876 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



the expansion and contraction of concrete, and the physical testing of 

 rock for railroad ballast. 



The instruction of the student engineers and assistant highway 

 engineers in the testing of road materials has been carried on as in 

 past years. 



CHEMICAL INVESTIGATIONS. 



During the past fiscal j^ear 198 samples were received in the 

 chemical laboratories for examination. 



In addition to the routine work of the laboratory several lines of 

 research were undertaken. This work was mainly for the standard- 

 ization of methods, and includes an investigation into the effect of the 

 diameter of the bitumen holder on the penetration test, and an im- 

 provement or modification of the dimethyl sulphate test for tar- 

 asphalt and tar-petroleum mixtures. The results of these investiga- 

 tions were prepared for presentation before the International Asso- 

 ciation for Testing Materials and the Eighth International Congress 

 of Applied Chemistry, respectively. The improvement of the exist- 

 ing methods of testing or the proposal of new and more accurate ones 

 is an important fimction of the laboratory organization, and re- 

 searches upon the melting point and distillation methods are now in 

 progress. Part of the work has been carried along in conjunction 

 with a special committee of the American Society for Testing Ma- 

 terials, and it is expected that some final recommendation will be 

 made at an early date. The study of the effect of exposure on various 

 types of bituminous materials is producing results of considerable 

 interest, and some of the data thus far accumulated will shortly be 

 published. 



During the year a paper entitled " Organic residues from soluble 

 bitumen determinations " was presented before the American Society 

 for Testing Materials, and an address on " The use of bituminous 

 binders in road construction and maintenance " was made before the 

 Virginia Road Builders' Association. 



The preparation of specifications for bituminous road materials 

 and methods of construction has been continued, and during the fis- 

 cal year 79 specifications were issued, of which 40 were for oil- 

 asphalts and other petroleum products, 26 for refined tars, 5 for 

 fluxed native asphalts, 5 for bituminous construction, and 3 for sur- 

 face treatments. 



Cooperation of the chemical laboratory and engineering force con- 

 tinues to demonstrate its value, and during the year 7 engineer 

 students and 2 highway engineers were given a course of laboratory 

 instruction. The laboratory force particij)ated in field work on 33 

 assignments distributed throughout the United States. 



The work of the petrographic laboratory was essentially a con- 

 tinuation of that of last year. 



Quantitative analj^ses of 85 rock samples were made, while 38 

 samples were analyzed qualitatively, and 301 samples were examined 

 chemically and mineralogically for the purpose of identification and 

 classification. Besides the routine work, the study of blast-furnace 

 and open-hearth slag and Portland cement clinkers was continued 

 to determine the best means of utilizing these products for road- 

 making purposes. 



