Great! Don't worry about waiting a week or two on the concrete. Next day or two is fine. You're not holding up a multi story building or anything.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Really? So, if I did 3 on a Thursday, I could put the 6 x 6 on them on a Saturday? Once I get them vertical, I should be fine then. The 12-footers must weigh over 100 pounds -- they are heavy suckers.

If you are putting the 6x6s in metal anchors or bases (like a wet anchor), I do not think tapcons will hold in the concrete that soon. Do not think it will set up enough in two or three days; just a guess but would wait a week.

Just a thought. Not a concrete expert.

I dont know either but I am a chicken overall so I will wait at least a week if not two ...although Tom probably forgot more about construction than I will ever know. I just did 6x6 x 8 foot tall to repair my fence and I let the concrete set for two days. Those posts went into holes, 24" down. After 2 days, they really did not move at all with a good tug and shake. Sitting on top of the concrete is a different concept so I will play it safe.

The "official"($$$) way to tie a post to a concrete base is with those standoff things.

The farmer way is to set a 1/2" pin in the concrete and drill a matching hole in the post.

I've never seen either fail.

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It cannot hurt!

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Keep the concrete wet. If it's hot, wet it 3 or 4 times a day. Three days, it's going to be sort of green still. I've read that concrete that was poured underwater continues to cure and get harder for years.

But Tom makes a good point, it will be fairly hard after 3 days, as long as you don't beat up on it shouldn't be a problem. If you use these would be easier to hit it soon, no need for any drilling:

https://www.homedepot.com/p/Simpson-Strong-Tie-PBS-6-in-x-6-in-Galvanized-Standoff-Post-Base-PBS66/202092496?MERCH=REC-_-PIPHorizontal2_rr-_-100375346-_-202092496-_-N

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1986 300SDL, 362K
1984 300D, 138K