Final answer:
The object in question is likely a form of reinforcement or anchoring hardware used in concrete structures. This could be steel reinforcing rods, which are chosen for their compatible expansion rate with concrete and durability.
Step-by-step explanation:
The object described that is made from a non-corrosive plastic or metal and remains permanently in place after the concrete cures is likely a kind of reinforcement or anchoring hardware used in construction. Items like steel reinforcing rods (rebar) are commonly used in concrete because steel's coefficient of linear expansion is similar to that of concrete, which allows them to expand and contract at similar rates, thereby preventing stress and cracks in the concrete structures.
These fixtures serve a crucial role in the structural integrity of concrete constructions and are designed to be durable and resistant to environmental conditions. Non-corrosive metals or plastics are selected to prevent rust and corrosion, which could otherwise compromise the structure over time.