Great work ! Judging from the pool plaster mix you used i wonder if you got that from my online concrete howto . just a few more tips for youYour concrete mix was excellent for maximum strength quite dry but this sucks for placement . You could have used a touch more water without compromising strength and it would aid in the placement and envelopment around your steel supports . Water reducer , either powder or liquid , would be ideal for improving placement viscocity with no loss to finished strength . I have done quite a few polished surfaces similar to yours . 3 days is enough for demolding but not enough to step sand yet . I wait a minimum of 2130 days before sanding otherwise the sand tends to break free from the mortar instead of polishing . If you wait a month before polishing you can make it shine like glass . Right before you place your mix in the form , use a watery mix of 1 part portland to one part sand and paint all of the corners and edges with this watery mix . This will help to get a smooth finish on these edges and avoid the pitting as you have . You can sack the edges with more plaster mix if you want to fix that detail . Overall great work !