CEMENT. 



Ki)ids — Cement is of three kinds, JN^atural, Puzzolau and Portland. 

 The Natural and Portland cements are usually found on the markets 

 in Missouri. Natural Cement is cheaper, weighs less and is not so strong 

 nor so reliable as Portland. Cements are often sjwken of and sold 

 in barrels. In this treatment, however, they w'ill be discussed in 

 bags or sacks. A bag of "Western Natural cement Aveighs from 85 to 90 

 pounds; Eastern Natural, about 100 pounds. A bag of Portland 

 Cement weighs 94 pounds, and in mixing it it is safe to assume one 

 (1) cubic foot per bag. Poor cement is dear at any price. Cement 

 is the binding material of the concrete, and a poor cement means a 

 poor structure. On all Avorks of magnitude the cement should be 

 tested after it is brought upon the Avork, but a test requirement is 

 impractical, and usually unimportant where cement is applied to 

 farm uses. The purchaser must, therefore, rely upon the retailer to 

 give him a good reliablG Portland cement of a standard trand. 



Manufacture — Natural cement is produced by calcimining rock from 

 certain localities wdiieli contain, without the mixture of any material, 

 such elements as will produce a cement having hydraulic properties. 

 Puzzolan cement is made of lime and iron slag. 



In the production of Portland cement certain raw materials are 

 crushed and dried, then mixed in the proper proportion, as determined 

 by chemical analysis, after which they are pulverized and intimately 

 mixed. The resultant is then fed into the upper end of a rotary kiln 

 (a long inclined cylinder, from 60 to 125 feet in length), which rotates 

 slowly. This resultant is subjected to intense heat during its journey 

 from the upper to the lower end of the kiln, passing out at the lower 

 end a thoroughly calcined and burned clinker. This clinker is then 

 ground to a very fine powder (the fineness of the grinding, to some 

 extent, determining the strength of the cement) and forms what is 

 known as Portland cement. 



Brief History — Ruins illustrate the use of lime and cements by the 

 ancients. Especially is this true of the Romans, who, it is supposed, 

 used a Puzzolan cement made from a volcanic material or dust. The 

 Egyptians used a lava that contained hydraulic properties as a cement. 

 The Incas of Peru used a similar cement, and evidences of the ancient 

 uses of cement are found in Spain. It was not until the dawn of the 

 19th century that the brains of England and France produced, almost 

 simultaneously, an artificial hydraulic cement, the beginning of the 



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