442 IOWA DEPARTMENT OF AGRICULTURE 



hollow, clay building blocks, such as have been commonly used extensively 

 in important buildings for years. It was originally designed with a 

 plaster coat of cement mortar both inside and outside. However, the ex- 

 perimental silo shown in Fig. 1 was not plastered either inside or out, 

 but simply washed on the inside with a cement wash, and, for the time 

 it has been in use, it has been entirely satisfactory, indicating that the 

 plastering is not necessary where a tile block is used which will resist 

 the weather. In fact, only two of the silos in the bulletin have been 

 plastered. It is to be noted that the durability of this silo will depend 

 directly upon the Quality of the blocks. Soft hlocks which have not 

 been properly burned should be guarded against. On the other hand, good 

 vitrified blocks are among the most reliable and durahle of all building 

 materials. 



It would be difficult to overestimate the advantages of curved blocks. 

 The only spoiled silage found near the walls of silo No. 1 was a slight 

 amount not exceeding one to four cubic feet, or .01 to .06 of 1 per cent 

 of the total amount. This spoiled silage was found in the recesses of 

 the wall, which was quite rough, due to the use of long, 16-inch, straight 

 blocks. A Vvorkman lays up the curved blocks more rapidly, and with 

 more satisfaction than the straight block. The wall is smoother inside 

 and out, which is of obvious advantage to the preservation of silage inside 

 and the appearance outside.* 



Five different sizes of blocks have been used in building these silos. 

 The different sizes are shown in Fig. 16. The first two on the right are 

 of the same size, but show two different positions in which they have 

 been used. They are each 4x5x12 inch blocks. If laid as shown at 

 A, they form a 5-inch wall, and each increases the height of the wall 

 four inches, but if laid as shown at B, they form a 4-inch wall, each 

 increasing the height of the wall by five inches. C, the next size shown, 

 is a 4x8x12 inch block, which for ordinary silo work has proven itself 

 more desirable than any of the other sizes used, as it forms a 4-inch 

 wall which is abundantly strong for the purpose and each block forms 

 an 8-inch portion of the wall. With this block less mortar is required 

 than with any other size block because it is the largest of the 4-inch 

 blocks commonly manufactured within the state. Thus the mortar 

 joints are fewer than in any of the smaller blocks, while they are fully 

 as far apart and narrower than in the case with any of the larger 

 blocks. Also it forms a warmer wall than the smaller size blocks, as 

 there is less material extending across the wall to conduct heat away 

 from the warm silage. It is also easier for the mason to handle, as he 

 can grip it in one hand conveniently, while a larger block is tiresome 

 to handle. Also in turning a circle with a thicker block, the outer joint 



*The curving of these blocks is not so difficult tJiat any manufacturer 

 should hesitate in doing it. Tlie authors make no pretense of being clay- 

 workers, but have personally helped to arrange a cutting table to bend these 

 blocks automatically. An outlay of a few dollars is sufficient to equip an 

 ordinary cutting table for this bending. Then no other extra labor is nec- 

 essary as the ends need not be cut radial and they will fit concave to con- 

 vex sides, thus little difficulty will be found in setting them in the kiln. 



