HKlllWAY CONSTRUCTION H3 



iron, not chilled or case-hardened. The staves shall preferably be 

 composed of steel plates, since cast-iron peans and ultimately breaks 

 under the wearing action on the inside. There shall be a space of one- 

 fourth of an inch between the staves, for the escape of dust and small 

 pieces of waste. Other machines may be used, having from twelve to 

 sixteen staves; but if this is done, a record of it must be attached to 

 the official report of the test. 



3. Composition of the Charge. All tests must be executed on 

 charges containing but one make of brick or block at a time. The 

 charge shall consist of 9 paving blocks or 12 paving bricks, together 

 with 300 pounds of shot made of ordinary machinery cast-iron. This 

 shot shall be of two sizes, as described below; and the shot charge shall 

 be composed one-fourth (75 pounds) of the larger size, and three- 

 fourths (225 pounds) of the smaller size. 



4. Size of the Shot. The larger size shall weigh about 7 y pounds 

 and be about 2J inches square and 4J inches long, with slightly round- 

 ed edges. The smaller size shall be cubes of 1 J inches on a side, with 

 rounded edges. The individual shot shall be replaced by new ones 

 when they have lost one-tenth of their original weight. 



5. Revolutions of the Charge. The number of revolutions of a 

 standard test shall be 1,800; and the speed of rotation shall not fall 

 below 28 nor exceed 30 revolutions per minute. The belt-power shall 

 be sufficient to rotate the rattler at the same speed, whether charged 

 or empty. 



6. Condition of the Charge. The bricks composing a charge 

 shall be thoroughly dried before making the test. 



7. Calculation of the Results. The loss shall be calculated in 

 per cents of the weight of the dry brick composing the charge ; and no 

 result shall be considered as official unless it is the average of two 

 distinct and complete tests made on separate charges of brick. 



Absorption Test 

 L The number of bricks for a standard test shall be five. 



2. The test must be conducted on rattled brick. If none such 

 are available, the whole brick must be broken in halves before treatment. 



3. Dry the bricks for 48 hours at a temperature ranging from 

 230 to 250 F. before weighing for the official dry weight. 



4. Soak for 4S hours completely immersed in pure water. 



