284 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



ing. The patent forms being of steel plate enable a very smooth 

 job to be secured. 



Making and Handling the Concrete. 



Only a first-class Portland cement which has been stored in 

 a perfectly dry place should be used. The proportions of 

 cement and gravel will vary with different grades of gravel. 

 If broken stone is available and cheap, it may be used with sand 

 instead of gravel. To obtain the best grade of concrete the 

 gravel and sand must be clean and durable and the cement 

 must be in such a proportion as to nearly if not altogether fill 

 the voids or open spaces between the sand and gravel. To 

 obtain the strongest concrete with the minimum of cement the 

 sizes of the gravel should be in the right proportion and vary 

 from the largest to the smallest sand particles. 



If bank gravel is used, the proper proportion of cement to 

 use may be determined by the following method described in 

 "The Cement Workers Hand Book," by W. H. Baker: "Fill 

 a vessel of known capacity level full with the stone or gravel 

 and sand and thoroughly mix in the proportions wished for 

 use. This will usually be as the gravel comes from the bank. 

 This must be thoroughly soaked so as to absorb no more 

 water, but should not contain an excess. Now measure and 

 pour in as much water as the vessel will contain. The propor- 

 tion of the volume of water poured in to the volume of the pail 

 is the proper proportion of cement to gravel. This is quite 

 a simple method of determining the space that the cement 

 should fill to make a good dense concrete. Under average 

 conditions one part of cement to five of gravel is a good mix- 

 ture for silos. Stones as large as two inches in diameter may 

 be used to advantage." 



Another essential of good concrete is thorough mixing. 

 The whole must be so thoroughly mixed that there will be a 

 coating of cement over each particle of inert material. Enough 

 water should be added so that when the concrete is placed in the 

 forms the whole will quiver or tremble as it is tamped. Thor- 



