Water Expansion Pressure
Name: Paul H.
Date: January 2004
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.
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.
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.
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
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.
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Update: June 2012