482 EXPERIMENT STATION RECORD. [Vol.43 



crowning and ditching, construction of culverts and small bridges, graveling 

 where most needed, and last, the construction of the larger bridges. The cul- 

 verts and small bridges should be of concrete of simple design requiring the 

 minimum steel, carpenter work, and lumber." 



Koad-buikling materials in Texas, J. P. Nash, C. L. Baker, E. L. Porch. 

 JR., and R. G. Tyler (Univ. Tex. Bui. 1839 (1918), pp. 159, pis. 8).— This report 

 contains information on the nature, distribution, and extent of the road-building 

 materials of the different counties of Texas, and includes data on mechanical 

 and physical properties and the different types and methods of testing. 



The most prevaTent road-building material in the State is gravel, but there is 

 also an abundance of limestone over a considerable area. In certain restricted 

 areas there is an abundance of granite suitable for the making of granite blocks. 

 Sand and clay suitable for sand-clay road construction occur in a numl)er of 

 localities. Along the coast and paralleling it as far inland as 100 miles, there 

 ai'e practically no natural deposits of satisfactory road materials, so that the 

 matter of constructing first-class highways in this country is a question of im- 

 porting materials. The most accessible material is the shell, dredged from the 

 Gulf. 



Aggregate proportions for equal strength concrete, A. N. Johnson 

 (Engin. News-Rec, 84 (1920), No. 20, pp. 96//-566).— Tabular data are given for 

 135 combinations of fine and coarse aggregates producing equal strength con- 

 crete, based on the fineness-modulus theory of proportioning concrete for 

 actual field use in concrete highway construction. 



Concrete beam tests, Northport unit. North Platte Project, W. H. Fisher 

 (Reclam. Rec. [U. S.}, 11 (1920), No. 4, pp. 175-178) .—Field tests of reinforced 

 concrete beams, made to determine the advisability of using local gravel as a 

 concrete aggregate for irrigation, canal, and lateral features, are reported. 

 The gravel used contained about 20 per cent of sandstone pebbles. 



" On nearly all these tests, the failure was in the mortar or mortar bond 

 on gravel except in those tests showing an ultimate stress near 2.000 lbs. per 

 square inch, where a few of the sandstone pebbles . . . were sheared. This 

 shows that as far as quality of coarse aggregate is concerned suitable concrete 

 would be made from this gravel for any and all required structures. All 

 beams that failed at the lower unit concrete stresses . . . seemed to carry 

 a larger percentage of the coarsest aggregate than those which failed at the 

 higher stresses." 



There was also a marked increase of strength, varying from 40 to 55 per 

 cent, in those beams which were covered Avith sand while curing as com- 

 pared to those of the same age and mix which were left exposed to the 

 weather. The 1 : 2i : 5 beams covered while curing for both 30 and 90 day 

 tests were stronger than the 1:2:4 beams of the same age that were not cov- 

 ered while curing. 



Concrete mixtures in alkali soils, C. J. Mackenzie (Jour. Engin. Inst. ■ 

 Canada, 3 (1920), No. k, pp. 176-181, figs. 5).— A historical review of the sub- 

 ject is given, and the details of experiments being conducted in Saskatchewan 

 are outlined, the results of which are to be reported later. These consist of 

 a series of actual field tests of concrete in the form and under conditions 

 found in practice, observations of structures in course of construction in 

 troublesome areas, and chemical and physical laboratory tests. 



Cement joints economical in cast-iron gas pipes (Pub. Works, Jf8 (1920), 

 No. 10, p. 214). — This is a review of a paper by W. M. Henderson presented at 

 a meeting of the Pacific Coast Gas Association, in which data from two years' 

 work in laying large quantities of cast-iron pipe 4 to 30 in. in diameter are 

 presented. The conclusion is drawn that the cost of cement mortar in hub 



