86 BULLETIN 724, U. S. DEPARTMENT OF AGRICULTURE. 



ening tlie concrete of the foundation and tamping the concrete of the curb, to 

 insure that the curb will be firmly bonded to the base. The concrete shall be 

 well tamped and spaded along the forms, so that when they are removed there 

 will be no open and porous places on the sides of the curb. The top surface of 

 the curb shall be floated or troweled to a smooth finish. The forms for the curb 

 shall be smooth, clean, free from warp, and of sufficient strength to resist spring- 

 ing out of shape. They shall be well staked and braced, and the top edges shall 

 be at the same height and set true to line. To protect the curb from drying 

 out too rapidly it shall, within 12 hours after it is placed be covered with gunny 

 cloth, which shall be kept wet for five days. 



SEP ABATE CONCRETE CUEBS. 



Where the plans call for concrete curbs separate from the foundation they 

 shall be constructed before the subgrade is finally completed and shall have the 

 cross section shown on the plans. Such curbs shall be constructed in sections 

 not less than 6 feet and not more than 12 feet in length and shall be true to 

 grade and alignment. 



The specification already given for concrete curbs constructed in combina- 

 tion with the foundation shall also apply to curbs constructed separate from the 

 foundation as regards proportioning, mixing, and placing the concrete, con- 

 structing the forms, and all other features of construction which are not covered 

 on the plans or in this specification. 



STONE CURBS. 



Where stone curbs are recLuired, they shall be hauled and set before the 

 subgrade is finally completed. The curbs shall be set to line and grade and 

 shall be securely bedded in broken stone, gravel, or firm earth. In preparing 

 the trenches for the curbs great care shall be exercised to see the material 

 upon which the curb is to be set is well compacted, firm, and hard. 



Stone curbing shall be quarried from hard, tough, homogeneous stone. The 

 individual blocks shall have the cross section shown on the plans and shall be 

 not less than 4 feet in length. Each block shall be free from seams and all 

 other imperfections and shall be neatly dressed and finished on all exposed 

 faces. 



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