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Old 12-07-2012, 09:41 AM   #16
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Slab Breakdown - (Footer Process)


OK. Normally mixed concrete (1-2-3) without any additives achieves good working strength in about 28 days. Remember the nuclear power plant that collapsed killing all those men because they rushed it?

I have never seen an adjustable lolly column installed with the threaded end down, but I guess you could do it, if you didnt mind cracking your shins on the jacking bar. LOL When I was doing this type of work, I only used the adjustable type for jacking floors into position I used the concrete filled 4 inch steel pipe ones for permanent installation. That gives you the compressive strength of the concrete, and the tensile strength of the steel.

Funny how people do things differently in different areas, or by how they learn.

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Old 12-07-2012, 09:49 AM   #17
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Slab Breakdown - (Footer Process)


jagans, i doubt if filling a lalley column w/conc adds an appreciable increase in its ability to support static loads,,, i always understood it was required for fire code, no ?

no one knows when concrete cures - we can measure testing time ( 24hrs, 7d, & 28d ) & those periods have become accepted as a testing norm,,, we can also set compressive/tensile/flexural goals - when testing reveals the goals have been met, we're satisfied - but conc contines to cure, cure, & cure more ad nauseum
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Old 12-07-2012, 12:07 PM   #18
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Slab Breakdown - (Footer Process)


Not sure if it is for fire or not, good question, but the area of a 4 inch circle is around 12.5 inches. even if the concrete is 2200PSI ( which is really low, 3400 is typical) we are talking about an ability to bear 27,500 lbs of static load per column, correct?
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Old 12-07-2012, 09:59 PM   #19
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Slab Breakdown - (Footer Process)


I've always been under the impression that lally columns were filled with concrete for fire rating as well. Simplifying the concrete compressive strength by area is unreliable as well, as the entire unit of steel column with concrete fill would have to be tested as a complete assembly to give an accurate reading. Most 3.5" steel columns rate in the 13K-18K# area for load, and there's no way adding concrete inside of them will come even remotely close to doubling that. Not to mention, the addition of concrete inside of a steel column is typically a recipe for early deterioration of the steel......

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