature was read using a commercially available infrared thermometer. The Iron Powder and Steel Wool samples averaged a 7° increase in temperature above room temperature.<br/><b>Regulating Temperatures </b><br/>Phase-changing materials (PCM) absorb or releases energy ^8,9. To investigate the rate of temperature change in concrete we cut paraffin wax, the PCM, into 1cm³ cubes and added them to the concrete mixtures. We constructed a test chamber with electric heaters to heat our samples to approximately 180°. The initial temperature of the cured samples was ~73°. After 10 minutes the temperature of control samples rose 58° to 131°. The PCM concrete’s temperature rose only 34° to 107°. From 10 to 30 minutes, the temperature of both samples rose at the same rate. After 40 minutes, the rate of change slowed and at 50 minutes all samples reached a constant temperature, around 185°. The temperature increase was delayed during the initial heating, presumably during the time the paraffin was absorbing the heat energy.<br/><b>Thermal Energy </b><br/>Seebeck, Peltier, and others developed thermoelectric generators to convert heat to electricity. ^10,11,12. To use the Seebeck Effect, we used 5% steel wool concrete, electric heaters, Sterno™, Peltier tiles, and a 40° ice-water bath. We heated 5cm³ blocks indoors using electric heaters to 160° and outdoors using Sterno™ to 240°. After 80 minutes the heated concrete samples were placed on a Peltier tile attached to a multimeter, placed in a 5 mil aluminum cup and lowered into the bath. With the temperature difference of 120° between the indoor sample (160°) and the water, 1 volt was generated with a decay rate of -0.001 volts per 30 seconds. For the outdoor sample (240°) 1.3 volts were generated with the same decay rate.<br/><b>Conclusion</b><br/>In an era of concern for climate change and global warming we believe the formulation of concrete can be modified using inexpensive materials to reduce the use of harmful chemicals, change the rate at which pavement temperatures change, and collect solar radiation to generate electricity. The authors would like to thank Malden Catholic High School for their support on this project.<br/><b>References </b><br/>1 Gagg, Colin R. doi:10.1016/j.engfailanal.2014.02.004,<br/>2 climate.mit.edu/explainers/concrete Accessed 7-10-2023<br/>3 M. Steinberg et al., BLN 50134 (T-509), 1968<br/>4 Dina, A et al https://csce.ca/Paper_MA9_0610035034.pdf<br/>5 Lai, Yet al atlantis-press.com/proceedings/ame-16/25857988<br/>6 Logan, A. (2021, April 20). news.mit.edu<br/>7 Wang, D. et al Science Direct.abs/pii/B9780128189610000259<br/>8 Chandler, D. L. (2017, November 16). news.mit.edu<br/><i>9 Phase-change material</i>. en.wikipedia.org/wiki/Phase-change material.<br/>10 Thermophile. en.wikipedia.org/wiki/Thermopile<br/>11 Chu, J. (2018, Jan 16). news.mit.edu<br/><i>12 Thermoelectric generator</i>. en.wikipedia.org/wiki/Thermoelectric generator