Why are there cracks on sidewalks at regular intervals? What causes the irregular cracking on sidewalks?

Answer 1

The irregular cracking is actually the reason for the regular cracking :-)
The regular cracks are there to give the sidewalk panels a place to go when they start changing temperature and expanding or coantracting. This is what causes the irregular cracks (sometimes)
Sometimes the irregular cracks can be caused by the roots of a very large, nearby tree or something like an incredible impact.
For example in a neighborhood where i used to live, there was a large spot that always had a crack in it due to a major auto accident which sent a car rolling into the side of the concrete blocking used to make the sidewalk (the grass nearby was considerably lower than the top of the sidewalk). It cracked all the way accross and was repaired, but cracked angain almost every winter.

Answer 2

The cracks at regular intervals are to allow the cement to move without making a more unightly crack or in the case of bridge cracks to avoid cracks that cause structural problems. Ex when the ground freezes and the side walk will be able to move at the joints. The irregular cracks are ones that are caused by factors such as a poor concrete job( bad mix of concrete or not enouph expansion joints) or things like tree roots that heave the sidewalk up in a location too far from a joint or soil that has become unsupportive.

Answer 3

As said before, the 'dressed' cracks on the sidewalk are pre-determined areas for a crack to occur... pre-determined by the guy (or gal) that 'finished' the sidewalk. Generally, if you provide a weak spot in concrete, it will crack there. Cracking happens within 24-36 hours of every new sidewalk pour. Most of the time you will never see it because it is right where the finisher put it! If you have other issues under your sidewalk (like bad compaction of the base gravel or water erosion under the walk or...) then you will start to see secondary cracks appear in a random fashion, all over the flaw-affected area.

Answer 4

the cracks in regular intervals are called expansion seams. This allows the concrete to move without minimal cracking.
The other cracks are most likely from frost or freeze thaw cycles, and also can be from live load surcharges such as vehicles, etc.

Answer 5

Cements expand and contract with the changing of the weather--the regular cracks are designed to allow for those changes without irregular cracking--which happens anyway.

Answer 6

movements of th earth no one really knows this but we are having an earthquakes every second it is so small it doesnt hurt anyone or move anything if it was rated it woul probably be a 0.1

* good luck with your sidewalk *sidewalk can crack if they are old or air has deplated them or erosion of the earth

Answer 7

Was there rebar or wire mesh put in the concrete ?