I started to make a new fence and dug 30inch deep holes and filled them with cement. I have a metal anchor sticking out of the ground attached to the cement that will hold the 4x4s with big bolts.
The problem is that the posts are now attached and it rained the night the cement went in. Now the cement is a little loose like they are sitting in holes that are little to big and loose. The gound is mostly sand below 12 inches.
What can I do. I was thinking of digging around the cement and adding more to make a bigger base for the posts to sit on.
three quarter inch minus crushed rock tamped ,poked or compacted in around the sides. seeing that you have sand around it, digging the hole larger might just be as loose. what you need to do is compact the soil with the rock around the post. test it on one post with a small bag from the garden center or such and see how it works for your situation.