The Ingredients of Lunarcrete
Lunarcrete was first proposed in 1985, by the University of Pittsburgh's Larry Beyer. Sometimes called "mooncrete," its basic ingredients aren't much different from what we use in Earth-bound concrete: a solvent, the crushed-up aggregate and the sticky cement. The question, then, is what can be used for those three ingredients, since it's cost-prohibitive to transport them to the lunar surface?
The bulky part of concrete, the aggregate, can be made of the top layer of lunar soil, called "regolith." It's similar to what we use on Earth, although unlike our soil, it doesn't contain anything organic. The moon's regolith layer was created over billions of years by meteoroids of all sizes bombarding the surface, and sometimes crushing what was already there.
About 4 to 6 meters (13 to 20 feet) under the regolith, you find regular moon rock, similar to our bedrock layer [source: Wilcox, et al]. We can use high-calcium deposits here for the cementing part of the mix. But what about the solvent? The moon is a pretty dry place.