A1JBASION TKST. 25 



METHODS AND TESTS OF THE ROAD MATERIAL LABORATORY. 



The Road Material Laboratory was established in December. I'.MMI, 

 in the Bureau of ChemiMry. Up to the promt time reporN have 

 been made on about live hundred samples, representing a geographical 

 distribution over thirtx -eight States of the Union and including :t 

 number of samples from Porto Rico and Cuba. 



The primary object of this laboratory is to make standard tests ,,, 

 road materials, free of charge, for eitixens of the United States. In 

 addition to this allied problems may be presented for studv. sueh as 

 the suitability of clays for the manufacture of paving bricks, drain 

 tiles, cements, etc., the testing of cements and concretes for road 

 foundations, drains, gutters, and highway bridges. It is the intention 

 of the Department to aid as far as possible in the solution of all tin- 

 problems of road building, but more particularly those relating to rural 

 highways. It is not, however, the policy of the Department to under- 

 take scientific investigation or tests of materials for manufacturers or 

 others who desire to use the information thus acquired to promote 

 commercial ends. 



Any person desiring to have road materials tested will, on applica- 

 tion, be supplied with instructions for collecting and shipping samples 

 to this laboratory. The tests as carried on at present are described 

 in the following pages. 



TESTS FOR ROCK AND GRAVEL. , 



ABRASION TEST. 



This test is almost identical with the Deval test already described 

 under the French methods, the only difference being the omission of 

 certain features not deemed strictly necessary, and a few modifications 

 in the machine to simplify its operation and lessen the cost of const ruc- 

 tion. This machine, shown in lig. 1, p. 18, is made entirely of east 

 iron and has given excellent service. The test is made in the follow- 

 ing manner: The sample to be tested is first broken in pieees that will 

 pass in all positions through a 6 cm (2.4-inch) ring, but not through a 

 3 cm (1.2-inch) ring. The stones are then cleansed, dried in a hot- 

 air bath at !()() C.. and cooled in a desiccator. Five kilograms are 

 weighed and placed in one of the cylinders, the cover bolted on. 

 and the machine rotated at the rate of 2,000 revolutions p-r hour for 

 five hours. When the IOJMMI revolutions of the machine are com- 

 pleted the contents of the cylinder are placed on -a sieve of 0. !' 

 cm ( T V inch) mesh, and the material which pa^>e> through i> again 

 sifted through a sieve of 0.02.") cm (o.Ol inch) mesh. Both sieves and 

 the fragments of rock remaining on them are held under running 

 water till all adhering dust is wa>hed oil'. After the fragment- have- 

 been dried in a hot-air bath at 100 C. and cooled in a desiccator they 

 are weighed and their weight subtracted from the original 5 kg (11 



