How long does concrete last?

It depends on the design life [50 -75 years?], the environmental & service conditions, and preventative maintenance practices.

Concrete is thought of as being permanent strong and very durable. In actuality it is a very complex, thermodynamically unstable and chemically reactive building material that continues to cure and become stronger for years. It is also vulnerable to many external influences!

To obtain maximum life cycle [make it last] there are dozens of protective measures that can be taken to make it Green. An understanding that concretes absorb water and expel internal chemistry for years is paramount to obtaining a long life.

That drop of water you put on the surface was absorbed into the interior through the Gel-Pore / Capillary System, present in all concretes. This path is formed when water in the mix comes to the surface during the initial set/curing phase [Bleed Water]. After curing, it's hard, we walk and drive on it, but water we put on the surface is absorbed back into it. This moisture carries contaminates: salts, acidic compounds and carbon dioxide to the interior. Lowering the High pH around steel reinforcement to a point that corrosion cells begin to form on the embedded steel in the matrix.

Internal chemistry allowed to migrate out to the atmosphere on the surface results in several deleterious conditions. ASR, efflorescence, ettringite are a few! This is also what blisters or "Burns" a coating off in a very short time. A paint designed to protect the concrete, doesn't stand a chance if alkali is coming to the surface to compromise the bond!

First step in obtaining a long lasting concrete is to Stabilize It by waterproofing, to fill the microscopic voids in the capillary system. Nothing going in and nothing coming out of it is a Great Start. In reducing Moisture and Oxygen content inside a concrete, you have eliminated two of the four conditions needed for corrosion to commence. A stabilized concrete will give longevity to this very volatile building material, make it Green and prolong it's service life substantially. Answer is: " It Depends On How You Treat It!"