EURAL ENGINEERING. 591 



sand to 60 lbs. limestone dust and 9.3 gal. of asphaltic cement, and the second 

 consisting of 7.6 cu. ft. of crushed trap rock, 4 cu. ft. of sand, 50 lbs. of lime- 

 stone dust, and 8.2 gal. of asphatic cement. 



A cement concrete section, comprising 2,837 sq. yds., was constructed of a 

 1:1J:3 mixture, using coarse aggregates of i in. to IJ in. gravel and i in. 

 to 1* in. crushed limestone. The proposed bituminous coating for this pave- 

 ment was omitted on account of cold weather. A similar section, comprising 

 2,011 sq. yds., was also undertaken. 



A section of oil-cement concrete, comprising 2,430 sq. yds., was constructed 

 using the same proportions and coarse aggregates as in the cement concrete. 

 Five pints of light residual petroleum per bag of cement were mixed with 

 the concrete. These surfaces when inspected in March, 1913, were in excellent 

 condition. In connection with these experiments observations are being taken 

 on the change in length of the concrete due to temperature and moisture 

 changes. The measurements are taken by means of a specially designed 10-ft. 

 strain gage on brass plugs embedded in the concrete. 



At Washington, D. C, the sui-faces of several sections of limestone macadam 

 were treated with tar preparations and oils for the purpose of obtaining com- 

 P'arative data on several well-known bituminous materials adapted to cold 

 surface treatment. In June, 1912, these surfaces were treated with the 

 molasses-lime mixture previously noted at a cost of 2 cts. per square yard. 

 This treatment was unsuccessful, and in October, 1912, the surfaces were treated 

 in 4 sections with refined water-gas tar preparation, asphaltic petroleum, residual 

 petroleum, and asphaltic petroleum under 60 to 75 lbs. pressure at respective 

 costs per square yard of 6.997, 7.574, 8.936, and 5.672 cts. When inspected in 

 March, 1913, all of these sections presented a satisfactory appearance. 



Supplemental reports are appended of experiments made at Che\'y Chase, 

 Md., in 1911 on the use of tars and native and oil-asphalt preparations and 

 on the use of refined semiasphaltic oil ; at Jamaica, N. Y., 1911, on the use of oil- 

 cement concrete, oil asphalt, tar, and fluxed native asphalt ; at Ithaca, N. T., 

 1909, 1910, and 1911, on the use of tar, oil, oil asphalt, brick, cement, and slag; 

 at New York, N. Y., and Ridgewood, N. J., 1910, on the use of oil-cement 

 concrete; at Boise, Idaho, 1910, on oil-gravel macadam: at Ames, Iowa, 1910, 

 on the use of oil-asphalt gravel ; at Knoxville, Tenn., 1910, on the use of tar 

 and oil preparations ; at Youngstown, Ohio, 1909, on the use of slag, slag and 

 lime, slag and waste sulphite liquor preparation, and slag and tar; at Newton, 

 Mass., 1908, on the use of asphaltic preparations, tar preparations, residual oil, 

 and molasses-oil-lime; at Garden City, Dodge City, Bucklin, Ford, and Inde- 

 pendence, Kans., 1908. on sand clay and oil asphalt earth roads ; and at Bowling 

 Green. Ky., 1907, on the use of Kentucky rock asphalt. 



Rock asphalts of Oklahoma and their use in paving, L. C. Snider {Olda. 

 Geol. Burvey Circ. 5. 1913, pp. 22, figs. 7). — Attention is called to the extent of 

 rock asphalts in Oklahoma which with 1 or 2 exceptions occur in the southern 

 one-third of the State. The asphalt-bearing rocks are sandstone and limestone 

 impregnated with bituminous materials in varying percentages. The results 

 of tests of the properties of these materials, as made by the Office of Public 

 Roads of this Department, ai'e given in tabular form. 



In spite of the abundant supply of raw material the Oklahoma asphalts have 

 not been used to any great extent for paving purposes, due largely to the 

 prevailing belief that they are not suited for paving. A comparison of the 

 analyses of sheet-asphalt samples and rock-asphalt samples show that the 

 rock-asphalt pavement has a lower but far more uniform bitumen in content 

 and composition, although the average composition of the bitumen is about 

 the same. The construction of rock-asphalt pavements is described, and from 



