By: Thomas H. Welby Published: October 2012

Safety Policy: Basics of Concrete and Masonry Construction Safety

Now and then it's a good idea to review the foremost safety and OSHA compliance concerns peculiar to your trade. While many of the concepts will be familiar, it's dismaying how often employers are cited for violating everyday, easily-complied-with stand-ards.

Safety "Rule One" for concrete and masonry work is that a load must not be placed on any portion of a structure, until a qualified structural designer has determined that the structure is capable of supporting it.

Concrete pour operations should be directly overseen by a competent supervisor. This should include a safety briefing to all employees, the inspection of forms and reinforcing materials, bracing, troughs, and Personal Protective Equipment, and conformity with relevant drawings and structural details. Protective head and face equipment should be worn, whenever concrete is to be applied using a pneumatic hose

Reinforcing steel for walls, piers, columns and other vertical structures must be adequately supported, and employers must take measures to prevent unrolled wire mesh from recoiling.

Laxity in protecting employees from impalement is a frequently-cited OSHA violation. All protruding rein-for¬c¬ing steel, onto or into which someone might fall, must be guarded. Use only hard plastic mushroom-type caps, or other approved devices (not paper cups, orange traffic cones, or tape). Guardrails, or other fall protection measures, should be implemented, to safeguard employees in areas from which they could fall onto rebar.

A restricted-access zone is required, where a masonry wall is being built. The zone should be as long as the wall under construction, and extend out from the base for a distance four feet greater than the height of the wall. The zone should be clearly marked off, and only employees actually working on the construction of the wall should be permitted in the area. The failure to create and enforce such a zone is another frequently-cited OSHA violation.

Similarly, post tensioning operations should be performed within a limited-access area, with access permitted only to employees essential to the tensioning operations.

To the extent practicable, elevated concrete buckets should be routed to eliminate, or minimize, risks to employees from falling concrete buckets. No one should be permitted to ride in a concrete bucket, or to work beneath one as it is being raised or lowered.

Formwork must be designed, fabricated, erected, supported, braced and maintained, so that it will not fail in supporting all vertical and lateral loads applied to it. Drawings and plans, including all revisions, for the jack layout, formwork (including shoring equipment), working decks, and scaffolds, must be available at the jobsite. Failure to comply with this requirement is frequently cited by OSHA inspectors.

Shoring (and reshoring) equipment must be inspected prior to erection, to avoid the use of damaged equipment, and to determine conformity with the formwork drawings. Erected shoring equipment must be inspected immediately prior to, during, and immediately after concrete placement. Damaged or weakened equipment must be reinforced at once.

Sills used for shoring must be sound, rigid, and capable of carrying their maximum intended load. All base plates, shore heads, extension devices, and adjustment screws must be in firm contact and secured, when necessary, with the foundation and the form. "Eccentric" loads on shore heads (anywhere other than where the shore head has been designed to accept them) must be avoided.

If single-post shores are "tiered," or placed one on top of another, additional requirements must be met. The shores must be designed by a qualified designer; vertically aligned; spliced to prevent misalignment; adequately braced in two mutually-perpendicular directions at the splice level (each tier to be diagonally braced in the same two directions); and inspected, after erection, by a qualified engineer.

The adjustment of single-post shores to raise formwork must not be made after the placement of concrete. Reshoring must be erected, as the original forms and shores are removed, whenever the concrete is required to support loads exceeding its capacity.

The steel rods or pipes on which vertical slip forms (i.e., forms jacked vertically during the placement of concrete) must be specifically designed for that purpose, and adequately braced where not encased in concrete. Forms must be designed to prevent excessive distortion of the structure during jacking. Jacks and vertical supports must be positioned in such a manner that the loads do not exceed the jacks’ rated capacity.

Jacks or other lifting devices must be provided with mechanical dogs, or other automatic holding devices, to support the slip forms, should there occur a failure of the power supply or the lifting mechanism itself.

During jacking, the predetermined safe rate of lift must not be exceeded, and the form structure must be maintained within design tolerances for plumbness. All vertical slip forms must be provided with scaffolds, or work platforms, where employees are required to work or pass.

Forms and shores must not be removed until the concrete has gained sufficient strength, based on compliance with conditions stipulated in the plans and specifications, or testing by an ASTM standard method, verifying sufficient compressive strength.

Precast concrete wall units, structural framing, and tilt-up wall panels must be adequately supported until permanent connections are completed. Lifting inserts for tilt-up wall panels must be capable of supporting at least twice the maximum intended load; inserts for other precise members must be capable of supporting four times the load. Lifting hardware must be able to support at least five times the maximum load to be applied or transmitted to it.

"Lift-slab" operations are subject to many requirements applicable to vertical slip form jacking operations. Jacking equipment (and all load-bearing components) must be capable of supporting at least 2-1/2 times the load being lifted, and must not be overloaded. Units must be designed to support the load, at any position, in the event of malfunction or power failure, and to stop lifting if overloaded.

All lift-slab operations must be pre-planned by an experienced professional engineer, with plans to include detailed instructions and sketches. The plans and designs must also provide for maintaining the lateral stability of the building or structure during construction.

No non-essential employee shall be permitted in the building or structure while any jacking operation is taking place, unless a licensed professional engineer, independent of the engineer who designed and planned the lifting operation, has determined from the plans that the building/structure has been reinforced sufficiently to ensure that, in the event of a loss of support at any jack location, such loss will be confined to that location. No non-essential employee shall be permitted beneath a slab, while it is being lifted.

Any masonry wall over 8’, if not supported by itself or by another structure, must be braced to prevent tipping over or collapsing. The bracing should be prescribed by a competent person or the project engineer, taking wind loads into account. The bracing must remain in place until the engineer of record has given written consent, and the wall is permanently supported by the rest of the structure. Failure to comply with these requirements is a frequent ground for OSHA citations.

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