24 BULLETIN 230, U. S. DEPARTMENT OP 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 
in 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. — Kesults 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-mLxed 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 effective as a waterproofing agent under low pressures, 
when plastered on either 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 
