Well, this is handy. I may learn something on cinder blocks. I'm not sure if I have a cinder block correct. Apologies if not.
I've put a link below to describe what I mean. Like the centre pic on the left in the link but holes were a little larger (or same size and crays were smaller than I remember). Blocks were grey colour so I'm assuming concrete. How they were made I don't know.
As well as this there were other coloured bricks. Grey bricks were rougher, I didn't like using them.
It was basically anything I could find but I can't remember where I got the bricks from. House had been built around 4 years previously so may have been spare bricks stored in garage.
Now I'm kind of wondering on leached metals or chemicals. The only thing that may have saved me was every filter had carbon in it.
Anyways if I did this again, I assume all concrete made stuff has to cure? How long does it take and do you just know from ph stabilising?
Any risk with other chemicals leaching? Also I would go around the building sites or hardware - are all concrete made products the same problem? Thanks in advance.