All recommendations are welcome. In particular how to vibrate a two part mold without it breaking apart. I did not weigh the mix and water, but i suspect i used too much water. Also added about 2% plasticizer.
The next one did only get slightly better :( I vibrated it something like two minutes with the saw. Could it be bubbles forming from the mix? Maybe something about the plasticizer? Anyway i kinda don’t want to keep redoing this, i’m thinking about filling the holes and using it anyway, though it might crack due to freezing temperatures at some point i guess…
// Edit: specified that it was maybe slightly better