324 AisrisruAL kepoets of department of ageiculttjre. 



aggregates in cooperation with the American Society for Testing 

 Materials. 



Instructions in the work done by the physical laboratories were 

 given during the year to six civil-engineer students. 



chemical investigations. 



The work of the chemical and petrographic laboratories has been 

 carried out under the supervision of C. S. Reeve, chemist. During the 

 fiscal year 419 samples were examined in the chemical laboratory, 

 representing the largest amount of work in its history and an in- 

 crease of 28 per cent over the number of samples received the pre- 

 vious year. Whereas formerly the bulk of the routine work con- 

 sisted in the examination of samples from outside sources, the in- 

 crease in the volume of construction and maintenance work coming 

 directly under the supervision of the office has necessitated the ex- 

 amination of numerous samples for the purpose of controlling the 

 products used. For those cases where the quantity of the product 

 warrants it, a system of inspection at the plant of the manufacturer 

 has been organized. The followirfg inspections were cared for in 

 this manner: 



Oil asphalt for Maine post road gallons— 453, 830 



Oil asplialt for Mount Vernon avenue exiierimental road do 41, 500 



Fluxed native asphalt for Mount Vernon avenue experimental 



road gallons__ 41, 500 



Culvert metal for Maine post road sheets— 1,102 



Culvert metal for Fairfax County, Va., post road do 448 



Culvert metal for Texas post road do 737 



Continued study has been given to Florida conditions with a view 

 to further utilization of local materials, and more particularly for 

 the purpose of developing forms of bituminous sand construction. 

 Under laboratory supervision mixed bituminous sand sections were 

 constructed at West Palm Beach and Ocala, Fla., and a short section 

 by the la^^^er method was laid at Jupiter, Fla. The laboratory also 

 supervised construction of additional oil-coralline rock and oil-marl 

 sections at Buena Vista and Ocala, respectively. The results ob- 

 tained to date in the latter type of construction now form the basis 

 of definite recommendations for extensive work of this character. 



Papers on " Determination of the value of bitumino-us construc- 

 tion " and " Maintenance cost system used on United States experi- 

 mental road " were issued from the laboratoiy. The latter was pre- 

 pared in cooperation with the Division of Maintenance. 



Pesearch work has been continued along the lines indicated in the 

 last annual report and, while results of value have been obtained, 

 they are not sufficiently complete to warrant immediate publication. 

 Additional work has been undertaken for the purpose of devising, 

 if possible, a more practical standard needle for the penetration test, 

 and to thoroughly study the effect of the method of preparing the 

 sample upon the values obtained in this test. Methods of improving 

 the fixed carbon test to make it applicable to materials which foam 

 are also under investigation. The bulletin on methods of testing 

 bituminous road materials is partially revised and will be published 

 at an early date. 



The petrographic laboratory examined and classified 536 samples 

 of rocks for road building, making a grand total of 955 samples 



