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BULLETIN 1132, U. S. DEPARTMENT OF AGRICULTURE. 



CRUSHING STRENGTH OR COMPRESSION TEST. 



This test is made upon a cylindrical test specimen 2 inches in 

 diameter and 2 inches high. Both ends of tne specimen, which 

 have been sawed at right angles to the axis of the cylinder, are 

 carefully ground to plane surfaces. The cylinder then is crushed 

 in a 200,000-pound Universal testing machine at a speed of 0.1 inch 

 per minute. A small 2-inch spherical bearing block is placed between 

 the moving head of the machine and the specimen. The average 

 of at least two determinations is reported as the crushing strength, 

 calculated in pounds per square inch. Crushing strength tests are 

 made only when specifically requested. 



INTERPRETATION OF RESULTS OF PHYSICAL TESTS. 



To interpret the results of the physical tests of road-building 

 rock, the Bureau of Public Roads has adopted a table of general 

 limiting test values for broken stone for the various types of road 

 construction. For general reference, these limiting values, together 

 with comments upon limits shown, are given in Table 3. By com- 

 paring the results of tests on a sample of rock with the limits shown 

 in the table a general idea of the types of road construction for 

 winch it is best suited may be obtained. It must be emphasized, 

 however, that these values represent average conditions only. For 

 any given material a number of factors such as type of stone, character 

 and volume of traffic, and the character of available material will 

 influence the interpretation to be given the results of the tests. 

 Table 4 contains the total number of rock samples received from the 

 various States which have been tested between January 1, 1916, 

 and December 31, 1921. 



Table 2. — Results of compression tests of rock, made prior to Jan. 1, 1916. 



ARKANSAS. 



Serial 

 No. 



Locality. 



County. 



Name. 



Crushing 



strength 



pounds pei 



square inch 



6331 



Bald Knob 



White 





19, m 











CONNECTICUT. 



9791 



Oneco. 



Windham Biotite granite 



16,63£ 



ILLINOIS. 



4422 

 5509 

 6053 

 8711 

 4660 

 7.509 

 7510 

 4764 

 55.50 



ooss 



6165 

 6865 

 7298 

 7299 

 7300 



Embarras... 

 Thornton . . . 



do 



Hillside 



Tunnel Hill. 

 Reevesville. 



do 



Kankakee . . 



do 



do 



do 



do 



do 



do 



.....do 



Coles 



Cook 



do.... 



do 



Johnson . . . 



do.... 



do 



Kankakee . 

 .do. 



Limestone 



Dolomite 



do 



Argillaceous dolomite. . 



Sandstone 



Argillaceous limestone . 



do 



Dolomite 



.do. 



.do Argillaceous dolomite . 



.do. 

 .do. 

 .do. 

 .do. 

 .do. 



Dolomite. 



do 



Argillaceous dolomite . 



do 



do 



