

MATERIALS USED IN CONS 

 AND CONCRETE 



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A, H. M. BAINER and H. B. BONEBRIGHT 



PART I. 



GENERAL STATEMENTS 



Con cut. In cement fence post construction, it is desirable 

 that the post be made as light and as strong as possible, and thus 

 it is practical to use nothing but the best grade of Portland 

 cement. 



Sand. Clean, sharp sand with grains varying in size from 

 small to large makes the best mixture. Sharp sand- is composed 

 of sharp, angular grains of all sizes and makes a better mixture than 

 that which is smooth and round, or "river-worn." 



A sand composed of fine and coarse grains mixed, is to be 

 preferred, because less cement will be required to fill the voids than 

 either used by itself. 



Leaves, sticks, stones or gravel should be removed by screening. 



Gravel. The same general rules used in the selection of a 

 good grade of sand will apply to gravel. It should be composed 

 of clean, sharp pebbles of all sizes. For post construction, the 

 pebbles must not be too large, as they will interfere with the proper 

 placement of reinforcement. 



Broken Stone. Broken stone used for post construction 

 must contain no large pieces as they will interfere with the place- 

 ment of the reinforcement. It is necessary to use sortie sand with 

 the stone to fill voids and thus save cement. It is not desirable to 

 use soft sandstone, soft limestone, slates, or shales. Granites, hard 

 limestones, and coarse gravel, which has been crushed, is considered 

 best. 



Water. The water used in making a cement or concrete 

 mixture should be clean and free from alkali or acids. 



Proportions. On account of the difference in the total 

 open space or voids in sands or gravel composed of different sized 

 particles and also that more cement is required in some conditions 

 than in others, it is often necessary to make a rough determination 

 of the percentage of voids to the total aggregate. Where maximum 

 strength is required about 10 per cent, more cement should be used 

 than the total voids. 



The determination may be made as follows : Secure a water- 

 tight box or pail of known capacity, fill it with the aggregate to be 

 used so that when it has been well shaken it will smooth off even 



* This bulletin is an abbreviated edition of Bulletin No. 148 of June, 

 1909. A large part of the details of the tests have been omitted, but all 

 the important results are summed up in the tables here presented. 



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