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Removal of Falsework Supporting Wide Culvert Slab

Removal of Falsework Supporting Wide Culvert Slab

Removal of Falsework Supporting Wide Culvert Slab

(OP)
Just wondering what the structural engineering group sees as the criterion (criteria) for removing falsework supporting a thick wide (10 m) culvert slab (one way steel). For instance, the Alberta Ministry of Transportation states:

Portion of Work Age or Minimum Strength
Arches and girders - 14 days (or 80% of 28-day strength)
Pier caps and beams - 5 days (or 50% of 28-day strength)
Columns - 1 to 3 days
Decks & Slabs - 5 days (or 50% of 28-day strength)
Vertical faces of supported elements - 12 to 24 hours
Walls over 3 m high - 2 days

I would think that these strengths are based on using OPC (ordinary Portland cement) concrete whereas today, in many cases the use of fly ash up to 50% are being used in concrete mixes which will delay the initial hydration potential of the concrete. Too, some specifications that use fly ash constituents in the 30 to 50% range will actually specify 90-day characteristic strength values rather than the more traditional 28-day values.

Your comments would be appreciated.

RE: Removal of Falsework Supporting Wide Culvert Slab

Right; leave it until it rots and falls down of its own accord.

Is there some pressing need for the falsework material elsewhere?

Mike Halloran
Pembroke Pines, FL, USA

RE: Removal of Falsework Supporting Wide Culvert Slab

Those numbers seem appropriate to me, fly ash or otherwise. For your culvert slab, 5 days or 50%, whichever comes latest, is reasonable for formwork removal, but not for applied loading.

RE: Removal of Falsework Supporting Wide Culvert Slab

(OP)
Mike - monsoon and needing to open channel for river diversion . . . so yes, there is some urgency but not of the material - don't personally care if, after the slab can support itself, the river takes the falsework for a ride (I care, but . . .)

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