Experimental research on high-performance backfill materials for ground heat exchangers

Experimentally studies the influences of each component on the thermal conductivity, consistency, strength and expansion ratio of cement-quartz sand grout backfill materials. Recommends three high-performance grout materials with thermal conductivity of 2.18 to 2.34 W/(m·K). A case study shows that application of these cement-sand grout materials can reduce the buried pipe by 29% to 36% in length and the initial investment of ground heat exchangers and running energy consumption significantly compared with conventional bentonite grout.