- 3 - 



on spreaders carrying r.iore than one hoop, has been evident. One common 

 fault has been the reduction of effective area of the spreader strap by rivet 

 holes. Improvements that "have been noted include the use of continuous heavy 

 angles along the door opening, instead of spreaders, to v,h.ich the hoops are 

 attached. The angles are held by heavy rods across the door opening at suf- 

 ficiently mde intervals so as not to interfere T/ith the rem.oval of silage, 

 V/elding to strengthen riveted members is also in evidence. 



Plastic calking \ms placed in most of the horizontal joints of three 

 courses of staves in silo B8 to observe its effectiveness as a joint seal. 

 From this one test the value of the calking may be questioned, as there vre.B a 

 small amount of joint leakage in the bottom trio stave courses :\dth little to 

 choose between calked and uncalked joints. In any case, its value m,ust be 

 very pronounced to offset the cost of materials and application. 



Coatings 



To effectively seal the interior and protect the concrete sto.ve silos, 

 some 24 different coatings have been applied. The materials include asphalts, 

 coal tars, oils, paraffin wax, rubber paints, s^mthetic resins, special 

 plasters, varnish, and waterproofing. Results t3 date have not been too 

 promising. It has been difficult to get a lasting bond betvreen the coating 

 and the concrete. Tests of coatings are also underway in tile block silos 

 where difficulty has been experienced in maintaining the mortar joint and in 

 steel silos, More durable mortar must te found for block silos as the types 

 now used disintegrate rapidly ojid leave the reinforcing exposed to the action 

 of silage acids. This will reduce the area of steel and weaken the silo if 

 allov'ed to continue. 



Considerable A-orl': has been done in the past on the strength and 

 durability of concrete end concrete staves and protective coatings for concrete. 

 Probably the most extensive work along thi.s lino has been a cooperative 

 project betv/een the United States Department of Agriculture and the Agricul- 

 tural Exporimont' Station of the University of Minnesota under the direction of 

 Mr, D, G, Miller, The results of some of these tests pertaining in particular 

 to concrete stave silos were published as Paper llo, 1713, Scientific Journal 

 Scries of the University of Minnesota, YHiilo many moans of protecting con- 

 crete and mortar from acids have bo.;n studied, as yet no substitute for a rich 

 well-proportioned mix has been foun.d. 



The Portland Cement Association has cooperated with different state 

 agriculturfil experiment stations in making studies of various protective 

 coatings for masonry silos. As a result of their -vork they recommend several 

 coatings that may be effective for from 1 to 5 years. The American Concrete 

 Institute through its coramittees is also investigating means of prolonging 

 the useful life of silos. 



Pressures 



The equipment being used to measure pressures in silage was developed 

 by the Bureau of Agricultural Chemistry and Engineering, U, S, Department of 

 Agriculture, and is described in the Journal of the i\inoricrn Society of 

 Agricultural Engineers for June 1939, Silage pressures have been measured 



