Why do sidewalks have blocks, instead of being solid?
In: 205
Concrete (and everything else) grows and shrinks with daily/seasonal temperature changes.
When concrete shrinks, the ground it’s sitting on pulls back against it, causing it to stretch. This causes it to crack.
When the concrete grows, it presses against the concrete next to it, and it gets crushed.
When you build a sidewalk out of concrete, you put contraction joints (pre-built “cracks”) every few feet so that the concrete cracks in a neat, predictable manner. You put expansion joints further apart (every [20?] feet or so) filled with softer material that allow the concrete to expand without crushing at the edges.
If you ever see a sidewalk that someone tried to pour without these joints, it will likely have ugly cracks spaced every few feet and will be all busted up at the ends.
Also, modestly sized sections are more manageable to pour than giant expanses of concrete.
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