22 PRACTICAL SILO CONSTRUCTION 



In the preceding table, A refers to the outside 

 diameter of the foundation, including footing; B to 

 the width of the footing or bearing course on the 

 soil; C to the thickness of the footing course, and 

 D to the thickness of the wall of foundation that 

 rests upon footing course, and extends to ground- 

 level. 



The foundation course should be placed of con- 

 crete that is not leaner than 1:2:4 of well-graded 

 sand and gravel or crushed stone. This is well 

 tamped, and allowed to harden permanently before 

 the walls of silo are erected upon same, otherwise 

 the weight of the concrete placed [upon the foun- 

 dation may develop defects in the foundation that 

 would not happen if it had ample time and oppor- 

 tunity to thoroughly cure before the walls were con- 

 structed above ground-level. 



Where the soil is firm the excavation can be em- 

 ployed to furnish the mold for the outside walls of 

 foundation, by cutting it down to the size desired; 

 the forms for the inside wall surface can then be 

 erected and the concrete placed. 



Where the forms will permit, the floor of silo can 

 be laid at the time the foundation is placed, and thus 

 form a part of same ; but, where the wall forms de- 

 mand supporting uprights inside the silo, the floor 

 must then be placed after the silo walls are com- 

 pleted. 



