Deceinbei-, 1921. 



SCIENTIFIC AGRICULTURE. 



133 



Concrete for Permanence 



J. M. SMITH, Professor of Agricultural Engineering, University of Alberta. 



Concrete is now used in so many <Jif- 

 ferent ways about the farm that every- 

 one connected with agriculture s}u)uld 

 study its possibilities and learn how to 

 make use of this valuable building mat- 

 erial. 



This article is not in an}' way original. 

 It does not outline any specific details re- 

 garding the mixing and placing of con- 

 crete. It gives some references which 

 can easily be procured and consulted by 

 those who wish to learn something of the 

 use and abuse of the ingredients that go 

 into a concrete mixture. This informa- 

 tion should be on file and passed on to 

 those wishing to make practical use of 

 it on the farm. 



Ramsower in his book "Equipment for 

 the Farm and Farmstead," outlines in a 

 very concise and clear way some facts con- 

 cerning concrete : 



"Cement is the foundation of all con- 

 crete work. There are two kinds to be 

 found upon the market — natural cement 

 and Portland cement. 



"Natural cement is made from a rock 

 containing varying quantities of lime and 

 clay. The rock is first ground into fine 

 particles and then burned. The resulting 

 clinker is then reground into a very fine 

 powder known as natural cement. Inas- 

 much as the rocks from which natural 

 cement is made vary greatly in their com 

 position, the cement varies in its quality. 

 Natural cement, although it begins its 

 initial set more quickly than Portland 

 cement, never attains the ultimate 

 .strength that the latter does. It is some- 

 what cheaper in first cost, but Portland 



* The member of the Editorial Board for 

 the division of Rural Engineering is very 

 anxious that it should not be a one man 

 department. He will welcome any mat- 

 erial that may be sent in for publication. 

 There are a sufficient^ number of men 

 engaged in Rural Engineering work in 

 Canada to make this a real live depart- 

 ment. To accomplish this object it must 

 have their support in a material way. 



cement should be given the preference for 

 all kinds of concrete work. 



"Portland Cement takes its name from 

 the Portland rocks in England, from 

 which it was first made, in 1829. In the 

 United States it was first manufactured 

 in 1870, at Copley, Pennsylvania. Its 

 use has increased so rapidly that now the 

 output amounts to about 100,000,000 bbls. 

 per year. 



"Portland cement is inade from an 

 artificial mixture of comparatively pure 

 limestone or chalk, and clay or shale, the 

 active ingredients being lime, silica, and 

 alumina. The raw materials are first 

 mixed in the proper proportions and 

 ground to a rather fine powder. The 

 mixture is then fed into large rotary kilns 

 and heated to an extremely high tempera- 

 ture, the powder partially fusing and 

 forming clinkers. These clinkers are 

 then ground into a very fine powder 

 known as Portland cement. 



"Inasmuch as the quality and chemical 

 composition of the raw materials, as well 

 as the proportions in which they are 

 mixed, are actually controlled, the result- 

 ing cement is of uniform composition. If 

 the bags are exposed to dampness, the 

 cement becomes lumpy. If the lumps are 

 hard, the cement is practically worthless 

 and should not be used. It will keep in- 

 definitely if stored in a dry place. The 

 bags should not be piled on or very near 

 an earth floor. 



"Sand. In all concrete Avork some 

 coarse material, or aggregate, is used. A 

 fence post made of pure cement and water 

 would be very strong indeed, but its cost 

 would be prohibitive. The aggregate is 

 used solely to cheapen the cost of the ob- 

 ject made. Sand is sometimes called the 

 fine aggregate. That portion of the 

 aggregate, the particles of which are one- 

 quarter inch in diameter or under is cal- 

 led sand. For good concrete work, sand 

 must possess several characteristics. It 

 must be clean ; that is to say it must be 

 free from fine clay and from loam." 



An extract from a booklet b}^ Harold 



