Concrete and fence posts, can you use dry concrete?

Question

I always mix the crete before I pour it in the hole.

I seem to know a lot of people who just fill it with dry crete.

They insist that over time the crete hardens properly (some of these guys are actual contractors). They say after a couple of rains it's just fine.

I can't believe that this is valid... I just can't.

Am I wrong?

Answer 1

Good question, and I too see many answers assuming DRY mix will be OK. I also answer a lot of CAN I questions with,,, CERTAINLY, then add, But you may not be satisfied.

   There are more than one illogical notions in a hole with dry concrete,and most especially any notion that nature follows any contractors plan.

   Assume for a moment that one is digging footers for a deck or fence post. First of all, logic and physics might suggest that water would have to leach to a center point, and through all the material, for consistency. Then assume it might agitate the aggregate??? Then assume that may happen in the first inch or so, of dry mix, then no rain, for days, then dry/set/cure, of whatever did get wet, leaving instability in the balance of the mix.

   That scenario isn't something I want my name on, or a two ton deck.

   I mean no real offense to any who post fences this way, or decks they intend to use the following day, but I'd shy away. I'm a poet, but I know it.

Steven Wolf

Just my two "sense"

Answer 2

You can put dry mix in the hole, but you have to add water right away and mix in the hole.  This saves you from mixing in a bucket.

Like others said if you just put dry mix and cover it up with no water, you basically just wasted your money.  You would be better off just using dirt and watering it in.

Answer 3

Putting the dry mix into the hole is ok, but there is no guarantee that water will make it to the bottom on the mix, also the mixing action makes it stronger because the lime mix which is the activator for the concrete mix will be distributed through the mix and make a much stronger final product.

Answer 4

Pre mix the concrete before it is put in the hole. A dry mix will not leach in to the middle of the hole, so you get just a surface set of the com[pound. If someone does the dry bag method, replace them, they have no idea of what they should be doing. The water must be mixed through the whole area.  The concrete works much like pancake mix or flour.  Take a cup of flour, pour some water on it and let it sit until the water is absorbed.  Then pour it out. There will be dry areas in the cup, but a hard surface over the flour where the water was touching.  Barrels of flour have been retrieved from sunken ships and only the surface is damaged by the water.

Answer 5

We do this a lot and it works fine you pour the dry mix in the hole add water then mix it with a stick by pressing down and it is as hard as if you pre mixed it.

Answer 6

You're just like me.  I've heard the same thing too.  Bottom line is this though...If you want to know for sure those fence posts are gonna be rock-solid, you just HAVE to mix it and I make sure I put enough in the hole to go a little above ground level and taper down so water will shed away from the post to prevent early rotting.  I just did a small fence yesterday.  MIXIT!