386 EXPERIMENT STATION RECORD. [Vol.40 



. RURAL ENGINEERING. 



Durability of cement draintile and concrete in alkali soils {Bngin. and 

 Contract., 49 (1918), No. 7. pp. 170-178). — This paper summarizes the results 

 of a third year's tests made under the auspices of the U. S. Bureau 

 of Standards. 



With reference to concrete, no definite conclusions arc as yet drawn at 

 its ultimate resistance to the action of alkali In the soils and waters on the 

 Irrigation projects, except to Indicate that materials of good quality and proper 

 workmanship are of the greatest importance. 



"The following conclusions may be drawn for the UE ement draintile 



exposed to soils or waters containing alkali salts in quantities of 0.1 per cent 

 or more: The use of cement tile in soils containing alkali -alls In large quan- 

 tities is experimental. Porous tile due to the use of lean mixtures or rela- 

 tively dry consistencies are - to disintegration. Some dense tile are 

 under certain conditions subjeel to surface disintegration. Disintegration Is 

 manifested by physical disruption caused by tl QSion resulting from the 

 crystallisation of salts In the pores and by softening, resulting from chemical 

 action of the solutions with the constituents of the cement. While results ob- 

 tained will not permit of a definite statement as to the relative effect of the 

 various constituents of the Baits, Indlcatioi eater the quantity 

 of sulphate and magnesium present and t!i • r the total concentration of 



salts the greater will be the disintegrating effect 



"Tile made by the pro.. Qmonly used, which allows the removal of 



forms immediately after casting, are Bubjecl to disintegration win- sed 



to soils or waters containing <U per cent or more alkali salts similar in com- 

 position to those encountered in this investigation. The band-tamped tile of 

 plastic consistency as made in this in < ;ual In quality to 



machine-made tile Of the same mixture, and they do not resist alkali action 

 lis well. 



"Steam-cured tile show no greater resistance to alkali action than tile which 

 are cured by systematic sprinkling with water. Tile made of sand cement have 

 less resistance to alkali action than the tile made of Portland cement of the 

 same proportions. The tar coating d is do :ve in preventing the 



absorption of alkali salts from the soil. The cement-grout coating is not 

 effective in preventing the absorption of alkali salts from the soil. No advant- 

 age is found in Introducing ferrous sulphate into the cement mixture. 



"If cement draintile are to be used in alkali soils or waters containing 0.1 

 per cent or more of salts similar in composition to those encountered in this 



Investigation, they should bo made of u' 1 quality aggregate in proportions 



of not less than l part Portland cement to :: parts aggregate. The consistency 

 should preferably be quaking, which has proved the most resistant of all mix- 

 tures used. This is wetter than that generally used in commercial tile plants 

 and will probably require the retention of the tile in the molds for several 

 hours, unless some means are found t<> hasten the hardening of the cement." 



Report of the committee on irrigation of the American Society of Agri- 

 cultural Engineers for the year 1917. O. W. ISBAXLSEN and II. 1'.. MusDOOX 

 {Trans. Amer. Soc. Apr. Bngin., 11 </.''/7), pp. 181-191: Redom. Bee. [U. 8.], 

 9 (1918). No. 4. pp. 170-174 ).— This report deals with economy in the use of 

 irrigation water, and summarizes answer- to a questionnaire relating to 

 the subject. 



The activated sludge experiments at Pasadena, Cal. {Bngin, and Contmot., 

 49 1 1918), No. 2. pp. 86, 37, figs. S). — In these experiments the plant consisted 

 of an aerating tank, one Bludge re-aerating tank, two settling tanks, and one 



