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CONCRETE IMPROVEMENTS 02 5500- <br />7 <br /> <br />C. Forms shall be carefully set to the alignment and grade established and shall <br />conform to the required dimensions. Forms shall be rigidly held in place by stakes <br />set at satisfactory intervals. Sufficient clamps, spreaders and braces shall be <br />installed to insure the rigidity of the forms. <br />D. Forms for back and face of curbs, lip of gutters and edge of walks, valley gutters <br />or other surface slabs shall be equal to the full depth of the concrete as shown, <br />noted or called for on the plans or detail drawings. Composite forms made up from <br />benders or thin planks of sufficient ply to ensure rigidity of the form in the shape <br />required may be used on curves and curb returns. <br />3.04 PLACING STEEL REINFORCEMENT <br />A. Bars shall be free of mortar, oil, dirt, excessive mill scale and scabby rust and other <br />coatings of any character that would destroy or reduce the bond. All bending shall <br />be done cold, to the shapes shown on the plans. The length of lapped splices shall <br />be as follows: <br />1. Reinforcing bars No. 8, or smaller, shall be lapped at least 45 bar diameters <br />of the smaller bar joined, and reinforced bars Nos. 9, 10, and 11 shall be <br />lapped at least 60 bar diameters of the smaller bars joined, except when <br />otherwise shown on the plans. <br />2. Splice locations shall be made as indicated on the plans. <br />B. Reinforcement shall be accurately placed as shown on the plans and shall be firmly <br />and securely held in position by wiring at intersections and splices and by using <br />precast mortar blocks or ferrous metal chairs, spacers, metal hangers, supporting <br />wires, and other approved devices of sufficient strength to resist crushing under <br />applied loads. Supports and ties shall be such as to permit walking on reinforcing <br />without undue displacement. <br />C. Reinforcing shall be placed so as to have the following minimum concrete cover: <br />Surfaces exposed to water 4" <br />Surfaces poured against earth 3" <br />Formed surfaces exposed to earth or weather 2" <br />Slabs, walls, not exposed to weather or earth 1" <br />D. Minimum spacing, center of parallel bars shall be two and one half (2-1/2) times <br />the diameter of the larger sized bar. All reinforcing shall be securely tied in place <br />prior to pouring concrete. Placing of dowels or other reinforcing in the wet concrete <br />is not permitted. <br />3.05 MIXING CONCRETE <br />A. All concrete shall be transit mixed in accordance with the requirements of ASTM <br />Designation C94. Transit mixed concrete shall be mixed for not less than ten (10) <br />minutes total, of which not less than three (3) minutes shall be on the site just prior <br />to pouring. Mixing shall be continuous with no interruptions from the time the truck <br />is filled until the time it is emptied. Concrete shall be placed within one hour of the <br />time water is first added. <br />B. Hand mixing of concrete for use in concrete structures will not be permitted. <br />7.A. - Page 26 of 121 <br />32