Acetylene torch & concrete
Acetylene torch & concrete
(OP)
Bars extended outside concrete needs to be cut using acetylene instead of saw which can take long time. What is the behavior of concrete when it is torched with acetylene?
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Acetylene torch & concrete
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RE: Acetylene torch & concrete
Your's is a different situation, probably other members might give you their experiences. I'd be hesitant though, unless it was proven otherwise.
RE: Acetylene torch & concrete
For cutting rebar, damage will probably be localized but should check for microcracking in concrete as result. Not a good practice if you can avoid it.
RE: Acetylene torch & concrete
Dear Ron, When you use acetylene on a rebar let's say of size 1 inch. What is the temperature at every 5mm increment away from the torch center? And do you know how and what value the rebar expand for every say 100 Celsius in temperature given grade 60? Some formulas?
RE: Acetylene torch & concrete
RE: Acetylene torch & concrete
RE: Acetylene torch & concrete
RE: Acetylene torch & concrete
RE: Acetylene torch & concrete
It's not the expanding steel that causes the explosion, it's the expanding steam resulting from the residual moisture in the concrete.
RE: Acetylene torch & concrete
concrete will absorb water, it is not just "residual moisture". in addition, aggregates also contain moisture
expanding steel causes the concrete to crack due to tensile stress. steel is a good conductor of heat while concrete is not. the steel will heat up far more than the concrete and expand to a much greater degree and very quickly. This could cause cracking or reinforcing bar debonding within the concrete mass.
RE: Acetylene torch & concrete
If the steel thermal expansion is beyond the concrete crushing strain of 0.0035, then the concrete will break, but if the expansion is less than that, then it won't break. Do you agree with this? Since the temperature of the acetylene in the outside is more.. then breakage will form more from the outside to the inside depending on the bar expansion and concrete straining negotiated. Is the theory correct?
Of course this is ignoring moisture which can burst the concrete so I won't do it but interested to know the above to explain to co-workers.
RE: Acetylene torch & concrete
Just use/specify an abrasive cutoff wheel to cut the bar.
A big one is only slightly slower than oxyacetylene cutting.
Do use/specify goggles and a face shield; abrasive cutoff wheels don't fail gracefully.
Mike Halloran
Pembroke Pines, FL, USA
RE: Acetylene torch & concrete
For those who believe the failure mode of heating the bar with acetylene is tensile stress (in addition to moisture mediated evaporation and explosion). Imagine you have a cylinder of concrete with a bar in the middle. You heat the bar with acetylene, the bar will expand. Isn't it that this will cause compression of the bar outwards. If there is nothing to restrain the cylinder, the cylinder would get bigger from poisson's like effect? Or the tensile stress cracking is due to the concrete expansion causing tension between the fibers as it expands outwards? Please elaborate on the mechanisms you think in addition or in correction of the above.
RE: Acetylene torch & concrete
Mike Halloran
Pembroke Pines, FL, USA
RE: Acetylene torch & concrete
RE: Acetylene torch & concrete