34 BULLETIN" 249, U. S. DEPABTMENT OF AGBICTJLTUEE. 



ing is completed, the surface of the concrete shall be finished by floating it with 

 wooden floats. The finished surface shall be free from porous or open spots. 

 No portion of it shall be more than one-half ( $ ) inch below a template, cut to 

 the crown shown on the cross-section drawings, placed on the pavement at right 

 angles to the center line of the road, and no portion of it shall be more than one- 

 half (£) inch below a straightedge ten (10) feet in length or more than one- 

 fourth (i) inch below a straightedge three (3) feet in length, laid on the 

 pavement parallel to the center line of the road. 



Protection. — After the concrete surface has been finished, as above described, 

 it shall be entirely covered with canvas as soon as this can be done without 

 marring its surface. The canvas shall be kept wet until the concrete has set 

 to such an extent that the surface of the pavement will not be marred by men 

 walking upon it (about twenty-four (24) hours), and it shall then be removed. 

 Immediately after the canvas has been removed, the surface of the concrete shall 

 be covered with a two (2) inch layer of earth, which shall be thoroughly wet 

 with water immediately after it is placed upon the concrete, and shall remain 

 in place and be kept wet with water for at least two (2) weeks. It shall be 

 removed before traffic is permitted upon the concrete surface. During this 

 period of two weeks or longer, as the engineer may require, on account of 

 weather conditions, no traffic whatever shall be allowed upon the concrete. 



Forms. — The forms shall be smooth, clean, free from warp, of sufficient 

 strength to resist springing out of shape, of a width equal to the edge thick- 

 ness of the pavement, and so designed that the various sections may be fast- 

 ened together in such a manner as to prevent relative vertical movement of 

 the ends. The forms shall be set true to line and grade, shall be well staked 

 and braced, and shall have a firm bearing. 



Joints. — Joints shall be spaced thirty (30) feet apart where gravel is used 

 as coarse aggregate and fifty (50) feet apart where crushed stone is used as 

 coarse aggregate. They shall be perpendicular to the subgrade, extend entirely 

 through the concrete pavement, and be located at an angle of seventy-five (75) 

 degrees with the center line of the road. The joint shall be one-fourth (£) inch 

 in width, and the abuttiug ends of the concrete sections shall be separated by 

 asphaltic or tar felt one-fourth (|) inch in thickness extending the full width 

 and depth of the pavement. The surface of the concrete pavement on each 

 side of the joint shall be true to grade and cross section. 



The contract price for the concrete pavement shall be compensation in full 

 for furnishing all materials, laying, sprinkling, and protecting the concrete, 

 furnishing and setting all forms, constructing necessary contraction joints, 

 and doing all other incidental work. 



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