OIL-MIXED PORTLAND CEMENT CONCRETE. 5 
absorption of water into the mass. The addition of some water- 
repellent compound appears absolutely necessary to insure this result, 
and for this purpose laboratory tests have shown these oils to be at 
least equal to any other substance that has been used. Laboratory 
tests show that oil-mixed concrete is just as tough and stiff as plain 
concrete, and, furthermore, its elastic behavior within working limits 
of stress is identical with that of plain concrete. 
The bond between concrete and plain-bar reinforcement is decreased 
by the use of oil in the concrete, but when deformed bars, wire mesh, 
or expanded metal is used there is no apparent decrease in the bond. 
With the view of determining what effect the addition of oil to 
cement mortar would have in retarding the action of alkali salts on 
the cement, a series of experiments was conducted which seemed to 
indicate that the action of the salt solution is materially retarded by 
the addition of 5 to 10 per cent of oil to a 1 : 3 mixture. Plate I shows 
a view of a series of briquettes subjected for one year to the action 
of a 10 per cent solution of sodium sulphate. The briquettes in the 
upper row contained 10 per cent of oil; those in the middle row, 5 per 
cent of oil; and those in the bottom row, no oil. 
SERVICE TESTS. 
Two bridge surfaces of oil-mixed concrete were laid during April 
and May, 1910, in the borough of Richmond, New York City. About 
400 feet of street were surfaced in 1910 in the city of Washington. 
Likewise, in the suburbs of Harrisburg, Pa., about one-half mile of 
roadway was laid with a 10 per cent oil mixture. Sections of road- 
way containing oil have also been laid on Hillside Avenue, Jamaica, 
N. Y., and at Chevy Chase, Md. Observations to date show that no 
apparent advantage has been gained in these particular cases by the 
addition of oil. 
Service tests of oil-mixed concrete used as a damp-proofing material 
have also been made. A vault 112 feet long by 18 feet wide in the 
United States Treasury Building was constructed in the fall of 
1910. (Pis. II and III.) The side walls of this vault contain 10 per 
cent of oil based on the weight of cement in the mixture. The roof 
was constructed of ordinary reinforced concrete with about 3 inches 
of 10 per cent oil-mixed concrete placed on top. For months the 
roof of this vault was subjected to several feet head of water without 
showing any signs of leakage. Another vault in the north end of the 
Treasury, on account of leaking, had never been available for storing 
anything of value. Oil-mixed concrete was placed on the roof of 
this vault and it is perfectly dry at the present time. Numerous 
floors of the subbasement of the Treasury Building and in the new 
Bureau of Engraving and Printing, and a floor in the Office of Public 
Roads, have been constructed with oil-mixed concrete and have 
remained entirely free from dampness up to the present time. 
