Chilling Experience
Chilling Experience
(OP)
Okay fellow engineers. After 20 years in the business and thinking that I have seen it all, guess what? I have not.
A client called me to investigate a 18 kip liquid nitrogen concrete pad. They accidentally spilled LN2 on the footing and it is cracking big time in one corner. The boiling temperature of LN2 is -273 degrees F.
I have few questions:
1.How does the concrete react to the temperature shock?
2.How do the rebars react to the temperature shock?
3.How deep and far in plan are the thermal effects on the concrete?
4.Should the pad be repaired or should it be replaced?
Here is what I am planning on what to do and please let me know your thoughts:
1.Take at least three core samples (ASTM C-42) and test for compressive strength
2.If the samples meet the original strength (3000 psi) it should be okay.
3.If not, perform petro-graphical analysis and see how bad the micro cracks are and how deep they are.
4.If strength is acceptable, repair the cracks in the footing. If strength is bad and the cracks are too many, then replace the entire pad.
Your input is most welcome.
Lutfi
A client called me to investigate a 18 kip liquid nitrogen concrete pad. They accidentally spilled LN2 on the footing and it is cracking big time in one corner. The boiling temperature of LN2 is -273 degrees F.
I have few questions:
1.How does the concrete react to the temperature shock?
2.How do the rebars react to the temperature shock?
3.How deep and far in plan are the thermal effects on the concrete?
4.Should the pad be repaired or should it be replaced?
Here is what I am planning on what to do and please let me know your thoughts:
1.Take at least three core samples (ASTM C-42) and test for compressive strength
2.If the samples meet the original strength (3000 psi) it should be okay.
3.If not, perform petro-graphical analysis and see how bad the micro cracks are and how deep they are.
4.If strength is acceptable, repair the cracks in the footing. If strength is bad and the cracks are too many, then replace the entire pad.
Your input is most welcome.
Lutfi






RE: Chilling Experience
A small LN2 spill on concrete would immediately boil and run off the pad. The only way the pad could be seriously cracked would be by total immersion in LN2.
Was it a small spill or a complete loss of LN2 from the tank?
I would guess that it's more likely that someone dropped a filled, portable LN2 tank on the corner and cracked it simply from the mechanical shock damage.
TTFN
RE: Chilling Experience
Your investigative approach is correct.
RE: Chilling Experience
RE: Chilling Experience
RE: Chilling Experience
Thanks everyone for your input.
Lutfi
RE: Chilling Experience
RE: Chilling Experience
RE: Chilling Experience
Needless to say, the footing will be repalced.
Tahnks everyone for yoyur help.
Lutfi