UNITED STATES DEPARTMENT OF AGRICULTURE 



.,««M BULLETIN No. 370 ^^,^,.„ 



N all^ ^^l^ly Contribution from Office of Public Roads and Rural Engineering '^Aji^^aJ^^ 

 ^3^'^^^ LOGAN WALLER PAGE, Director O'^V VwL 



Washington, D. C. PROFESSIONAL PAPER July 20, 1916 



THE RESULTS OF PHYSICAL TESTS OF ROAD- 

 BUILDING ROCK. 



By Pr|;vost Hubbard, Chemical Engineer, and Frank H. Jackson, Jr., Assistant 



Testing Engineer. 



CONTENTS. 



Page. I Page. 



Introduction 1 



Agencies causing road deterioration — 2 

 Factors influencing the selection of 



rock for road building 2 



Physical properties of road-building 



rock 3 



Variations in results of tests 5 



Interpretation of results of physical 

 tests 9 



Table IV. — Geographical distribution 

 of samples tested 12 



Table V. — Results of physical tests of 

 road-building rock 13 



INTRODUCTION. 



The purpose of this bulletin is to furnish highway engineers with 

 the results of physical tests of road-building rock made in the labo- 

 ratories of the United States Office of Public Roads and Rural En- 

 gineering to January 1, 1916. It is proposed to revise this bulletin 

 from time to time, so that additional data secured by the office may 

 become promptly available. Detailed descriptions of the methods 

 of determining the physical properties of road-building rocks have 

 been given in a recent publication by Jackson.^ Interpretation of 

 the results of these tests has, however, been reserved for publication 

 with the tabulated data here given. It should be noted that Bul- 

 letins Nos. 347 and 370 therefore constitute a complete revision of 

 Office of Public Roads Bulletin No. 44, by Albert T. Goldbeck and 

 Frank H. Jackson, Jr., which was published in 1912. As a matter 

 of interest it may be stated that since January 1, 1912, approximately 

 1,350 additional samples have been classified and tested, raising the 

 total number from the United States and Canada to about 3,650. 



1 United States Department of Agriculture Bulletin No. 347. 

 31693°— Bull. 370—16 1 



