I have a lot of specifications stuck in my head from previous jobs. A fun one is that precast concrete bridge beams aren’t just concrete and rebar. They typically have a bunch (20-30 or more depending on size) of 13 mm steel cables that are each under about 13,000 kg of tension. The cables are pulled to a specific tension in the concrete form, the concrete is poured around them, then the cables are cut at each end.