What about water ice as a building material?

It's the same physics as the current Odyssey search for water. It hould provide a near ideal shield for charged particles of a solar origin. Cosmic Rays (extremely high energy nuclei from points beyond) would probably only be marginally affected but what can you do? Even on Earth, 2 go through your head every second.

Now, even in .167g, I'd personally be a little nervous with ice as the main structural component, but what about a kind of tiled coating.

Picture a geodesic or lower (geometric) profile tiled dome structure made of something like aluminum. Then a complimentary cover of tiled ice plates covering the dome structure.

In the direct sunlight, the ice would just begin subliming as the sunlight heating removes the rad shield one monolayer at a time. But cover it with a sheet of metalized mylar to reflect the sunlight and it would probably last forever.

Some things...

-The ice would also act as a kind of ablative armor for micrometeorite impacts and the plates could be easily replaced or anealed.

-No heavy dirt moving equipment is required to escavate then cover a
dome.

-All materials mentioned here could be obtained in-situ on the moon, assuming the infrastructure to process them.

-A specialized process to make and anneal the ice plates, which is not hard to picture after making ice cubes my whole life....

Now sharks, the chum is in the water. Eat it if you can......