That is unusual, once going through the bottle shaker should actually be done... but as far as the mixing ratio is concerned, I wouldn’t worry too much, it was properly reinforced.
What exactly is a "Baufachmann"? If the concrete hasn't properly set, you'll definitely notice because it becomes porous. However, I don't assume that's the case. The lack of compaction, on the other hand, is quite annoying. Recently, we built a small garden wall foundation, and we were able to press everything together quite well with just a wooden board attached to a handle. With proper equipment, more could have been done. Definitely do that with the stones.
then we have used exactly 8 tons of gravel and 1.250 tons of cement. With a ratio of 1:4, it should have been 2 tons of cement.
Hello Eriwan
a ratio of 1:4 would have been reasonable for concrete. I even tend to 1:3 for something like that. You now have about 1:5. That is "lean concrete". 20cm with proper rebar inside. Nothing will happen there. Provided the concrete was well moist so it compacted. Then the rebar won't rust. What should happen to the base slab? It can neither move sideways nor downward. And neither bending nor tensile forces act on it. Don't worry about that. Connection rebar is good. Also put horizontal and vertical rebar into the formwork blocks. Use a mixture of 3.5:1. So, when mixing, 3 and a half shovels of gravel, 1 shovel of cement. Approximately. Make it well moist. The stuff has to flow like batter. Tamp a bit with a roof batten and your pool will be fine.
Yes, and that is confusing for me because: the information actually refers to the weight. So 1:4 means 1kg cement to 4 kg gravel. But gravel is significantly heavier than cement, so the number of shovels cannot work. 1:4 would be more like 2 shovels of cement to 4 of gravel, right? So I have 1:6.25 (estimated).
My goodness, don’t make a science out of it. If you have properly compacted underneath, nothing will happen there. If you are unsure, then take it out and do it again once.