Anyone who has worked with concrete before is aware that most projects call for some kind of reinforcement. Why isn't concrete more durable? In a nutshell, concrete has an incredibly high compression strength but a low tensile strength. Concrete must therefore be strengthened in order to prevent breaking when it is bent or twisted. This reinforcement takes the form of rebar in almost all circumstances. However, what is rebar? (Hint: It's a combination of the words bar and reinforcing.) Rebar comes in more varieties of sorts, widths, and sizes than most people realize.
Rebar made of carbon steel is the most common kind. It is suitable for projects of practically all sizes and types. The main disadvantage is that it corrodes, and when it does, it expands and cracks the concrete. Rebar isn't the ideal option if it's probable that it'll be exposed to moisture or humidity.
Manganese dominates the alloy used to make European rebar. Because it is the most prone to bending, it is not recommended for projects that will be subject to tensile pressure or for places that undergo earthquakes. Typically, it is the most affordable.
Epoxy-coated black rebar is up to 1700 times more corrosion-resistant. However, the coating is brittle and is prone to chipping if the rebar is handled violently. The coating also raises the price a little.
Similar to carbon fiber, GFRP, or glass fiber reinforced polymer, is a composite. It won't corrode in the slightest, but it also won't permit field bends. If you're thinking about GFRP, be sure to compare costs per linear foot. Because GFRP is so lightweight, it offers a much greater value per pound than carbon steel does (but the price per kg difference can be shocking).
Similar to epoxy coating, galvanising also increased the corrosion resistance of black rebar. It is significantly more durable than epoxy coating, even though it only enhances corrosion resistance by around 40 times. It costs roughly 40% more than epoxy-coated rebar, though.
The most expensive rebar, typically 800 times as expensive as epoxy-coated rebar, is stainless steel. It is 1500 times more corrosion resistant than black rebar, far more damage resistant than epoxy, and even more flexible than galvanised rebar. However, it is overkill for the majority of projects and can be bent in the field. The value of stainless steel rebar, with the exception of very specific circumstances, does not outweigh the price.