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[TowerTalk] concrete forms

Subject: [TowerTalk] concrete forms
From: Nick Pair <>
Date: Mon, 31 Jul 2006 10:38:24 -0700 (PDT)
List-post: <>
A couple of notes on bases:
  1; Concrete tales 30 days to reach 90% ultimate strength under average 
conditions.  Heat, dryness, and mix will vary this time but usually to the 
longer side. The so-called high/early will reach the 65% to 80% quicker but 
still take as long to reach the ultimate strength. Putting stress on concrete 
too early with a tower is a sure way to develop cracking and prevent the 
concrete to achieve a homogeneous mass as desired.
  2: Just a layer of 4 or 6 mill plastic stapled over form boards will prevent 
sticking and the plastic is available everywhere.
  3: Concrete poured over undisturbed soil will give you the load bearing 
capacity that the base size was based on. Any soil or added gravel must be 
compacted to at least 90% of its compact-ability to be equal to undisturbed 
  4: The "drying" of concrete is actually a curing process. The cement in the 
concrete mix is reforming the crystal formation it had as limestone before it 
had all the water baked out of it in the kiln at the concrete plant. Its more 
of a chemical process that yields a crystal and some heat . The heat is a enemy 
of concrete curing and in larger pours must be accounted for. In the warmer 
temps of summer you should never allow concrete to dry out for the first week 
at least. All good companies that pour large slabs us some form of retardant on 
top of slab to slow evaporation. In our context this means just keep everything 
wet, the soil should be saturated (sand and gravel in bottom should be covered 
with plastic) and water sprayed  at regular intervals on finished concrete. 
Just don't spray hard enough to erode surface.
  5: I agree whole heatedly with others who have stated that compacting the 
soil around base after form removal is difficult and often skimped on believing 
that all will settle in somehow. I hope that no one will skip this crucial step 
and that they will used some form of mechanical compaction and not just stomp 
it down and call it good.
  I"m sure that with all the fine information on this group we will all have 
safe bases under our towers that are sprouting this summer.

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