Which code governs the design and construction of reinforced concrete in the United States?

The design and construction of reinforced concrete in the United States is primarily governed by the ACI codes, specifically the ACI 318 "Building Code Requirements for Structural Concrete." This code provides comprehensive guidelines and standards that ensure the structural integrity, safety, and durability of reinforced concrete structures. ACI codes are widely adopted and serve as the basis for many local building codes across the country, making them fundamental to the industry.

While ASTM provides specifications for materials and testing methods related to concrete, it does not set forth design criteria. ISO presents international standards but is generally not applied within the U.S. construction framework for reinforced concrete design. AASHTO focuses on guidelines and specifications related to highway and transportation projects, but it complements rather than governs general reinforced concrete design practices outside that specific context. Hence, the emphasis on ACI as the primary governing body makes it the correct choice in this scenario.