why do they intentionally put cracks in the sidewalk?

Question

you know about every meter there is a nice even lined crack in the sidewalk, why do the construction people do it?

Answer 1

When concrete gets hot it expands when it gets cold it contract so the put in expansion joints this way when the concrete moves and cracks it will crack in the joint, not the middle of the sidewalk or driveway.

Answer 2

They're sidewalk snakes!! Otherwise known as cracks in the pavement or road that have been filled with tar. Just like with real snakes, there are dangerous ones and relatively innocuous ones as well.

The worst kind are those that have been ground out by the highway maintenance crew, and then partly filled with a softer rubbery tar. This is done to stop the crack spreading, and the rubbery tar allows the road to expand/contract with changes in temperature. Unfortunately this is bad for skates in two ways - the grinding out often is done at a width that lets a skate wheel drop into the crack, but is still narrow enough to then grip the wheel tightly. The rubbery filling doesn't help either, since it gives and helps to catch wheels as well.

The innocuous sidewalk snakes are filled level with a much harder tar, and are thus relatively safe to skate over.

In general, approach with caution!

Answer 3

Expansion joints usually are a joint the full depth of the concrete and filled with a material to allow the slabs to push against it instead of the next slab. These joints can be pinned with dowel rods so that the slabs won't rise or settle away from the next.
Control joints are groves made in the concrete with a grooving tool, or they can be sawed with a special blade. This controls longitudinal cracking, which will stop at the control joint.
I usually put expansion joints every 20 ft. and control joints every 4 ft.

Answer 4

They do that because the concrete expands and contracts in the hot and cold weather. To not put breaks in the concrete every so often would cause the concrete to crack from expanding in the heat and contracting in the cold.

Answer 5

For expansion. Up north when the ground freezes and then in the spring when the ground thawes the ground gives and if the concrete cracks it will do so where the expansion joint is. Down south same thing except for the extreme heat and the unstable ground (SAND).

Answer 6

So taht as the stuff it is made of expands in the heat and shrinks in the cold, it wont crack or buckle. The gaps made deliberately allow some movement due to changes in temperature

Answer 7

Expansion joints!! For the hot weather. Geezzz. Watch the History or Discovery Channel.

Answer 8

So the water from rain or else where can travel to the streets, it's a process to allow the removal of water, so the sidewalks can be free of puddles...possibly

Answer 9

So concrete can expand in hot weather, and contract in cold weather. Without it, there would be breaks in the sidewalk, and it would need repair.

Answer 10

My guess would be so when the weather changes, it doesn't shift and upheave causing it to crack or crumble...and gee if they didn't put them there, how could we ever have have played "Step on a crack,you'll break your_____ 's back" ??!!?? lol