Concrete has long been the go-to material for sidewalks because it's strong and cheap. The typical stretch of walkway can last decades; New Jersey sidewalks have an estimated lifespan of 75 years.

The concrete at the top left is brand new. The concrete sidewalk next to it could be 60 or more years old. Note it is not cracked; only the top layer has worn off. (Tim Carter) Perspective by Tim ...