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Name: Paul H.
Status: Other
Age: 30s
Location: N/A
Country: N/A
Date: January 2004


Question:
When water expands as it freeze, how much force (ie. psi) does it exert. Application: if a say a crack in a foundation wall freezes with water in it, How much force would be exerted in that crack.



Replies:
It depends on the temperature. At 0 degrees Centigrade, a very small pressure increase will melt ice. As the temperature drops, the pressure required to melt ice increases rapidly, by approximately 145 atmospheres per degree Centigrade. At -22 degrees Centigrade, ice can exert 2,700 atmospheres (~40,000 lbs. per square inch) of pressure without melting. (Data are from the web page http://www.benbest.com/cryonics/pressure.html) Beyond this temperature and pressure, things get complicated because there are many different forms of ice.

Tim Mooney


This is a bit more involved than it appears. Suppose you start with a mixture of ordinary ice (called ice I) and water at a temperature of 0 C. in a cylinder with a moveable piston and a pressure gauge at 0 to 1 atm applied pressure i.e. the vapor pressure of ice/water at 0 C. If you apply an additional pressure, the ice will begin to melt. The piston will squeeze the less dense ice phase into the more dense liquid phase.

In order to maintain the ice / water equilibrium the temperature will have to be decreased. This process will continue until the pressure reaches about 2040 atm and at a temperature of about -22 C.

At this temperature and pressure a new crystal structure (called ice III) begins to form. It is in equilibrium with both (ice I) and liquid water (no vapor is present). This is a new triple point of water between the three phases (ice I, ice III, liquid water). Then things get even more complicated.

Water has (at my last count) some 13 solid phases that differ in their crystal structure!!! A good web site that will take you through this maze is: http://www.sbu. ac.uk/water/phase.html

This complexity is interesting because these various ice-forms may exist on other planets / moons in their "natural" state. Some high pressure forms of ice "melt" at temperatures well above 0 C. A specific case is the equilibrium of (ice VI, ice VII, and liquid water) which occurs at about 82 C.!! Fascinating stuff this common substance H2O.

Vince Calder


Paul H.,

The only information that I can share with you is regarding Low Carbon Steel Pipe Burst Pressures. To give you an idea of what kind of pressure is exerted when water freezes, take a 1 inch outside diameter pipe with a wall thickness of 0.065 inch. This pipe will be able to withstand a pressure of 7563 pounds per square inch before bursting. I hope that this information regarding your question.

Sincerely,

Bob Trach



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