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WISCONSIN BULLETIN 266 



be in proportion of one part of sand to two parts of stone. 

 Ordinarily it is found in just the opposite proportion. 



To obtain the strongest concrete with the minimum 

 amount of cement it is very important that the cement, sand 

 and gravel be properly proportioned. If bank-run gravel is 

 to be used and the mixture is in the proportion of one part 

 sand to two parts stone, a mixture of one part cement to five 

 parts of bank-run gravel would be sufficiently strong for the 

 walls and basement floors. For a reinforced concrete hay 

 mow floor, however, a mixture of one part cement to four 

 parts of gravel (1-4), should be used, together with the 

 proper amount of reinforcement. If the sand and gravel 



FIG. 19. A FORM FOR BUILDING A CONCRETE WALL 

 In building a concrete wall much depends upon having the bracing in the form of 

 sufficient strength and properly spaced. 



are separate, a good mixture to use for a wall is one part 

 cement, two and a half parts sand, and five parts stone or 

 gravel (1:2|:5), and a one, two, four (1:2:4) mixture in the 

 hay-mow floor where reinforcement is neccessary. 



Another essential for good concrete is proper mixing. The 

 entire mass should be so thoroughly mixed before water is 

 added that it will be of uniform color. Enough water should 

 then be added so that it will be of a rather sluggish con- 

 sistency. If too much water is added there is danger of sepa- 

 rating the particles in the process of placing, or of the heavy 

 stones sinking to the bottom and the cement and fine sand 

 coming to the top. No rocks larger than one-third of the 

 thickness of the wall should be placed in the center and pud- 

 dled down into the mass of concrete. If a smooth finish is 



