Two important uses of refrigeration in large construction projects are the cooling of large masses of concrete, and the freezing of soil to facilitate excavation. During the hardening of concrete, its chemical reaction is exothermic, and if heat were not removed, the high temperatures would stress the concrete. Concrete may be cooled by chilling the sand, gravel, water, and cement before mixing, or by imbedding chilled-water pipes in the concrete. Another application of refrigeration is the freezing of wet soil in the vicinity of excavations to prevent cave-ins. The typically pipes are driven into the soil surrounding the area where excavation is to occur. Then cold brine circulates through the pipe coils and freezes the soil in its vicinity. When the frozen zones overlap, excavation can proceed.
Another special application of refrigeration related to construction is when a refrigeration plant maintains permafrost in its frozen state beneath a building or other facility in cold climates. If the heat from the structure were permitted to thaw the permafrost, the structure would sink. An example of this application is a hybrid thermosyphon serving a power plant in Gakona, Alaska. The permafrost is maintained frozen in winter by thermosyphon heat exchangers and in the summer by a mechanical refrigeration plant.