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002429 Durango Pumoing Plant. Stage 1 Amendment 00 I c. Place the last 2 feet or more of concrete below horizontal members or bevels with a 2-inch or less slump and thoroughly consolidate. d. Delay placing of concrete from 1 to 3 hours, but in no case, do not delay placement so long that the concrete placed before the delay is not readily penetrated by vibrators. e. Provide adequate consolidation in the concrete at the interface of the fresh concrete and the underlying plastic concrete when consolidating concrete which is placed over formed openings after the delay period has elapsed and placement resumes. f. Repeatedly penetrate and thoroughly reconsolidate with the vibrator the upper portion of the underlying concrete which was placed before the delay. I I. Use a non-vibrating slip-form for placing concrete on unformed slopes. Use a 2- 1/2 foot wide minimum, slip-form. Place and consolidate concrete ahead of the slip-form using internal vibrators to ensure complete filling under the slip- form. B. Cold Joints I. 2. Avoid cold joints when placing concrete in any part of the work. In the case of equipment breakdown or other unavoidable prolonged interruption of continuous placing when it appears that unconsolidated concrete may harden to the extent that later vibration will not fully consolidate it, immediately consolidate such concrete to a stable and uniform slope. If delay of placement is then short enough to permit penetration ofthe underlying concrete, resume placement with particular care being taken to thoroughly penetrate and revibrate the concrete surface placed before the delay. If concrete cannot be penetrated with a vibrator, then treat the cold joint as a construction joint if the design requirements are such that a construction joint is practical. Do not place concrete in rain sufficiently heavy or prolonged to wash mortar from concrete. 3. 4. 5. 6. A cold joint may necessarily result from prolonged heavy rainfall. C. Construction Joints I. If a construction joint will impair the structural integrity, repair the concrete in accordance with USBR M-47. 2. Repairs in some instances will include removal of all or a portion of the previously placed concrete and the Contractor will not be entitled to any payment for such work. D. Tooled Edges: Tool exposed edges of slabs and top edges of curbs to a radius of 1/4 inch. E. Consolidation Cast-in-Place Concrete 03300 - 25