234 FAKM BUILDINGS IN SOUTH AFRICA 



In order to secure water-tightness, the concrete should be put 

 in rather slushy, and then well jogged into place. By passing a spade 

 down between the concrete and the face of the inner form, the broken 

 stone may be pressed back from the form, leaving a layer of 1 : 2 

 mortar on the inner face of the wall. While doing this care must be 

 exercised not to wedge the form out of place with the spade. 



The floor may be laid after the walls have been completed, the join 

 between the floor and the lower part of the walls being formed as shown 

 at ABC, Fig. 183, so as to prevent leakage. The barbed wires in the 

 floor should be tightly stretched. 



The walls should be protected and kept wet, for about fourteen days 

 after completion, by hanging wet sacks over them and spraying with 

 water twice a day. The floor may be kept covered, for a like period, 

 with wet sacks or a layer of moist sand. 



The following quantities of materials will be required : — 



For the walls up to joint ABC : 55 bags cement, 7| cubic yards sand, 

 15£ cubic yards broken stone. For the floor: 30 bags cement, -i'l cubic 

 yards sand, 8*2 cubic yards broken stone. 



The amount of steel required can be measured up from the drawing. 



Two months should be allowed to elapse, after the completion of 

 the tank, before filling it with water, This gives the concrete time to 

 strengthen. 



The tank may be made larger in plan than shown, but, if this be 

 done, extra piers would have to be provided, so that the piers may not 

 be spaced further apart, nor further from the corners of the tank, than 

 specified in the plan, Fig. 180. 



