OIL-MIXED PORTLAND CEMENT CONCRETE. 3 



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. 



