2 BULLETIN 230., U. S. DEPARTMENT OF AGRICULTURE. 
If concrete could be made less absorbent of moisture and less porous, 
its ability to withstand the penetration of water would be greatly 
increased, and the material would then be a much more desirable one 
for structures in which it is now used with only partial success. 
OIL-MIXED CONCRETE. 
While experimenting in the Office of Public Roads in an attempt 
to develop a nonabsorbent, resilient, and dustless road material, one 
capable of withstanding the severe shearing and raveling action of 
automobile traffic, the writer's investigations led him into a very 
promising discovery. He found that when a heavy mineral residual 
oil was mixed with Portland cement paste it entirely disappeared in 
the mixture, and, furthermore, did not separate from the other ingre- 
dients after the cement had become hard. The possibilities of oil- 
cement mixtures for waterproofing purposes were recognized, and 
extensive laboratory tests were immediately begun to determine the 
physical properties of concrete and mortar containing various quan- 
tities of oil admixtures. 
These tests have now extended over a period of considerably more 
than two years. Many valuable data have been obtained, through 
both laboratory and service tests, which demonstrate very defi- 
nitely the worth of oil-mixed concrete in damp-proof and waterproof 
structures. Detailed results of these various tests are given in the 
appendix. The conclusions so far reached may be summarized briefly 
as follows : 
It has been shown that the admixture of oil is not detrimental to 
the tensile strength of mortar composed of 1 part cement and 3 parts 
sand when the oil added does not exceed 10 per cent of the weight 
of the cement used. The compressive strength of mortar and of 
concrete suffers slightly with the addition of oil, although when not 
to exceed 10 per cent of oil is added the decrease in strength is not 
serious. Concrete mixed with oil requires a period of time from 50 
to 100 per cent longer to set hard than does plain concrete, but the 
increase in strength is nearly as rapid in the oil-mixed material as in 
the plain concrete. 
Concrete and mortar containing oil admixtures are almost per- 
fectly nonabsorbent of water and are therefore excellent materials to 
use in damp-proof construction. The addition of oil, however, does 
not appear to increase to any great extent the impermeability of con- 
crete subj ected to heavy water pressure, and this method alone will 
probably not make the concrete proof against the actual percolation 
of water through the mass. It has been found that strict attention 
to the details of proportioning, mixing, and placing concrete accom- 
plishes more toward making it waterproof or impermeable than the 
addition of any extraneous material. On the other hand, no amount 
of care in connection with the preparation of concrete prevents the 
