KUKAL ENGINEERING. 787 



Cement and its manifold uses, E. A. Tkego (Bien. Rpt. Kans. Bd. Agr., 19 

 {1913-14), pp. 44S-457, figs. 10). — Several of the uses of cement in farm struc- 

 tures are described and illustrated. 



Effect of iron and calcium on concrete sand, T. Sa\t:lle {Engin. News, 74 

 {1915), No. 26, p. 1242, figs. 2). — In connection with a study of New Hampshire 

 and Vermont sands aud gravels, it was found that sands containing iron par- 

 ticles made a stronger mortar than ordinary sand, and sand containing con- 

 siderable calcium carbonate made mortars stronger than those made from 

 standard Ottawa sand. 



Shrinkage and time effects in reinforced concrete, F. R. McMillan {Univ. 

 Minn. Studies Engin., No. 3 {1915), pp. ^i, p?.s. 3, figs. 17). — Tests of long dura- 

 tion under load on a Si by 30 in. by 12 ft. reinforced concrete beam of 1:2:4 

 mixture, four 4 by 5 by 42 in. reinforced concrete beams of 1:2:4 mixture, a 

 6 by 8 ft. concrete slab reinforced two ways and of 1 : 2^ : 4 mixture, and a 

 10 by 10 ft. concrete slab reinforced one way and of 1:2:4 mixture, are re- 

 ported, together with a test of three beams to determine the shrinkage under 

 variable conditions of curing. 



" With materials aud mixtures as used in these tests it is safe to predict a 

 shrinkage of from f to 1 in. or more in 100 ft. when exposed to the ordinary 

 dry air of a heated building. It can not be definitely stated when shrinkage 

 will cease under these conditions, but certainly not within a year. However, 

 from one-half to two-thirds of the amount indicated may be expected witliin 40 

 to 60 days after exposure to dry air. The effect of thorough wetting in the 

 early curing stage seems to have no effect in reducing the total shrinkage, the 

 only effect being to retard the beginning of the action, this in spite of the fact 

 that the strength of the concrete is materially increased by this treatment. 

 Slight changes in the moisture content in the air will retard the shrinkage or 

 even cause a swelling, which seems to warrant tlie belief that structures open 

 to the elements would never show the same total shrinkage as found in these 

 tests. 



" The continued slirinkage in beams and slabs acts to prodtice an increasing 

 deflection, though not to the same extent as the time yielding. The yielding of 

 the concrete under compressive stress with time ... is greater as the unit 

 stress is greater and seems to go on indefinitely. In these tests the deforma- 

 tion due to yielding was. found to be from three to five times that produced 

 immediately upon the application of the load. On the tension side of a beam 

 or slab the effect of time is to cause a gradual increase in the steel stress from 

 the breaking down of the concrete in tension or the failure of the bond. The 

 combination of the extension at the bottom and a shortening at the top pro- 

 duces in beams and slabs a continually increasing deflection. With the same 

 unit changes top and bottom the deflection is less the deeper the beam." 



The most important possibility indicated by these tests is considered to be that 

 of the production of high stresses in the longitudinal steel of compression mem- 

 bers. " The time yielding of the concrete under stress, combined with the ex- 

 cessive shortening due to shrinkage, may result in deformations from five to 

 fifteen times those expected from the ordinary calculations." 



Hydrated lime in concrete road construction {Good Roads, 48 {1915), No. 

 23, pp. 305-308, figs. 7). — This is a review of some of the work done with 

 hydrated lime in concrete pavement construction. The consensus of opinion 

 based on these service tests seems in general to favor the use of hydrated lime 

 on concrete roads. 



Apparatus for measuring' the wear of concrete roads, A. T. Goldbeck ( U. S. 

 Dept. Agr., Jour. Agr. Research, 5 { '916), No. 20, pp. 951-954, pi. 1, fig. 1). — 

 An instrument developed liy the author in the Oflice of Public Roads and Rural 

 39513°— No. 8—16 7 



