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Re: Granite's Modulus of Elasticity

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K . Hemmatyar

A good reference for properties of stone: Conservation of Historic Stone
Buildings and Monuments, 1982 Report of the Committee on Conservation of
Historic Stone Buildings and Monuments, National Materials Advisory Board,
Commission on Engineering and Technical Systems, National research Council;
published by National Academy Press, 2101 Constititution Ave. N.W. Washington
D.C. 20418.

A table on page 64 gives the value of Elastic Modulus of granite in Megabars
as 0.3 to 0.6, and modulus of rupture in kilobars as 0.1 to 0.7.  I interpret
a bar to be one atmospheric pressure; say about 15 psi, giving E=4,500,000 to
9,000,000 psi.  

Modulus of rupture is the breaking strength in tension and is in the range of
0.1 to 0.3 times the compressive strength.

If you have the stone tested in a lab, you may see a surprising concave-upward
stress-strain relationship.  Don't be too quick to criticize the lab, as I
once was -- natural internal microcracking causes the stone to get stiffer as
the microcracks close under load.

Nels Roselund
Structural Engineer