Well good for you. We don´t have a crucible yet on day 24. I started building that big hordebase to use after our initial one on day 12 already even though we won´t need it before day 28. No steel that early and upgrading gives you XP. A lot of them. Also you get a lot of stone anyways when mining and afaik steel blocks do take ages to craft, so i rather upgrade instead.
And in SP you can go with concrete for a long time. You actually only really need steel once the demolishers show up wich is usually on day 49 or 56 and even then you can go without steel if you aim carefully and have more than one path to your position.