Why concrete cracks
It would be impossible to pin one reason for concrete cracking, however one of the most common reasons for fracture cracks is due to “plastic shrinkage” Plastic shrinkage happens in concrete when there is a rapid loss of water from surface of the concrete before it has fully set. The problem with this is that the concrete on the surface dries or cures more quickly than the concrete underneath. When this happens the surface is separate from the rest of the concrete pour and over time these two different layers crack and delaminate as it were
To avoid this, you need to keep the surface moist. You can do this by covering the surface with burlap or plastic sheeting. This is most important during very hot days or high wind days and especially in direct sunlight. You would do this after the concrete has “set” in an effort to minimize unwanted impressions on the new concrete.
Additionally, lightly watering the concrete during the finishing process and continued after installation will help reduce the amount of water evaporating from the surface. Watering the concrete twice a day after the installation has had 24 hours to cure slows down the curing process and helps create a more durable concrete surface.
Concrete Cracking from Settlement
In Denver and the surrounding suburban areas we see a great deal of this, especially in the Ken Caryl and Highlands Ranch areas. This is due to shifting soils, the ground under the concrete actually moves. This is typically the case from a poorly compacted base. Taking the time to install road base or structural fill and then compacting the base before pouring the concrete is critical to avoid cracking from settlement issues.
Water can be an issue here as well. You will want to mitigate water around concrete installations. If water gets under the pad, it can start to create a void which will cause the ground underneath the concrete to move.
In addition to compacting the base and mitigating for water, you will want to avoid planting trees immediately next the concrete. Roots can grow underneath the concrete and cause heaving in the concrete.
Because concrete requires water which naturally evaporates, drying shrinkage will happen naturally. During the curing process there is a reduction in volume of the concrete, when that shrinkage is impeded or slowed down by supporting soils, adjoining structures or reinforcement, stresses develop within the concrete and as a result these stresses cause cracking in the weakest points of the concrete and cause it crack.
In an effort to control this, control joints should be used in an effort to direct the cracking. Control joints will create a weak point in the surface and will guide the cracking.
Proper preparation of the concrete, the base and really investing the time it takes to finish the concrete will absolutely help you in obtaining that beautiful finish that you are looking for. Denver Concrete Inc takes the time to really prepare every concrete installation so that these types of issues can be avoided. Whether you are using Denver Concrete Inc, another Denver Concrete Company or Contractor, or you are installing the concrete yourself, it is imperative that you oversee the process and make certain that you have taken all necessary precautions that you can.
In order to keep concrete from cracking, or at least minimizing it, take care with your concrete install. It doesn’t take a great deal of effort or knowledge to make certain that you have a compacted base, the forms are how you would like (straight lines, level concrete or sloping, etc). While concrete installation is definitely an art form, any layman can grasp the concept enough to make certain that the contractors they have hired are completing the project properly.