[TowerTalk] concrete forms

[Nick Pair]

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 soil.
   
  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.
   
  73
  Nick 
  WB7PEK

 		
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