I built my dock last summer using 16 inch concrete forms and 4x6's with rebar as well. I used ready mix a bag at a time adding water and more mix all the way to the top. The paper cylinders will eventually decompose and disappear. I'm hoping the concrete doesn't crumble and disappear as well. It's pretty solid

Good luck

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Last edited by BonesD; 05/22/19 07:23 PM.