590 EXPERIMENT STATION RECORD. [Vol.43 



deposited over the bottom. It is also evident that the formation of gas under 

 a dam is a potential souix-e of dani;er if the shape of the structure is such as to 

 confine the gas." 



Concrete consistency measured by the How table, G. M. Williams {J'Jngin. 

 Ncws-Rcc, S4 {1020), No. 22, pp. 10U-10J,r,, fujs. ^).— The so-called flow table 

 devised at the U. S. Bureau of Standards for measuring the flowability and 

 workability of concrete is described and tests reported. 



The apparatus consists of a metal covered table top which can be raised ver- 

 tically by means of a cam working at the end of a vertical post to which the 

 top is attached. The height of drop can be adjusted by means of a bolt at the 

 lower end of the shaft. A mass of concrete or mortar is molded at the center 

 of the table in a sheet metal mold which has the shape of a hollow frustum 

 of a cone. For aggregates up to 2 in. maximum size this cone has a height of 

 6 in. and upper and lower diameters of 8 and 12 in. For smaller aggregates 

 when made up in small quantities, a cone having a height of 3 in. and upper 

 and lower diameters of 4 and 6 in. is used. The mass of concrete is tamixid 

 Just sufficiently to completely fill the form, the form withdrawn, and the table 

 top dropped 15 times through a distance of i in. The mass flattens and usually 

 spreads concentrically. Two diameters at right angles to each other are 

 measured, the long and short if difference is apparent, by means of a self-read- 

 ing caliper which is so graduated that the sum of the two readings is the value 

 for flowability, which may also be calculated by dividing the new diameter by 

 the old and multiplying by 100. 



Five separate batches of 1 : 24 : 3i concrete were prepared with percentages 

 of mixing water ranging from 7 to li. Seven per cent resulted in a concrete 

 too dry for ordinary construction work, 9 per cent in a concrete which flowed 

 sluggishly in a steel chute which had an angle of 21°, 10 per cent furnished as 

 wet and fluid concrete as is ever needed in practice, and 11 per cent a sloppy, 

 segregating concrete difficult to properly sample. The added water in excess 

 of 10 per cent resulted in practically no increase in flowability as measured by 

 both the flow table and the steel chute. 



The advantages of the flow table over the slump metliod are stated as fol- 

 lows: The flow table accurately measures flowability or consistency of con- 

 crete, mortar, cement, or lime pastes for all consistencies varying from dry 

 masses, which have only a slight tendency to flow or change their shape when 

 acted upon by external forces, to those consistencies which are so fluid that the 

 water and laitance will flow away from the coarse aggregate. The relation be- 

 tween flowability and quantity of mixing water is practically a straight line rela- 

 tion for all workable and usable mixtures and consistencies. The stiffening of 

 a mass of concrete due to absorption of water by the aggregate, evaporation, 

 or setting of the cement is indicated by reduction of flow of the mass on the 

 flow table. 



Tests of solid and laminated wood sheet-piles (Engin. Ncivs-Rcc, 84 

 {1920), No. 25, pp. 1201, 1202, ftps. 3). — Studies conducted at Cornell University 

 on the relative transverse strength and stiffness of solid and compound or lami- 

 nated wooden sheet-piles under bending loads, and on the efficiency of three 

 types of fastenings, are reported. The data indicate the distinct superiority 

 of the solid over compound or laminated piles. 



The phenomena of drying wood, H. D. Tiemann {Jour. Franklin Inst., 

 188 {1919), No. 1, pp. 27-50, figs. 8). — ^An analysis is given of the internal 

 stresses which occur in wood during the progress of drying from the green 

 condition, together with a brief discussion of the physical properties which 

 affect these stresses. 



