24 BULLETIN" 230, U. S. DEPARTMENT OF AGRICULTURE. 



and 8 inches long. The test consisted in pushing the rods through 

 the concrete, and the point of failure was taken at the drop of the 

 scale beam. 



Two kinds of bars were used — plain and deformed. All specimens 

 were tested at 28 days, and the results are plotted on figure 7. The 

 bond strength is decreased, and the decrease depends directly on 

 the quantity of oil in the mixture. It is evident that the bond 

 between plain bars and concrete is so seriously affected by the mixture 

 of oil that it would be inadvisable to use such a combination. The 

 bond of deformed bars is not so seriously affected, but is somewhat 

 decreased by the oil admixture. 



SUMMARY OF CONCLUSIONS. 



The following conclusions as to the effect of the oils used in cement 

 and concrete may be drawn from the foregoing investigations: 



(1) The tensile strength of 1:3 oil-mixed mortar is very little 

 different from that of plain mortar, and shows a substantial gain 

 hi strength at 28 days and at 6 months over that at 7 days. 



(2) The times of initial and final set are delayed by the addition 

 of oil; 5 per cent of oil increases the time of initial set by 50 per cent 

 and the time of final set by 47 per cent. 



(3) The crushing strength of mortar and concrete is decreased by 

 the addition of oil to the mix. Concrete with 10 per cent of oil has 

 75 per cent of the strength of plain concrete at 28 days. At the age 

 of 1 year the crushing strength of 1 : 3 mortar suffers but little with 

 the addition of oil in amounts up to 10 per cent. 



(4) The toughness or resistance to impact is but slightly affected 

 by the addition of oil in amounts up to about 10 per cent. 



(5) The stiffness of oil-mixed concrete appears to be but little 

 different from that of plain concrete. 



(6) Elasticity. — Results of tests for permanent deformation indi- 

 cate that no definite law is followed by oil-mixed concrete. 



(7) Absorption. — Oil-mixed mortar and concrete containing 10 

 per cent of oil have very little absorption and under low pressures 

 both are waterproof. 



(8) Permeability. — While the laboratory tests to determine the 

 waterproofing qualities of oil-cement concrete have not given uniform 

 results, those made on oil-mixed cement mortar containing 10 per cent 

 of oil have shown that such mortar is practically waterproof under 

 pressures as high as 40 pounds per square inch. All the tests, whether 

 in the laboratory or in construction work, indicate that oil-mixed 

 mortar is very effectivo as a waterproofing agent under low pressures, 

 when plastered on cither side of a porous concrete or masonry wall. 



(9) The bond tests show the inadvisability of using plain bar 

 reinforcement with oil-concrete mixtures. The bond of deformed 



