3<D2 FARM DEVELOPMENT 



struction will prove more economical than the arch top 

 for culverts. Less concrete is required, not only in the 

 top, but in the sides. The forms are simpler to build, 

 and the cost of labor is usually lessened. 



" In the construction of the flat top culverts it is neces- 

 sary to use in the tops about I per cent of steel in the 

 form of steel rods, bars, old railroad rails, beams, or the 

 patented forms of reinforcing bars. 



" The forms will generally be built of 2-inch lumber 

 surfaced on one side with tight joints to prevent 



escape of the mortar. These 

 will be reinforced at inter- 

 vals of 2 to 3 feet with 

 2 x 4*8. The weight of con- 

 crete tamped into place is 

 so great that unless the 

 forms are built rigid they 

 will bend or break under the 



Figure 177. Cement culvert with wing- load, and an Unsightly job 



will be produced. These 



forms should be left in place about two weeks at least 

 and for culverts 10 or 12 feet wide a longer time. 



" A very much better grade of concrete can be made 

 out of cement, sand, and broken stone than with the sand 

 and cement, and the proportions used would be : one part 

 cement, three parts sand, and six parts of the broken stone 

 for the sides, wing walls, bottom and foundations of the 

 culverts, and one part cement, two parts sand, and jour 

 parts of the broken stone for the top. 



" The rods should be embedded in the concrete very 

 close to the under side of the top and near the inside 

 of the side walls. For a culvert with a 4-foot clear span 

 the following dimensions are recommended: Thickness 

 of top 8 inches, reinforced with ^-inch corrugated bars, 

 spaced 8 inches center to center. If the sides are 4 feet 

 high above the foundation they should be 6 inches thick 



