422 ' ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



Heavy Motor Truck Traffic was presented before the Aiiiorican Road 

 Builders' Association. 



EXPERIMENTAL BITUMINOUS ROAD CONSTRUCTION AND MAINTENANCE. 



As during the previous year, supervision and inspection of experi- 

 mental bituminous roads has been confined largely to the vicinity 

 of Washington. One inspection was made, however, of the road 

 between Boston, Mass., and Portland, Me., and between Portland 

 and Bowdoinham, Mass. 



NONBITUMINOUS ROAD MATERIAL INVESTIGATIONS. 



The quarry investigations begun during the previous year to study 

 industrial practice in the preparation of commercial broken stone 

 aggregates with a view to standardization of sizes and to obtain cost 

 data, etc., was continued and an extensive study was made of the 

 quarries in the South and in eastern Massachusetts and of two quar- 

 ries near Poughkeepsie, N. Y. Altogether 64 inspections were made 

 of crushed stone producing plants. Papers written as a result of 

 these investigations appeared in the September, 1918, and the June, 

 1918, issues of Public Roads. 



A large number of brick roads were inspected throughout Ohio, 

 Indiana, Illinois, Iowa, Nebraska, and Missouri, in order to make a 

 detailed study of failures in this type of road, and a report on these 

 inspections Avas published in the February, 1919, issue of Public 

 Roads. A large number of slag-concrete roads were also inspected 

 in the vicinity of Youngstown, Ohio, and a report was prepared on 

 this inspection. 



STANDARDIZATION OF METHODS OF TESTING BITUMINOUS ROAD MATERIALS. 



Cooperation with the American Society for Testing Materials was 

 continued through the Committee on Bituminous and Nonbituminous 

 Road Materials. The following investigations will be of direct bene- 

 fit in the standardization work of committee D-4 : 



Asphalt content of oils. 

 Comparison of volatilization tests. 

 Chemical composition of asphalts and tars. 

 Methods of making float tests. 



STANDARDIZATION OF METHODS OF TESTING NONBITUMINOUS ROAD MA- 

 TERIALS. 



Tests were continued on a revised standard abrasion test of rock 

 and a study is being made of an abrasion test for gravel. Steps were 

 also taken during tlie year to study a new abrasion test for concrete. 

 A new abrasion test for stone block is also being standardized and 

 the results are available for the standardization work of the road 

 materials committee of the American Society for Testing Materials. 



CONCRETE INVESTIGATIONS. 



A large number of tests were made for the concrete-ship depart- 

 ment of the United States Shipping Board on the bond strength of 

 steel reinforcing bars coated with i^rotective coatings. Tests were 



