1Plastic Shrinkage Cracks
The earliest crack that may form is due to the process known as plastic shrinkage. Plastic shrinkage occurs most often when a concrete mix consists of too much water. Weather and temperature can also play a big part in the proper curing of a concrete slab or structure.
If the base beneath the concrete does not consist of the correct materials and is not properly packed the concrete will settle and crack over time. It is very important that a properly packed base is created prior to pouring a concrete slab, footing, or structure. Settling can also occur if a tree is removed and roots underneath begin to decompose. Even minor movements underneath concrete can cause cracking over time.
Heaving cracks are cracks in concrete that are caused by either movement underneath or by excessive freeze and thaw cycles. Sidewalks or driveways that lie over a tree root can result in cracks caused by heaving.
4Stress and Pressure Cracks
Pressure cracks are usually the result of too much weight being placed on top of a slab or against a concrete structure. Excessive weight can put too much stress on the slab or even alter the ground beneath the slab which can cause cracking. Concrete can also crack under tension. If a slab is attached to an adjacent structure, which settles or shifts, the slab may be forced to crack under the increased tension.
5Crazing and Crusting Cracks
If moisture evapourates too fast during the concrete drying and curing process, crazing cracks may appear. These cracks will be very minuscule and appear similar to a spider web spreading in all directions. Since these cracks are minor and only visible on the surface, they don’t pose a threat to the structure’s integrity. Crusting cracks are cracks that appear most commonly during the concrete stamping process. If temperatures are high, the top of the slab may cure faster than the bottom. Small cracks on the edges may appear when stamps are removed. As with crazing cracks, these small surface fractures do not affect the integrity of the slab structure.