8 o6 
Journal of Agricultural Research 
Vol. V. No. 17 
The materials for this work were selected with the idea of obtaining 
products which showed rather wide differences in physical and chemical 
properties. For this purpose four types of oil asphalt were selected, 
which, being practically all bitumen, eliminated to a large extent varia¬ 
tions due to sampling, which might have occurred in the case of native 
asphalts or fluxed native asphalts carrying appreciable quantities of non- 
bituminous material. The types represented in the following tables are 
produced from (i) steam-refined California petroleum, (2) steam-refined 
Mexican petroleum, (3) refined blended petroleum, and (4) blown pe¬ 
troleum. Three grades of each type were selected, having, at 25 0 C., 
under a load of 100 gm. applied for 5 seconds, penetrations of approxi¬ 
mately 50, 100, and 150. This made 12 samples in all, and it is believed 
that the results obtained by their use can consistently be interpreted to 
cover practically all types of asphalts and asphalt cements. The more 
important physical and chemical characteristics of these products are 
shown in Table I. 
Table I .—Characteristics of asphalt cements 
The first consideration which naturally presents itself is the method 
of preparing the sample for the test. It is apparent that in order to 
duplicate results upon different samples of the same material the samples 
shall be taken so as to represent the entire body of material sampled. 
