THE TESTING OF ROAD MATERIALS. 



INTRODUCTION. 



The Road Material Laboratory was established by the Secretary of 

 Agriculture in December, 1900. Work was not begun, however, 

 until several months later on account of the time necessary to effect 

 its equipment. The fiscal year ended June 30, 1902, was the first year 

 of its operation. The laboratory at present contains all the necessary 

 appliances for making tests on road materials and for investigating 

 some of the more important problems connected with the work. 



The main object of this bulletin is to describe in some detail the 

 methods and work of the laboratory and to give the results obtained 

 up to the present time. Incidentally, the physical, mechanical, and 

 chemical agencies which act upon road materials are discussed and a 

 brief history of the testing of such materials is given. 



The Road Material Laboratory tests road materials, without charge, 

 for citizens of the United States and reports to them the information 

 obtained. In addition to routine tests on samples submitted, investi- 

 gations are conducted for the improvement of road materials. The 

 laboratory is prepared to test rocks, gravels, and clays for road con- 

 struction, tiling, cement and concrete, and paving blocks of stone, 

 brick, wood, asphalt, and bituminous matter. The principal activities 

 may*be classified under the following heads: 



(1) Tests for determining the quality of materials to aid road 

 builders in selecting those most suitable for their work. 



(2) The investigation of various processes to develop simple, appro- 

 priate, and reliable tests. 



(3) The collection of data for use in drawing up specifications for 

 standards of quality. 



(4) Scientific research to develop new materials or mixture^, and 

 the study of problems which may arise in road building. 



The most important work conies under the first head, for the main 

 object of the laboratory is to obtain results, by means of appropriate 

 tests on small samples, which will agree sufficiently well with the 

 results of practice to aid the road builder in selecting the most suitable 

 materials from those available for his work. That the laboratory may 

 serve its purpose, the tests adopted must be of such a nature that they 



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