22 



BULLETIN- 724, XT. S. DEPAETMENT OF AGEICULTUEE. 



tially a sloping shoulder with a raised curb at the 

 figure 6. The first is adapted for use where the 

 natural surface of the ground closely, and there is 

 culty in securing the necessary width for road and 

 the road is located in a deep cut, on the other hand, 

 reason it is especially desirable to utilize the gutter 

 road surface, the second type should be employed, 

 construction is practically the same for both types 

 scribed briefly as follows : 



outer edge, as in 

 road follows the 



no especial diffi- 



gutters. Where 

 or where for any 



as a part of the 

 The method of 



and may be de- 



First, the foundation sliould consist of broken stone, gravel, or a good quality 

 of earth brought to the required shape and thoroughly compacted by rolling or 

 tamping, as in the case of cobble gutters. The location and probable demands on 

 the strength of the structure determine the expense justifiable in any case. 

 Where earth is used as a foundation in cold climates, great care should be 

 exercised to see that it is -well drained, as otherwise freezing may cause the 

 gutter to heave. 



CONCRETE GUTTER 



Di 



ROADWAY 



w 





1:2=4 concrete about 6" thick. 



Foundation of gravel, broken stone, or good quality earth. 



Fig. 6. 



Second, the gutter paving should consist of concrete mixed in the proportions 

 1 part f)f Portland cement to \\ parts of clean coarse sand and 3 parts of 

 crushed stone or gravel that Avill pass a. l^-inch screen and be retained on a 

 i-inch mesh screen. If the paving is merely to prevent erosion and will take 

 no traffic a 1-2-4 mix may be used. The concrete should be mixed to a rather 

 dry consistency so that it will hold its shape in the gutter, and should be thor- 

 oughly tamped until all the voids are filled and mortar flushes to the surface. 

 The surface then should be brought to a smooth, uniform finish by striking off 

 with a template shaped to conform with the cross section of the gutter and 

 floating with a wooden float. In the case of the curb gutter, the mortar should 

 be worked down into the face of the curb with a spade. 



Fourth, joints extending entirely through the gutter should be constructed at 

 intervals of about 20 or 30 feet. The joints may be made conveniently by 

 means of bituminous felt strips placed in the gutter during construction. The 

 bituminous felt, which should be about \ inch thick, is held in place with a 

 template until the concrete is against it. 



Fifth, after the gutter is finished as above de.scribed, it should be protected 

 from tlie drying action of the sun and atmosphere for about two weeks. This 

 is necessary to prevent the concrete from develojnng excessive shrinkage, crack- 

 ing, and l)eing damaged otherwise from too rapid drying out. One of the most 

 satisfactory ways of protecting the concrete is to cover it with canvas as soon 



