Concrete Placement, Formwork, Rebar, and Impalement Controls

Concrete Placement, Formwork, Rebar, and Impalement Controls

Concrete work can appear routine because pours happen frequently, but the hazards are high-energy and time-sensitive. Wet concrete is heavy, pump lines can whip, buckets can swing, trucks back through tight areas, forms can fail, and workers may rush to finish before the mix sets. The CHST should view concrete placement as a coordinated operation involving equipment, temporary works, access, communication, chemical protection, and rescue planning.

Pre-Pour Planning

Before placement begins, confirm that the pour plan matches the field. Identify truck routes, pump location, hose route, crane bucket path, washout area, worker access, lighting, fall protection, rebar protection, and emergency access. Verify that workers know the placement sequence, rate of placement limits, stop command, and who has authority to pause the pour.

Concrete delivery creates traffic risks. Ready-mix trucks have blind spots, rotating drums, chutes, pinch points, and washout concerns. Backing should be controlled with spotters or designated routes. Pump trucks require stable setup, outrigger support, overhead clearance, line inspection, and communication between the pump operator and placement crew.

Pump Hose and Bucket Hazards

A concrete pump hose can move violently if air enters the line, a blockage clears, or pressure changes. Workers should not straddle the hose, stand in front of the discharge end, or wrap the hose around their body. The crew should maintain controlled footing and avoid placing the hose where it creates trip hazards near edges or openings.

Concrete buckets create suspended-load hazards. Use controlled lift paths, exclusion zones, clear signals, and landing methods that keep workers out from under the bucket and away from pinch points. Workers should not ride buckets or stand between the bucket and formwork. Tag lines may help control rotation if they do not pull workers into the load path.

Formwork, Shoring, and Rate of Placement

Formwork and shoring are temporary structures that must support construction loads until the concrete can support itself. They should be designed and installed according to drawings or manufacturer instructions, inspected before placement, and monitored during the pour. Missing ties, damaged shores, poor bearing, improper bracing, unauthorized modifications, or excessive rate of placement can lead to blowouts or collapse.

Do not remove forms, shores, or reshores based on convenience. Removal should follow the plan and account for concrete strength, load transfer, curing conditions, and construction loads above.

Rebar, Dowels, and Impalement Protection

Vertical rebar, anchor bolts, dowels, and form stakes can impale a worker who trips or falls onto them. Mushroom-style caps may provide scratch protection but may not provide impalement protection unless designed and installed for that purpose. Effective controls include engineered covers, troughs, bend-over methods where allowed, guarding, barricades, or caps rated for impalement hazards.

The CHST should pay attention to rebar near access points, ladder bases, edges, deck openings, formwork platforms, and concrete finishing routes. Workers carrying hose or tools may not see protruding steel at foot level. Rebar mats also create trip hazards and unstable walking surfaces, so access routes may require planks, platforms, or designated walkways.

Chemical, Silica, and Skin Protection

Wet concrete can cause serious skin burns. Workers need appropriate gloves, boots, eye protection, and hygiene controls. Contaminated clothing should be removed, and skin should be washed promptly. Cutting, grinding, or drilling cured concrete can generate respirable crystalline silica, requiring dust controls such as wet methods, local exhaust, respiratory protection where required, and housekeeping methods that do not dry sweep dust into the air.

CHST Stop-Work Decisions

Stop concrete placement when formwork shows distress, pump communication fails, workers enter the bucket fall zone, rebar impalement hazards are unprotected, trucks back without control, or the pour rate exceeds the plan. Pausing a pour may be inconvenient, but a form failure, hose whip, or impalement injury is far worse.

Exam Focus

For exam questions, choose controls that address the actual source of concrete hazards: engineered temporary works, controlled equipment movement, exclusion zones, impalement protection, and exposure prevention. PPE supports the plan but does not replace form inspections, pump control, or guarded protruding steel.