4 BULLETIN 105, IT. S. DEPARTMENT OF AGRICULTURE. 



Table 3. — Analyses of native and oit-asphult products used in the surface treatment of 



concrete. 



Materials. 



Fluxed native 

 asphalt. 



No. 1. 



No. 2. 



Oil asphalt. 



No. 1. 



No. 2, 



Sections 



Specific gravity 25°/25° C ^ 



Melting point ° C 



Penetration (25° C, 100 grams, 5 seconds [mm.]) 



Per cent of loss at 163° C, 5 hours (20 grams) 



Penetration of residue (mm.) : 



Per cent of total bitumen insoluble in 86° B. naphtha 

 Per cent of fixed carbon 



Per cent soluble in CS2 (total bitumen) 



Per cent of organic matter insoluble 



Per cent of inorganic matter insoluble 



C,D,and 

 I. 



1.045 

 39 

 18.4 



3.50 



6.3 

 19.60 



9.83 



1.043 

 48 

 14.8 



2.73 



6.4 

 21.87 

 11.17 



• 1.031 

 92 



12.6 



.32 



1.8 



34.84 



15.62 



1.012 

 52 

 14.7 

 .59 

 10.3 

 21.72 

 10.92 



94.70 

 1.23 

 4.07 



96. 56 

 1.35 

 2.09 



99.74 

 .17 

 .09 



99.72 

 .17 

 .11 



100. 00 



100.00 



1 Penetration (0° C, 200 grams, 1 minute) 1.4 mm.; penetration (46° C, 50 grams, 5 seconds) 5.8 mm. 



Experiment No. 4. — Oil-cement concrete. 

 Location : 



Station 30+90 to station 33+60, gravel aggregate. 



Station 42+50 to station 44+61, limestone aggregate. 



Station 46+10 to station 49+00, trap rock aggregate. 

 Total length: 771 feet. 

 Total area : 1, 744 square yards. 



Methods and materials. — Owing to irregularity in the delivery of 

 the materials, it became necessary to build experiments Nos. 4 and 5 

 in separated sections. The first two sections in the order above given 

 were completed in 1912, while the third was built in the spring of 1913. 



The concrete was mixed in a mechanical mixer of the self-propelled 

 rotary-distributor type. The proportions were 1 part of Portland 

 cement to If parts of sand and 3 parts of coarse aggregate, with 

 enough water to produce a concrete of quaky consistency 7 ". A light 

 residual petroleum having the characteristics given below in Table 

 No. 5 was mixed with the concrete to the amount of 5 pints per bag 

 of cement. This mixture was accomplished by delaying the intro- 

 duction of the oil until after the cement, sand, coarse aggregate, 

 and water had been partially mixed. The concrete was spread evenly 

 over the subgrade to a depth slightly greater than the finished thick- 

 ness of 6 inches and the surface was then "struck off" by means of 

 a well-designed "strike board." After this the surface was finished 

 to true grade and cross-section with a wooden float. The floating 

 was done from a bridge which rested upon the side forms and the 

 concrete gutter. Expansion joints were purposely omitted and no 

 joints of any other kind were constructed except those between the 

 days' work, and these were formed at an angle of SO degrees to the 

 center line of the road. Before continuing the work of laying the 



