Ant building a wood pile? Why? Ever seen this before?

I noticed yesterday (June 26) that there was a single ant collecting bits of wood and fluff and collecting them in the same spot on the brick pad in my backyard. I'm in Medicine Hat, Alberta, Canada.

I was able to look under the little pile today and then rebuild it, and noted that there seemed to be a hole down to under the bricks there, so that's being covered by this little guy. I was really happy to see it come back and continue work for a second day... well, I'm assuming it's the same ant.

I asked for an ID from some friends, and they think it's Formica Podzollica, but I'm not too concerned with the ID. I'm most interested in seeing if this is behaviour someone else has seen before.

Never seen an ant act like a beaver. It wasn't just piling the pieces up, it would bring thinner twigs back, have the end get caught on a larger object, drop the piece its carrying, move the larger piece it's getting caught on, go back to the first thick piece, insert it under the edge of the pile in the place seemed to want to before getting caught up, and then move the larger object back to where it was. I have a short video showing some of this. It gets lost a lot, but it's determined! If I didn't know better, I'd say he's building a lek like some dancing bird.

Ever seen anything like this before? Why would a single ant be working like this? Confused? Solo mission expanding the base? That's it's bedroom under there and it's too hot with the heat wave?

Imgur album (Red 4L milk jug lid for scale)

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