BUREAU OF PUBLIC ROADS. 393 



Survey, covering all of Maryland east of the meridian passing 

 through Washington, all of the coast counties of New Jei^sey, all of 

 Florida south of Jacksonville. These maps were delivered to the 

 Corps of Engineers. In addition to these detailed highway maps, 

 the principal highways in a zone extending from Boston to New- 

 port News, through New York and Washmgton, were plotted on 

 topographic sheets for the use of the Geological Survey in the prep- 

 aration of aeroplane maps. Detailed route maps were prepared 

 covering the army truck route from Detroit to Baltimore, this work 

 being done in cooperation with the United States Geological Survey 

 and the Corps of Engineers. 



At the request of the Frankford Arsenal, Philadelphia, this bureau 

 worked on a device for testing the power of explosives, with the idea 

 of obtaining autographic record of the force and speed of the 

 explosive. 



Our large Page impact machine was borrowed by the American 

 University for research work in connection with high explosives. At 

 the present time impact machines of the type employed by this 

 bureau are being used in practically' all of the arsenals throughout 

 the country in their routine investigations of explosive materials. 



In cooperation with the concrete ship department of the Ship- 

 ping Board this testing laboratory of this bureau was requested to 

 make several series of tests in order to obtain desired information 

 permitting of the safer design of reinforced concrete ships. 



TECHNICAL INVESTIGATIONS AND TESTS RELATED TO WAR PROBLEMS CARRIED 



ON BY THIS BUREAU. 



In view of the uncertainty of the protection of the steel by the 

 concrete against the action of salt water, tests were made with bars 

 coated with various kinds of paint coatings and metal coating to 

 determine (a) the protection ottered by these coatings against corro- 

 sion, and (h) the effect of the coatings on the bond strength. Some 

 24 coatings were tested, involving about 250 specimens. 



In the design of a concrete ship the shear stresses are very 

 high, and in order to use as little steel and concrete as possible 

 it was necessary to use very much higher unit stress in shear than 

 in ordinary reinforced concrete construction. As no test results 

 were available to indicate what would be a safe unit stress to use 

 with the exceedingly rich mixture of concrete, it was necessary to 

 make a number of beam tests to determine this point. The mate- 

 rials were supplied by the Shipping Board. 



Because of the extremely thin walls containing a large percent- 

 age of reinforcing steel, it was necessary t<) determine how best to 

 ])our the concrete so that it would entirely surround the steel and 

 form smooth surfaces and yet be of consistency dry enough to 

 produce the densest possible concrete. A specimen resembling the 

 shell of a concrete vessel was made up and concrete was poured 

 into the form and the form rapidly vibrated by hammering the 

 sides. The forms were later stripped off and the specimen ob- 

 served. The first metliod of pouring was a complete success and 

 no further experiments were necessary. 



Assistance was given to the Bureau of Standards in the pour- 

 inor of a ]iirfre reinforced concrete specimen designed to resemble 

 151352" 19 26 



