24 THE TESTING OF ROAD MATERIALS. 



observation extending over a period of less than one week was not of 

 sufficient duration to represent the entire absorptivenesfl of the brick. 

 The directions given for conducting the test were to weigh five 

 abraded bricks after drying for fort} T -eight hours at a temperature of 

 250 F., then immerse them for forty-eight hours and reweigh. 



The cross breaking and compression tests were left optional. For 

 the former test knife-edges rounded both transversely and longitudi- 

 nal^ were recommended and ten bricks were to be tested. For the 

 latter test five half bricks were to be used and loaded on edge through 

 plaster of Paris beds. 



About the same time a study of the rattler test was conducted at the 

 University of Illinois by A. N. Talbot to determine the proper com- 

 position of an abrasive agent for use in the rattler test. It appeared a 

 that it was necessary to use a mixture of large and small cast-iron shot 

 in order to distinguish between soft and hard brick in the rattler test. 



Minor studies of the rattler test were made at Purdue University 

 by W. K. Hatt 6 and at the State Agriculture College of Iowa by 

 A. Marston/ The former showed that the moisture condition of the 

 brick was important. The latter made a study of the cross-breaking 

 t ;s1 and showed that the large variation in individual results was due 

 to real differences in the quality of the bricks tested. 



Gomer Jones d described a rattler in which the bricks were held in 

 pockets cast on the staves so that the interior of the rattler was lined 

 with brick, on the surface of which lining the shot filling rolled and 

 produced impact and abrasion. The committee on technical investi- 

 gations of the National Brick Manufacturers' Association subjected 

 Talbot's "shot process" and the Gomer-Jones process to a thorough 

 examination by comparing the action of the two processes on bricks 

 of known grade. The results reported in 1900 e favored the use of 

 that form of shot suggested by Talbot, and a new standard of the 

 National Brick Manufacturers' Association, which proscribed a shot 

 filling, was accordingly adopted. The Jones rattler was found to be 

 mechanically defective. This rattler was improved by Talbot and a 

 new investigation of the action of the improved rattler compared \\ ith 

 the action of the standard process was instituted. The results given 

 in a preliminary report of the committee of the National Brick Manu- 

 facturers' .Wociation in Aui:u>t. l'.nl. showed that reliance could he 

 placed on both the standard process and the ( Joiner-Jones proco- afl 

 modified by Talbot. A description of the standard method as finally 

 adopted by the National Brick Manufacturers' Association will In- 

 given among the methods <f the Road Material Laboratory. 



" The Technograph, University of Illinois. No. 12, 1898. 

 ^Proceedings Indiana Engineering Society, 1899. 



c Proceedings Io\va F.iiiriiit'rrini: Society, 1899. 

 ^Columbus Meeting of N. V>. M. A.. 1899. 

 * Detroit Convention, February, 1900. 



