While lunarcrete isn't airtight -- meaning living spaces would need sealing from the inside -- it's designed to absorb gamma rays, withstand huge temperature shifts (from −150 to 120 degrees Celcius!) and has a relatively light density of 2.6 grams per cubic centimeter. All these qualities, which are required by the lunar environment itself, also mean that lunarcrete -- or at least its simulated equivalent -- could have applications right here at home [source: Ruess et al].
Not only does lunarcrete involve transporting minimal materials (after the big first push, of course), but its ongoing manufacture also requires less energy than the production of steel, brick or aluminum. It will be at least a decade before we're able to see these materials and discoveries in action -- maybe more, depending on how we prioritize space programs in the years to come -- but in the end, lunarcrete is a smart and elegant solution to the problem of off-world construction.
The long-ago proponents of our space program knew that our discoveries on that journey would not only bring us to a new frontier, but would also generate jobs, discoveries and innovations for the planet we call home. After all, the beauty of experiments in the hard sciences is that every solution potentially begets a thousand others.