UNITED STATES DEPARTMENT OF AGRICULTURE 
jfe BULLETIN No. 370 
mW •Si 
pj$£r Contribution from Office of Public Roads and Rural Engineering *^! 
i^'^wL LOGAN WALLER PAGE, Director J^^^^U 
Washington, D. C. PROFESSIONAL PAPER July 20, 1916 
THE RESULTS OF PHYSICAL TESTS OF ROAD- 
BUILDING ROCK. 
By Pkevost Hubbard, Chemical Engineer, and Feank H. Jackson, Jr., Assistant 
Testing Engineer. 
CONTENTS. 
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 
Page. 
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 Koads 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. 1 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. 317 and 370 therefore constitute a complete revision of 
Office of Public Roads Bulletin No. 11, 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 Q — Bull. 370—16 1 
