Under Environmental Category, which condition is disallowed?

• A. Wood supports allowed in aggressive conditions.
• B. Plastic supports required in all climates.
• C. Metal supports allowed in aggressive conditions.
• D. Metal supports not allowed in aggressive conditions.

Answer: (D)

Environmental Category addresses how exposure conditions affect which support materials are acceptable. In aggressive environments, the focus is on preventing corrosion and degradation of supports used with concrete. Metal supports corrode quickly when exposed to moisture, chlorides, and sulfates typical of aggressive conditions, which can compromise both safety and surface quality. Because of that, metal supports are not permitted in aggressive environmental conditions. Wood and plastic options are used instead to avoid the corrosion risk.