s 



Resistance is less for mortars with regular grains. 



As grains become smaller the resistance lowers. 



Vs'ht-n sand is mixed the resistance increases if there 

 Ice as many coarse grains as fine grains, maximum 

 being obtained by a perfectly graduated mix. 

 GRAVEL AND STONE. 



For reinforced work it should never be larger than % in. 

 when the reinforcement is of small sectional area. When 

 large sections are used 1*4 in. may be used. Sand should 

 be screened out so that the materials can be properly 

 proportioned. Stone should be free from argillaceous or 

 organic matter. 



PROPORTIONS. 



The richer the mixture, the greater the compressive 

 strength; the greater the impermeability, the greater the 

 change in volume. It is best to proportion by weights, 

 as cement is likely to be fluffed. See table on page 185. 



Table Deduced from Dr. Dyhcrhoff's Tests on Cubes 



f Mnrttir <in<l SliiiHjle Concrete. 



