224 



FARM BUILDINGS IN SOUTH AFRICA 



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juices is almost certain to occur across the junctions between the various 

 tiers of concrete, when the silo is filled with ensilage. 



It will be found inconvenient and inadvisable to work with long 

 lengths of vertical reinforcing bar. From 6 to 8 feet is long enough 

 for these. They should be arranged to break joint as much as possible, 

 i.e. so as not to approach the condition of there being anywhere a ring of 

 splices, formed by the joins between separate lengths of bar being all at 

 the same level. Similarly joins in horizontal bars should be arranged 

 to break joint vertically. The joins are detailed in Fig. 175. 



The inner face of the silo wall should be surfaced by "spading" 

 between the inner mould and the concrete, as explained on p. 135. This 



results in the formation of a dense, hard 

 face, which is resistant against the acid 

 silage juices. Fig. 174 shows a hardwood 

 spade for the purpose. 



The emptying-doors themselves are 



used as moulds for the emptying-door 



openings. These doors will then fit 



quite closely in place, provided that 



each door has been used to mould its 



own opening. The edges of the door, 



and of any additional mould necessary, 



should be well oiled or greased, with the 



object more of filling the pores of the 



wood than of forming a greasy surface film. 



Immediately around the doorways a 



rich concrete should be used which is 



free from broken stone, e.g., a mixture of 1 part cement to 2 parts sand 



would be suitable. 



Fig. 170, page 220, details the flange and reinforcement at the top of 

 the silo wall. A special crown will have to be added to the forms, 

 when in their highest position, in order to mould this part. 



Patching. — Occasionally, on account of careless spading, or owing to 

 a leak in the form having allowed the cement and sand to run away, 

 open spaces between the stones of the concrete are found on the forms 

 being raised. Such places should be patched immediately by first 

 removing all loose stones, and, if necessary, roughing the surface to 

 get a good bond, and then filling with a 1 to 2 cement mortar. The 



Fig. 174. 



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Fig. 175. 



