FP-96 English Version - Eastern Federal Lands Highway Division

Section 565During concrete placement, provide positive support from the top for thereinforcing steel cage. Maintain the top of the reinforcing steel cage no morethan 6 inches above and no more than 3 inches below the required position.If the reinforcing steel cage is not maintained within tolerances, make acceptablecorrections and do not construct additional shafts until the method ofreinforcing steel cage support has been approved.565.07 Concrete for Drilled Shafts. Place concrete immediately after allexcavation is complete and the reinforcing steel cage is in place. Furnishconcrete conforming to Section 552 except as otherwise indicated herein. Forshafts constructed without drilling fluid, use class A structural concrete havinga slump of 7 ± 1 inches. For shafts constructed with drilling fluid, use classA structural concrete having a slump of 8 ± 1 inches. Use seal concrete forunder water placement. Do not use seal concrete above the freeze/thaw orwet/dry zone of the hole. Place underwater concrete according to Subsection552.11(e) except as modified herein. The method of underwater placement issubject to approval.Adjust approved admixtures for project conditions to ensure that the concretehas the minimum required slump for at least 2 hours. Submit trial mix andslump loss test results for concrete at ambient temperatures appropriate for siteconditions.Place each load of concrete within 2 hours of batching. Longer placementtime may be permitted if the concrete mix maintains the minimum requiredslump for longer than 2 hours. Do not retemper concrete that has developedits initial set.Place concrete in one continuous operation from bottom to top of the shaft.Continue placing concrete after the shaft excavation is full and until acceptablequality concrete is evident at the top of shaft. Before initial concrete set,consolidate the top 10 feet of the shaft concrete using acceptable vibratoryequipment. Finish the top of the shaft to +1 inch or -3 inches from the requiredelevation. For wet holes, do not consolidate until all water or slurryabove the concrete surface has been removed. Place concrete either by freefall, tremie, or concrete pump.(a) Free-fall concrete placement. Use free-fall placement only in dry holeswith an 25-foot maximum height of free-fall. The concrete shall fall directlyto the shaft base without contacting either the rebar cage or hole sidewall.515