BUREAU OF PUBLIC ROADS. 517 



Prelimiiiiirv expoiimontal -work was also performed on an investi- 

 gation of blast furnace slag for use as a coarse aggregate in concrete. 



A paper on 'The pressure exerted by concrete against forms" was 

 prepared and presented before the xVmerican Concrete Institute. 



A paper was also published in our bureau magazine, Public Roads, 

 on a new instrument designed and built in the division for measuring 

 the wear of concrete roads under traflic. 



An investigation of the effect on concrete of alkalies in the mixing 

 water has been started. 



NONBITUMINOUS ROAD MATERIAL INVESTIGATIONS. 



An investigation of the chemical composition of blast furnace and 

 smelter slags was made and samples tested from all of the principal 

 slag banks in the country. Melts have also been prepared in the 

 laboratory resembling blast-furnace slag. 



An investigation of the variation in spelter coating on galvanized 

 metal for the fabrication of corrugated metal culvert pipes was con- 

 ducted, as well as a comparison of the lead acetate and antimony 

 chloride-hydrochloric acid method for determining the amount of 

 spelter coating. Several of the largest plants manufacturing sheet 

 metal for galvanized metal culvert pipes were visited and data col- 

 lected. A paper entitled "Galvanized culverts'' was prepared and 

 published in the May issue of Public Roads. 



As a result of the quarry investigations undertaken during 1917 and 

 1918, the bureau was able to cooperate with the road materials com- 

 mittee of the American Society for Testing Materials in the prepa- 

 ration of tentative standards for sizes of crushed stone. A paper on 

 the subject was presented also at the annual meeting of the Crushed 

 Stone Association at Louisville, Ky. 



A number of concrete roads in the State of West Virginia, in which 

 soft sandstone was used as aggregate, were inspected for the purpose 

 of noting results in service as compared with laboratory tests to which 

 the material has been subjected. 



The study of industrial practice in the preparation of conmiercial 

 broken stone aggregates, continued from the previous year, was car- 

 ried on in eastern Massachusetts, Connecticut, and Virginia. A sta- 

 tistical study was made on the nonbituminous road material sup- 

 plies of 19 Southern and Middle Western States. Road material sta- 

 tistics were compiled through correspondence with a large number 

 of sand, gravel, and broken stone producers in the I'nited States. 

 Information was likewise gotten with respect to Portland cement 

 production as affecting road construction. Santl and gravel pro- 

 duction investigations were made in Maryland. Virginia, Pennsyl- 

 vania, New York, tiie New England States, and Wisconsin. 



PHYSICAL TESTS OF ROAD-BUILDING MATERIAL. 



During the year 1 ,020 samples of road-building materials were ex- 

 amined in the physical laboratory, as compared with 1,084 samples 

 during the ])receding year. The larger number tested during the 

 j)rccoding year is accouuteil for by the testing of a larger numljer of 

 concrete samples submitted from the District of Columbia. The 

 number of samples tested during the past year is well above the aver- 



