492 EXPERIMENT STATION RECORD. [Vol.35 



for stakiTig, $21.71 for machine work in cutting trenches, $17.04 for tile, $4.15 

 for hauling tile, $2.09 for laying tile, and $1.58 for filling ditches, a total of 

 $16.65. 



Rational method of selecting types evolved for a comprehensive county 

 road system, W. W. Mark {Efigin. Rec, 73 {1916), No. 17, pp. 536-538, figs. 

 J/). — It is stated that traffic census, population, and property valuation are the 

 bases used in equalizing the cost for users when designing a county road system 

 in Illinois. Methods of using these factors in the economic selection of road 

 types are described. 



Recent developments in the building of concrete roads, W. D. Uhleb 

 {Municipal Jour., 40 {1916), No. U, pp. 481-483, figs. 3).— The conclusions 

 di-avi'n from the construction of a 12-mile model concrete road are given. 



It was found that the greatest strength commensurate with economy in cost 

 of mixing was obtained from a mix of 1^ minutes duration. 



"Another feature is the great variation in strength of 6-in. cubes of the regu- 

 lar mix, made up daily during the progress of the work and ser aside for testing 

 at periods of 7, 14, and 28 days, and 6 months. The 7-day compression test runs 

 from 1,065 to 3,633; the 14-day test, from 1,572 to 4,212; and the 28-day test, 

 from 2,362 to 5,361." 



It is concluded that i-in. joints filled with bitumen with edges rounded and 

 protected with bitumen are more satisfactory and economical than steel pro- 

 tected joints. It is further concluded that better results at the same cost may 

 be secured with a 5-in. side and 7-in. center thickness, using light metal fabric 

 reinforcing, than with plain concrete 6 in. thick at the side and 8 in. in the cen- 

 ter. It is stated in conclusion " that the essential features for a good concrete 

 pavement are a hard, dense surface, true to grade and cross section, free from 

 waves, depressions, and irregularities, and one which will insure uniform 

 wear." 



Various aggregates in test concrete road, W. H. Connkll {Engin. Rec, 

 73 {1916), No. 17, pp. 554, 555, figs. 4)- — -A- description of the construction of a 

 two-mile test pavement, made to test some of the latest theories an<l prac- 

 tice in concrete road construction, is given. 



A study of cracks in a concrete roadway at Indiana University, U. S. 

 Hanna {Engin. and Contract., 45 {1916), No. 15, pp. 357, 358, fig. i).— This is a 

 brief discussion of the cracks in a two-course reinforced concrete road. It Is 

 pointed out that " some [of the cracks] are almost certainly due to insufficient 

 lapping of reinforcement. Others appear to be due to failure to secure a sub- 

 grade of uniform density. Lack of proper drainage may also have had a part 

 in it." 



Concrete road construction in Oakland County, Michigan, M. De Gloppeb 

 {Municipal Engin., 50 {1916), No. 4< PP- 140-14^, figs. 6). — This is an article 

 dealing with the practical details of methods of construction employed on this 

 work. 



Second biennial report of the Department of Public Roads made to the 

 governor and general assembly of Kentucky, R. C. Tekkell {Bien. Rpt. Dept. 

 Pub. Roads Ky., 2 {1913-1915), pp 162, pis. 32). — This report covers the work 

 and expenditures, by counties, of the department in Kentucky from November 

 1, 1913, to November 1, 1915. 



Annual report of the Baltimore County [Maryland] roads engineer, W. G. 

 SucRO {Ann. Rpt. Roads Engin. Baltimore Co. [Md.] 1915, pp. 90, pi. 1, figs. 

 17). — This reports the activities and expenditures of the county roads engi- 

 neer's office on roads and bridges in the different districts of the county dur- 

 ing 1915. 



