338 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



ROAD MATERIAL TESTS AND RESEARCH. 



Prevost Hubbard, Chief. 



The Division of Road Material Tests and Research was created 

 July 1, 1915, consolidating all laboratory routine and research work 

 of the office under one head. This arrangement permitted material 

 reduction of the clerical force previously assigned to this branch of 

 the work, effected simplification of the files, elimination of unneces- 

 sary forms and records, and secured closer cooperation between the 

 various laboratories. 



One thousand four hundred and fifty-three samples of road mate- 

 rial were analyzed or tested in the laboratories in the fiscal year, an 

 increase of nearly 40 per cent over the preceding year. 



ROUTINE CHEMICAL TESTING AND INSPECTION. 



Four hundred and seventy-four samples were examined in the 

 chemical laboratory. This is a greater number than for any pre- 

 ceding year and represents an increase of about 13 per cent over the 

 last fiscal year. Of these samples 338 were bituminous materials, 115 

 metal, and 21 rock, sand, cement, and miscellaneous materials. 



PHYSICAL TESTS OF ROAD-BUILDING MATERIALS. 



The office continued its policy of testing free of charge for any 

 citizen of the United States samples of rock, slag, gravel, sand, etc., 

 for road -building purposes. The physical laboratory tested 979 

 samples, an increase of about 55 per cent over the last fiscal year. 

 Of these samples 577 were rock and slag, 160 gravel, 155 sand, clay, 

 soil, etc.. 31 cement and concrete, and 56 miscellaneous. 



Samples were received from every State in the Union except Wyo- 

 ming, the more important distribution being as follows: Georgia, 

 182; Virginia, 155; West Virginia, 57; North Carolina. 50; Indiana, 

 50; Ohio. 49; Pennsylvania, 45; Maryland. 43; Florida, 42; Ten- 

 nessee. 38; Texas, 32; South Carolina. 31; Michigan, 27; and New 

 York, 21. 



MICROSCOPIC EXAMINATION AND CLASSIFICATION OF ROAD-BUILDING ROCK. 



The microscopic laboratory examined and classified 881 samples 

 of road-building material, an increase of about 62 per cent over the 

 last fiscal year. Of these, 574 were rock and slag, 295 gravel, sand, 

 cla}', etc., and 14 miscellaneous. 



RESEARCH ON DUST PREVENTIVES AND ROAD BINDERS. 



A paper upon "The Effects of Exposure on Tar Products" was 

 prepared and will be published at an early date. A laboratory inves- 

 tigation of the suitabilit}' of bituminous materials for use in the 

 construction or treatment of earth roads has developed a method of 

 incorporating asphalt with earth without the preheating of the 

 earth. This investigation has resulted in the construction of an 

 experimental asphalt-earth road. 



The construction of an experimental refining plant for petroleum 

 and tar products was practically completed. This plant will be used 

 for the purpose of determining what effect variations in refining 

 methods produce on the physical and chemical characteristics of 

 oils and tars. 



