XVI. 



THR\ CONSTRUCTION OF MODERN SILOS 777 



sist of round iron rods arranged both vertically and horizontally CHAP, 

 and embedded in the concrete near the outer surface of the 

 wall. The vertical rods should be J inch in diameter, spaced 

 from 1 2 inches to 1 5 inches apart and extending from founda- 

 tion to top of wall. The horizontal rods should be ! inch 

 in diameter, spaced from 9 inches to 12 inches apart. They 

 should be in as long lengths as possible, hooked together at 

 ends so that each row forms a continuous band round the silo. 

 The horizontal and vertical rods should be securely wired 

 together at all points of intersection to form a rigid network of 

 iron. There are of course other methods of reinforcement, but 

 the above with a 6-inch thickness of concrete is simple and 

 sufficient for any silo up to say 18 feet in diameter and 30 feet 

 in height. To erect the walls it is necessary to have moulds 

 or forms curved to the same radius as the silo, one convex on 

 face placed inside the wall, and one concave on face placed out- 

 side the wall, the two 6 inches apart from each other with the 

 reinforcing rods between. A sufficient number of these forms 

 must be provided to go completely round the silo, and when they 

 are placed in position and firmly fixed, the concrete is gently 

 dropped into the space between them in layers of not more than 

 6 inches deep and carefully and thoroughly rammed. These 

 forms can be made of a rough framework of wood with a lining 

 of galvanized sheet-iron on the curved face to give a smooth 

 finish to the surface of the concrete. Each of the forms may be 

 of approximately the same size as the sheet-iron lining to avoid 

 waste, viz. 6 feet long by 3 feet wide. When the concrete 

 has sufficiently set the forms should be carefully removed and 

 refixed at a higher level and again filled with concrete and this 

 process repeated until the top of the wall is reached. It is an 

 advantage to have two sets of forms, so that the second and 

 succeeding rows can be placed in position before the next lower 

 is removed. The door openings should be formed as the work 

 proceeds, the reinforcement should be modified and strengthened 

 around the openings and a splayed recess should be left all 

 round on the inside into which the door will fit without any 

 framework of wood. The roof can also be of concrete, either 

 flat or cone shaped, and if so constructed the concrete should 

 be approximately the same thickness as for walls and with 

 similar reinforcement. 



