I gave the underground bunker plans to Claude and asked it to estimate the concreted used in various portions of the house. Here are its estimates:

Roughly 775,000 lb of concrete (about 390 tons) in the whole structure. That splits into about 370,000 lb in the shell, 300,000 lb in the floor and footings, and 110,000 lb in the retaining walls. These are estimates measured from the plans and the retaining wall table, not as-built figures.

Since I’m talking about the concrete, I might as well report on the compressive strength of the shell concrete. The plans called for 4,000 PSI. The shotcrete guy asked the concrete supplier for 5,000 PSI. The supplier mixed it a little stronger to make sure he met the requirement. The sample I took in for testing tested as:

Results (28 days, cored 10/17/23, tested 10/19/23, placed 9/21/23):

Core	Load (lbs)	Strength (psi)
1	15,460	5,153
2	16,510	5,503
3	15,860	5,287
Average		5,314

133% of required. I paid for a lot more than what I really needed. <heavy sigh>

I rationalize it by telling myself that had it come in under the specified numbers it was not like it could be easily torn out and redone. The forms and rebar alone took a crew of three to five several weeks to build. So, better safely overbuilt than being forever concerned about it caving in.