340 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



scopic particles in solutions of bituminous materials. A considerable 

 amount of the work on standardization of methods was done in co- 

 operation with the committee on road materials of the American 

 Society for Testing Materials. 



STANDARDIZATION OF METHODS OF TESTING NONBITUMINOUS ROAD MATERIALS. 



Department Bulletin 347, " Method for the Determination of the 

 Physical Properties of Koad-Building Rock," was published, and a 

 paper on " The Determination of the Specific Gravity of Non- 

 homogeneous Aggregate " was presented before the American Society 

 for Testing Materials. In addition, investigations have been con- 

 ducted on the standardization of an abrasion test for gravel, a method 

 of determining clay in aggregates, a method of determining the 

 weight per cubic foot of sand, comparison of rational and ordinary 

 sand sieves, method for determining the normal consistency of 

 cement mortars, and the determination of voids in aggregates. 



CONCRETE INVESTIGATIONS. 



An apparatus for measuring the wear of concrete roads was de- 

 vised and used in connection with experimental roads constructed 

 under the supervision of the office. Data pointing directly to a more 

 economical design of bridge floors than has heretofore been used have 

 been secured, and the effect of time of mixing on concrete and the 

 strength of concrete with different kinds of aggregates have been 

 investigated. 



Two papers entitled "Apparatus for Measuring the Wear of Con- 

 crete Roads," and " Tests of Three Large-Sized Reinforced Concrete 

 Slabs Under Concentrated Loading" were prepared and published 

 in the Journal of Agricultural Research, while two papers entitled 

 "Tests of Large Reinforced Concrete Slabs," and "The Flow of 

 Concrete Under Sustained Loads " were presented at the annual 

 convention of the American Concrete Institute in January. An 

 article entitled " Oil-Mixed Portland Cement Concrete," which was 

 prepared during the fiscal year 1915, was published this year as De- 

 partment Bulletin 230. 



ROAD AND BRIDGE FOUNDATION TESTS. 



An apparatus has been devised and constructed for measuring the 

 distribution of pressure through fills and a paper describing such 

 apparatus was presented before the American Society for Testing 

 Materials under the title "An Apparatus for Determining Soil Pres- 

 sures." A building especially designed for conducting these tests 

 is under construction at Arlington Farm and plans have been per- 

 fected for cooperative field experiments with various public-service 



bodies. 



FARM IRRIGATION INVESTIGATIONS. 



Samuel Foktier, Chief. 



The transfer of this division from the Office of Experiment Sta- 

 tions to the Office of Public Roads and Rural Engineering was 

 effective July 1, 1915. The work was carried on under the following 

 projects : 



UTILIZATION OF WATER IN IRRIGATION. 



Experiments to determine the best methods of using water have 

 been carried on in cooperation with the following: State of Arizona 



