CHST Concrete, Masonry, and Formwork Safety — Questions and Answers
Question 1: Under OSHA 29 CFR 1926.703, who must design formwork shoring systems that support cast-in-place concrete?
- The project superintendent
- A qualified person such as a licensed engineer (Correct answer)
- The concrete subcontractor's foreman
- Any OSHA 30-hour certified worker
Correct answer: A qualified person such as a licensed engineer
OSHA 1926.703(a)(1) requires formwork shoring to be designed by a qualified person — in practice a licensed engineer — who accounts for construction loads, lateral pressures from fresh concrete, and dynamic effects. A foreman or 30-hour card holder does not meet this design standard.
Question 2: What is the minimum rated compressive strength concrete must achieve before formwork and shoring can be removed?
- The concrete must reach 3,000 psi regardless of design strength
- Sufficient strength to support its own weight and construction loads, as determined by a qualified person (Correct answer)
- 50% of 28-day design strength in all cases
- Formwork may be removed 24 hours after pour completion
Correct answer: Sufficient strength to support its own weight and construction loads, as determined by a qualified person
OSHA 1926.703(e) requires that formwork not be removed until the concrete has gained enough strength to support itself and any construction loads, as determined by a qualified person — typically via cylinder testing or maturity monitoring. There is no universal fixed time or single percentage threshold; it depends on mix design, curing conditions, and structural loading.
Question 3: OSHA requires masonry walls over what height to have adequate bracing to prevent overturning during construction?
- 6 feet
- 8 feet
- 10 feet (Correct answer)
- 12 feet
Correct answer: 10 feet
OSHA 29 CFR 1926.706(b) requires that masonry walls over 8 feet in height be adequately braced to prevent overturning and collapse until permanent supporting elements are in place. The 8-foot threshold triggers the mandatory bracing requirement.
Question 4: During a concrete pour, a form suddenly bulges outward at the base. The FIRST corrective action should be:
- Continue the pour and add wedges to the outside of the form
- Stop the pour immediately and evacuate workers from the affected area (Correct answer)
- Reduce the concrete pump pressure and continue at a slower rate
- Notify the engineer and await instructions before stopping the pour
Correct answer: Stop the pour immediately and evacuate workers from the affected area
Form bulging indicates imminent failure from excess lateral pressure. The immediate priority is life safety — stop the pour and evacuate all personnel from the hazard zone. Continuing the pour at any rate risks progressive collapse. Engineering consultation follows evacuation, not precedes it.
Question 5: What specific hazard does OSHA address in 29 CFR 1926.702 regarding bulk cement storage silos?
- Silica dust exposure during silo loading
- Engulfment hazard from entering an in-service silo (Correct answer)
- Noise exposure from pneumatic cement conveyors
- Electrical grounding of metallic silos
Correct answer: Engulfment hazard from entering an in-service silo
OSHA 1926.702(j) prohibits workers from entering bulk cement storage bins, tanks, or silos that are in service due to the engulfment hazard from flowing cement, which can bury a worker in seconds. This is analogous to grain entrapment in agriculture and is specifically addressed in the concrete subpart.
Question 6: A precast concrete plank is being set by crane. Under OSHA 29 CFR 1926 Subpart Q, workers may not stand on a precast section until:
- The crane tension is released and the tag line is removed
- It has been secured to prevent movement and a competent person has determined it is stable (Correct answer)
- The plank has been in position for at least 30 minutes
- At least two adjacent planks have been set to provide lateral stability
Correct answer: It has been secured to prevent movement and a competent person has determined it is stable
OSHA 1926.704(c) allows workers on precast elements only after the section has been adequately secured against movement and a competent person has determined stability. The standard focuses on secured position and competent-person determination, not on time elapsed or number of adjacent panels.
CHST Concrete, Masonry, and Formwork Safety
Under OSHA 29 CFR 1926.703, who must design formwork shoring systems that support cast-in-place concrete?