TESTS OF WISCONSIN BUILDING STONE 



531 



stone which has a compressive strength of less than 10,000 

 pounds per square inch usually results in the formation of 

 two quite well defined pyramids. The pyramids resulting from 

 crushing a stone with a compressive strength of between 10,000 

 and 20,000 pounds per square inch are ordinarily less perfect. 

 The pyramids resulting from testing stone of this class are fre- 

 quently wedge-shaped but more often they are intermediate 

 between a pyramid and a cone. The crushing of cubes having 

 a compressive strength of over 30,000 pounds per square inch 

 usually results in the formation of only one pyramid which has 

 more of a conical than pyramidal outline. 



In crushing the granite and also some of the limestone and 

 sandstone cubes a concentric structure was developed similar 

 to that illustrated in Plate II, Figs. 4, 5, and 6. 



TABLE I. 



CRUSHING STRENGTH 1 

 Ultimate Strength in Pounds per Square Inch. 



Granite and rhyolite : twenty-seven samples 

 from twelve different quarries 



Limestone : thirty-one samples from eleven dif- 

 ferent quarries 



Sandstone : forty-five samples from eleven dif- 

 ferent quarries 



Highest test 



47,674 

 42,787 



13,099 



Lowest test 



12,704 

 6,675 

 1,658 



Average 



27,023.7 



25,312.8 



6,125.0 



TRANSVERSE STRENGTH 



The determination of the modulus of rupture is of as great 

 if not greater importance than the crushing strength. As pre- 

 viously indicated, it is especially valuable in determining the 

 required thickness of a stone which is intended to be supported 

 at the ends, and which carries a heavy weight of superstructure 

 in the middle. 



The modulus of rupture was determined for only two Wis- 

 consin granites. The results in each case were over 2300 pounds 



'For detailed results of individual tests see Bulletin No. IV, Wisconsin Geologi 

 cal and Natural History Survey, "Building and Ornamental Stones," 1898. 



