I'.HU'K AND BUILDING STONE 275 



224. Transverse tests of stone. The use of stone where transverse 

 se is applied calls for some knowledge of its transverse strength. 



ne may meet the specifications for crushing and yet fail entirely 

 when subjected to cross bending, since a beam is in tension on one 

 side and in compression on the other. As stone is much stronger in 

 compression than in tension, it usually fails in tension under trans- 

 verse loading. 



To test the transverse strength of stone, small beams are pre- 

 pared usually 1 in. square by 6 or 8 in. long. These are supported 

 nn knife-edges resting on the platform of the testing machine, and 

 the liad i- applied at the center. Buckley reports limestone beams 

 1 in. x 1 in. X 6 in. to have a modulus of rupture of 2000 lb./in. 2 , 

 and sandstone beams 1 in. x 1 in. X 4 in. to have a modulus of rupture 

 of 1000 Ib. in. 2 . 



225. Abrasion tests of stone. The most extended series of tests 

 of stone in resisting abrasion was made by Bauschinger.* Four-inch 

 cubes under a pressure of 4 lb./in. 2 were subjected to the abrasive 



ii of a disk having a radius of 19.5 in. and making 200 revo- 

 lutions per minute, upon which 20 g. of emery were fed every 10 

 revolutions. The loss of volume in cubic inches was as follows. 



Granite 24 dry and .46 wet 



Liin.^ton.- 1.10 " 1.41 " 



..- 80 " .64 " 



Brick 38 " .75 " 



Asphalt 60 " 1.62 " 



i tests of stone have never been standardized, and comparison 

 of results of different tests must be made with a full understanding 

 of all the conditions affecting the results. 



226. Absorption tests of stone. The absorption test is made to 

 mm** tin- amount of water absorbed by the dry stone. In making 



tlu- test the specimen is first heated for several hours at a tempera- 

 ture of 212 F., and then placed in water for about thirty hours. The 

 in- -n>ase in the weight of the specimen divided by its weight when 

 dry and multiplied by 100 gives the percentage by weight of moisture 

 absorbed. This percentage for a series of tests varied, for granite, 

 from 1.1 to .3 ; for limestone, from 3.6 to 1.2 ; and for sandstone, from 

 to 1.6. 



* Communications, 1884. 



