﻿VITRIFIED BRICK AS MATERIAL FOR COUNTRY ROADS. 7 



RATTLER OR ABRASION TEST. 



The rattler or abrasion test is undoubtedly the most important of 

 the tests made on paving brick at present. In making this test the 

 specimen brick are subjected to destructive influences very similar 

 to those encountered in actual service, and the results obtained, 

 therefore, indicate very closely the effect which traffic may be 

 expected to produce on a pavement constructed of similar brick. 

 The methods of making the test, of which there were formerly a 

 great many, have undergone repeated changes in order that service 

 conditions may be more nearly approached and also in an effort to 

 bring about uniformity, so that the results obtained may be of the 

 greatest possible scientific value. The method which has been lately 

 recommended by the subcommittee on paving brick of the American 

 Society for -Testing Materials may be briefly described as follows: 



The apparatus necessary for making the test, ordinarily called the 

 rattler, consists of a 14-sided barrel of regular polygonal cross section 

 supported on a suitable frame and fitted with the necessary driving 

 mechanism. The staves, each of which forms a side of the barrel, are 

 made of 6-inch 15.5-pound structural steel channels 27£ inches long. 

 These staves are double bolted to the cast-iron heads of the barrel, 

 which are provided with slotted flanges for holding the bolts. Cast- 

 iron wear plates are bolted to the inside of the barrel heads. The 

 outside diameter of the barrel is 28f inches. 



In this barrel is placed what is known as the abrasive charge. This 

 charge consists of two sizes of cast-iron spheres having respective 

 diameters of 3| inches and If inches and weighing, respectively, 7.5 

 pounds and 0.95 pound when new. Ten of the larger spheres are 

 used, and the number of the smaller spheres is made such that the 

 weight of the entire charge will approximate 300 pounds. The indi- 

 vidual larger spheres are discarded whenever their weight falls to 

 7 pounds or less and the smaller spheres when they become sufficiently 

 worn by usage to pass through a circular opening having a diameter 

 of If inches. 



The test is made by placing a charge of ten representative brick, 

 which have been previously dried at a temperature of 100° F. for at 

 least three hours, in the barrel together with the abrasive charge, 

 and then revolving the rattler 1,800 times. The number of revolu- 

 tions per minute is not permitted to fall below 29J nor to exceed 30J, 

 and the operation is made continuous from start to finish. 



The results of the test are reckoned in terms of the loss in weight 

 sustained by the brick, and this loss is expressed as a percentage of 

 the original weight of the brick tested. In determining the loss in 

 weight, no piece of brick which weighs less than 1 pound is consid- 

 ered as having withstood the test. 



