8 BULLETIN 230, U. S. DEPARTMENT OF AGRICULTUKE. 



(4) When 240 cc. of the oil is heated in an Engler viscosimeter to 

 50° C, and maintained at that temperature for at least three minutes, 

 the first 100 cc. which flows out shall show a specific viscosity of not 

 less than 15 nor more than 30. 



(5) When 1 part of the oil is shaken up with 2 parts of hundredth 

 normal caustic soda, there shall be no emulsification, and upon 

 allowing the mixture to remain quiet the two components shall 

 rapidly separate in distinct layers. 



The general purpose of the above clauses is as follows: 

 Clause 1 eliminates compounded products in which the presence 

 of saponifiable oils would break down the strength of the cement. 

 Clause 5 has a similar purpose in eliminating certam straight petro- 

 leum residuals which readily emulsify with alkali, and seriously 

 impair the strength of the mortar to which they are added. Clauses 

 2, 3, and 4 combine to prevent the use of certain asphaltic oils which 

 prove detrimental to the strength of the concrete, and clause 4, in 

 particular, prescribes an oil of such viscosity as to be readily miscible 

 with the mortar, while still possessing sufficient body to render the 

 structure damp proof. 



METHOD OF MAKING. 



For most purposes where damp-proofing is required 5 per cent of 

 oil based on the weight of cement in the mixture is all that is neces- 

 sary. A bag of cement weighs 94 pounds, and consequently, for 

 each bag of cement used in the mixture, 4.7 pounds or about 2^ 

 quarts of oil are required. 



Let it be supposed that a batch of concrete requiring two bags of 

 cement is to be mixed in the proportions of 1 part of cement to 2 

 parts of sand to 4 parts of broken stone or gravel, together with 5 

 per cent of oil. Four cubic feet of sand are first measured out in a 

 bottomless box 12 inches deep and 2 feet on each side. On top of 

 the sand is spread the cement and these materials are mixed together 

 until they appear to be of uniform color. Water is then added to the 

 mixture and the mass again mixed to a mortar of mushy consistency. 

 Five quarts of oil are then measured out and added to the mortar, 

 and the mass again turned until there is no trace of oil visible on the 

 surface of the mortar. Particular care should be taken to continue 

 the mixing until the oil is thoroughly incorporated in the mixture. 

 Experience has shown that to insure the very best results the length 

 of time of mixing should be practically double that required when 

 oil is not used. The oil-mixed mortar is then combined with the 

 stone or gravel previously moistened and the mass is again turned 

 until all of the stone is thoroughly coated with the mortar and the 

 mass is uniformly mixed throughout. Should only oil-mixed mortar 

 be desired, the process is similar to that above described except that 

 no stone is added. 



