specifications - FAACO - Federal Aviation Administration Contract ...

FTWIC-2235June, 2009D. Carting or wheeling concrete batches on completed concrete floor slab shall not bepermitted until the slab has aged at least four (4) curing days. Unless pneumatic tiredcarts are used, wheel the carts on timber planking so that the loads and impact aredistributed over the slab. Curing operations shall not be interrupted for the purpose ofwheeling concrete over finished slabs.3.06 DEPOSITING:A. The method and manner of placing shall prevent segregation or separation of theaggregate or the displacement of the reinforcement. Use drop chutes of rubber or metalwhen necessary. Prevent the spattering of forms or reinforcement bars if the spatteredconcrete dries or hardens before it is incorporated into the mass.B. Fill each part of the forms by directly depositing concrete as near its final position aspossible. Work the coarse aggregate back from the face and force the concrete under andaround the reinforcement bars without displacing them. Depositing large quantities atone point in the forms, then running or working it along the forms shall not be permitted.C. After the concrete has taken initial set, the forms shall not be jarred. No force or loadshall be placed upon projecting reinforcement.D. Deposit the concrete through vertical drop chutes of rubber or metal of satisfactory sizewhen operations involve placing concrete from above, such as directly into an excavatedarea, or through the completed forms, particularly in walls, piers, columns, and similarstructures. Drop chutes shall be made in sections or provided in several lengths so thatthe outlet may be adjusted to proper heights during placing.E. Concrete shall not be dropped free more than 5'. Place in continuous horizontal layerswith a depth of from 1' to 3', depending upon the wall thickness. Each layer shall be softwhen a new layer is placed upon it. No more than one (1) hour shall elapse between theplacing of successive concrete layers in any portion of the structures included incontinuous placement.F. Place required sections in one continuous operation to avoid additional constructionjoints.G. If excessive bleeding causes water to form on the surface of the concrete in tall forms,make the mix dryer to reduce the bleeding. In tall walls, place the concrete to a pointabout 1' below the top of the wall and allow to settle. Resume and complete concretingbefore set occurs.H. Place concrete slabs with a finished surface greater (steeper) than one (1) vertical to ten(10) horizontal from bottom to top.3.07 CONSOLIDATING:A. Compact each layer of concrete and flush the mortar to the surface of the forms bycontinuous-working mechanical vibrators. Vibrators which operate by attachment toforms shall not be used. Apply the vibrator to the concrete immediately after deposit.Move vibrator throughout the layer of the newly placed concrete, several inches into the03300-20