In summer 2020, I wrote an article for The Driller titled “Water and Graphite: A Geothermal Game Changer.” In that article, I discussed the effects on geothermal mixes utilizing graphite vs. sand. Here is an excerpt from that article to refresh the reader’s mind:
Manufacturers of geothermal grouts found out early that graphite is a “big lever” in a geothermal mix. This means that only a small amount of graphite increases the TC value dramatically. The amount of water in the mix directly affects the swing of the graphite lever — that is, the thermal conductivity — in an unexpectedly large way. In a typical graphite-containing mix, increasing the water by 1 gallon will see a reduction of thermal conductivity of up to 15%. That means if you are supposed to be adding 15 gallons of water to your mix and the actual amount is 16-gallons, an expected 1.2 TC value may test at 1.02 TC. Likewise, decreasing water by 1 gallon will send TC values the opposite way.