When building a rebar cage, what is used to join steel pieces together?

The correct choice for joining steel pieces together when building a rebar cage is steel tie wire. Steel tie wire is specifically designed for this purpose; it is flexible, durable, and allows for easy handling during construction. By using steel tie wire, workers can securely fasten the rebar pieces together, ensuring that the structure maintains its integrity and proper alignment throughout the pouring of concrete.

While alternatives like welding rods and metal clamps can also be used in various construction applications, they are not typically utilized for rebar cages. Welding rods require a welding process, which may not be practical in all scenarios and adds additional complexity. Metal clamps can provide a temporary hold but are not as effective for the continuous and secure binding required in a rebar assembly. Binding tape, although useful in some contexts, is not strong enough for the structural requirements associated with rebar construction. Hence, steel tie wire is the most appropriate and effective choice for this task.