Why Do Slabs Crack?

Concrete is one of the most long lasting, economical building materials ever devised by man. When placed properly and in the right application it will last a long, long time. However, nothing good lasts forever and concrete is no exception. It will crack; it is just a matter of when. Take a look at the sidewalk, the driveway, even the floor in stores where the concrete is not covered with tile. They have cracks. driveway-crack

Some of those cracks appeared within hours of pouring. Others took many years to develop. So, if we can put a man on the moon why can we make concrete that won’t crack?

But My Slab is Already Cracked!

If you already have cracks, reading this article may be entertaining but it won’t help your cracks. (Level It can help though!) Without further ado, cracks fall into one or more of several categories: 1) plastic shrinkage 2) settlement 3) drying shrinkage 4)chemical 5) corrosion and 6) overload. Let’s look at these one at a time and see what causes them.

1) Plastic shrinkage cracks occur when water evaporates too quickly from the surface. This causes the top of the slab to dry more quickly than the bottom and they pull each apart. This is more likely to happen when it is hot, windy or there is low humidity.

2) Settlement cracks occur when the ground under the concrete moves. This can be the result of poorly compacted soil, the wrong kind of soil (sand), water erosion or tree roots.

3) Drying shrinkage occurs when a slab that is restrained is drying and shrinking. This usually does not occur on free floating slab. It is more of a problem when a slab is tied into another structure like a wall with rebar.

4) There are two ways that chemical reactions can crack concrete. The first is because the concrete itself contains aggregates or cements that simply are not compatible. The second one is when salt is put on a newly poured slab.

5) Corrosion occurs when concrete that contains steel re-bar or steel wire mesh gets wet and comes in contact with oxygen. The only way this can happen is when small cracks develop in the concrete due to one of the reasons stated above and channel water into the crack.

6) Concrete is designed to take a certain load. Most sidewalks and residential driveways are designed to take the weight of a car or small truck. If you should decide to back up a loaded tandem axle dump truck or an M-60 tank on your driveway, don’t be surprised if it cracks.

DFW Concrete Leveling Company

For those of you who this is too late for and you already have cracked pavement. I would not be doing my duty if I didn’t remind you that Level It can come out and fix your shifting, un-level concrete slabs caused from concrete cracks. Whether it’s your driveway, sidewalk, patio or foundation, we can help. Give us a call today, for a fast FREE estimate!

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