UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 347 j 



Contribution from Office of Public Roads and Rural Engineering r ^U/k~l3IC'* 

 &U LOGAN WALLER PAGE, Director ^^"^^ 



Washington, D. C. PROFESSIONAL PAPER March 17, 1916 



METHODS FOR THE DETERMINATION OF THE PHYSICAL 

 PROPERTIES OF ROAD-BUILDING ROCK. 



By Frank H. Jackson, Jr., Assistant Testing Engineer. 



CONTENTS. 



Page. 



Introduction 1 



Physical properties of road-building rock 2 



Physical tests of road materials 3 



Specific gravity, weight per cubic foot, 



water absorption 3 



Deval abrasion test 4 



Hardness test 6 



Physical tests of road materials— Contd. 



Toughness test 11 



Cementing value test 15 



Compression test 22 



Appendix A.— Selection and shipment of 



samples 22 



Appendix B.— Equipment of laboratory 26 



INTRODUCTION. 



This bulletin is a partial revision of a former bulletin by Albert T. 

 Goldbeck and Frank H. Jackson, jr., issued June 10, 1912. x The 

 first bulletin dealt not only with the method of testing rock for 

 road building, but also gave the results of laboratory tests obtained 

 by the office on all rock samples received to July 1, 1911, together 

 with the interpretation of those tests. It appears advisable to 

 present complete results of tests by the office at rather frequent 

 intervals, so that additional data may be promptly available for 

 the general use of highway engineers. The present bulletin has thus 

 been limited to a description of methods employed by this office for 

 testing rock for road building, and is intended to serve as a more 

 or less permanent laboratory manual for those who have occasion to 

 make such tests. 



Although the methods of determining the physical properties of 

 rock used in macadam road construction have remained essentially 

 the same since the publication of Bulletin 44, experience gained 



> Office of Public Roads Bulletin No. 44, The Physical Testing of Rock for Road Building. 

 17025°— Bull. 347—16 1 



