Formwork and Shoring

Concrete before it sets is a liquid weighing about 150 pounds a cubic foot, pushing outward on everything holding it. A wall form is a pressure vessel and a deck form is a temporary structure carrying more load than the finished floor will.

Formwork failures happen during the pour, with the crew on and around it.

What the standard requires

1926.703(a)(1): formwork shall be designed, fabricated, erected, supported, braced and maintained so it can support without failure all vertical and lateral loads that may reasonably be anticipated.

And the one that gets missed — 1926.703(a)(2): drawings or plans, including all revisions, for the jack layout, formwork including shoring equipment, working decks and scaffolds, shall be available at the jobsite.

Available at the jobsite. Not in the office, not on somebody's laptop at home. If nobody can put their hand on them, the pour has a problem that has nothing to do with concrete.

Shoring

• Inspected before erection against the formwork drawings — 1926.703(b)(1).
• Damaged shoring comes out of service. A bent, kinked or gouged post is not a post any more.
• Erected to the drawings, plumb, braced, on a base that carries the load. A shore standing on soft fill or on a slab that is itself still green is not carrying anything.
• Nothing removed until the concrete has gained enough strength. That decision belongs to a person qualified to make it, based on tests or the engineer's criteria — not on how long it has been or how hard it feels.
• Reshoring goes in before the original shoring comes out where the drawings call for it, and it is inspected the same way.

During the pour

This is the dangerous hour.

• Somebody watches the forms and does nothing else. Their whole job is looking for movement, deflection, a bulge, a leak at a joint, a shore going out of plumb, or a wale starting to bow.
• Everybody knows the signal and the escape route before the truck backs in.
• Pour at the rate the design assumed. Filling a wall form faster than the design rate raises the pressure past what it was built for — one of the most common causes of blowouts.
• Do not stack material or park equipment on green slabs or fresh deck forms.
• Nobody works or stands under formwork during a pour unless they are essential and the design allows it.

And the rest of the pour

• Wet concrete burns. It is a strong alkali, and it works slowly enough that people kneel in it or leave it in a boot for hours and end up in hospital. Rinse it off, change wet clothing, and flush eyes for fifteen minutes.
• Never ride a concrete bucket — 1926.701(d) — and nobody works under one being elevated or positioned.
• Cap the rebar before the deck is walked. That is the other talk, and it applies here every time.