UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1132 
n, D. C. PROFESSIONAL PAPER March 21, 1923 
THE RESULTS OF PHYSICAL TESTS OF ROAD-BUILDING ROCK FROM 
1916 TO 1921, INCLUSIVE. 
Prepared in the Bureau of Public Roads. 
CONTENTS. 
Page. 
Introduction 1 
Table 1.— Results of physical tests of road- 
building rock from 1916 to 1921, inclusive. . 2 
Crushing strength or compression test 46 
Interpretation of results of physical tests 46 
Table 2.— Results of compression tests of rock 
made prior to January 1, 1916 48 
Table 3.— General limiting test values for 
broken stone 51 
Table 4.— Geographical distribution of rock 
samples tested from January 1, 1916, to 
Januarvl, 1922 52 
INTRODUCTION. 
This bulletin gives the results of tests of all rock made by the 
Bureau of Public Roads from January 1, 1916, to January 1, 1922, 
classified alphabetically according to location. It supplements 
United States Department of Agriculture Bulletin 370, "Results of 
Physical Tests of Road-Building Rock," and replaces United States 
Department of Agriculture Bulletin 670, "Results of Tests of Road- 
Bunding Rock in 1916 and 1917." The results of tests of approxi- 
mately 5,300 samples are now avilable in the two bulletins,- and 
these tests represent road-building material from practically all parts 
of the United States and some parts of Canada, Haiti, the Dominican 
Republic, and Porto Rico. Reference to Table 1, in which the 
results of tests made subsequent to January 1, 1916, are tabulated, 
will show that a test of crushing strength has been made on a number 
of samples, and a column of test results not found in Bulletin No. 370 
is added thereby. Tests of crushing strength made prior to 1916 
are recorded in Table 2. This quality of rock is not determined 
ordinarily when making examinations of their suitability for road 
building, but it is employed often when considering rock for use as 
paving clocks or as railroad ballast. A brief description of this test 
as made by the Bureau of Public Roads is given on page 46. 
19525°— 23— Bull. 1132 1 
